COMPROPORTIONATION-BASED AUTOCATALYTIC CYCLES AND RELATED METHODS
20250382173 ยท 2025-12-18
Assignee
Inventors
Cpc classification
B01J12/00
PERFORMING OPERATIONS; TRANSPORTING
C01B17/0456
CHEMISTRY; METALLURGY
B01J19/004
PERFORMING OPERATIONS; TRANSPORTING
International classification
B01J12/00
PERFORMING OPERATIONS; TRANSPORTING
B01J19/00
PERFORMING OPERATIONS; TRANSPORTING
C01B17/04
CHEMISTRY; METALLURGY
Abstract
The present disclosure provides autocatalytic cycles and chemical reactor systems in which the autocatalytic cycles may be conducted. Also provided are methods of identifying the autocatalytic cycles and methods of conducting the autocatalytic cycles, e.g., to produce a desired product. Regarding the methods of conducting the autocatalytic cycles, such a method comprises: carrying out a comproportionation reaction by reacting a first reactant M.sub.1 and a second reactant M.sub.2 to form a product M.sub.3, wherein M.sub.1, M.sub.2, and M.sub.3 each comprise at least one chemical element in common and the product M.sub.3 is produced in stoichiometric excess; and carrying out an auxiliary reaction by converting the product M.sub.3 to M.sub.1 or M.sub.2.
Claims
1. A method for conducting an autocatalytic cycle, the method comprising: (a) carrying out a comproportionation reaction by reacting a first reactant M.sub.1 and a second reactant M.sub.2 to form a product M.sub.3, wherein M.sub.1, M.sub.2, and M.sub.3 each comprise at least one chemical element in common and the product M.sub.3 is produced in stoichiometric excess; and (b) carrying out an auxiliary reaction by converting the product M.sub.3 to M.sub.1 or M.sub.2.
2. The method of claim 1, wherein the autocatalytic cycle does not comprise: a chemical reaction involving bromic acid and cerium ions as chemical species therein; reacting formaldehyde to form glycoaldehyde; oxidizing pyrite in an aqueous solution; oxidizing oxalic acid by permanganate; a chemical reaction involving iodous acid and chlorous acid as chemical species therein; and a chemical reaction involving mercury ions, iron ions, and colloidal mercury as chemical species therein.
3. The method of claim 1, wherein M.sub.1, M.sub.2, and M.sub.3 are different chemical species from one another.
4. The method of claim 1, wherein the at least one chemical element in common is in a high oxidation state in M.sub.1, in a low oxidation state in M.sub.2, and in an intermediate oxidation state in M.sub.3.
5. The method of claim 1, wherein the auxiliary reaction is an oxidation auxiliary reaction in which the product M.sub.3 is converted to M.sub.1 or M.sub.2 using an oxidant.
6. The method of claim 1, wherein the auxiliary reaction is a reduction auxiliary reaction in which the product M.sub.3 is converted to M.sub.1 or M.sub.2 using a reductant.
7. The method of claim 1, wherein a total number of chemical reactions in the autocatalytic cycle is not more than 5.
8. The method of claim 1, wherein a total number of chemical reactions in the autocatalytic cycle is 2.
9. The method of claim 1, wherein the autocatalytic cycle comprises at least two different comproportionation reactions, wherein the comproportionation reaction of step (a) is one of the at least two, and further wherein there is at least one shared chemical species among all chemical reactions within the autocatalytic cycle.
10. The method of claim 1, wherein at least one chemical reaction within the autocatalytic cycle consists of inorganic chemical species.
11. The method of claim 1, wherein all chemical reactions within the autocatalytic cycle consist of inorganic chemical species.
12. The method of claim 1, further comprising suppressing a side chemical reaction between a non-catalytic reactant of the comproportionation reaction of step (a) and a reactant of the auxiliary reaction of step (b).
13. The method of claim 12, wherein the suppressing step is carried out by kinetically separating the non-catalytic reactant and the reactant, spatially separating the non-catalytic reactant and the reactant, temporally separating the non-catalytic reactant and the reactant, or a combination thereof.
14. A chemical reactor system configured to conduct an autocatalytic cycle, the system comprising a reactor region in which (a) a comproportionation reaction is carried out by reacting a first reactant M.sub.1 and a second reactant M.sub.2 to form a product M.sub.3, wherein M.sub.1, M.sub.2, and M.sub.3 each comprise at least one chemical element in common and the product M.sub.3 is produced in stoichiometric excess; and in which (b) an auxiliary reaction is carried out by converting the product M.sub.3 to M.sub.1 or M.sub.2.
15. The chemical reactor system of claim 14, wherein the autocatalytic cycle does not comprise: a chemical reaction involving bromic acid and cerium ions as chemical species therein; reacting formaldehyde to form glycoaldehyde; oxidizing pyrite in an aqueous solution; oxidizing oxalic acid by permanganate; a chemical reaction involving iodous acid and chlorous acid as chemical species therein; and a chemical reaction involving mercury ions, iron ions, and colloidal mercury as chemical species therein.
16. The chemical reactor system of claim 15, wherein the system is further configured to suppress a side chemical reaction between a non-catalytic reactant of the comproportionation reaction of (a) and a reactant of the auxiliary reaction of (b).
17. The chemical reactor system of claim 16, wherein the system is configured to kinetically separate the non-catalytic reactant and the reactant, spatially separate the non-catalytic reactant and the reactant, temporally separate the non-catalytic reactant and the reactant, or a combination thereof.
18. The chemical reactor system of claim 17, wherein the reactor region is configured as two separate reactor regions in fluid communication with one another but which spatially separate the non-catalytic reactant into one of the two separate reactor regions and the reactant into the other of the two separate reactor regions.
19. The chemical reactor system of claim 17, wherein the reactor region is a flow reactor region comprising an inlet valve and an outlet valve and the chemical reactor system further comprises a controller configured to control operation of the inlet and outlet valves according to a temporal profile to prevent the non-catalytic reactant and the reactant from being present in the flow reactor region at the same time.
20. A method of identifying an autocatalytic cycle, the method comprising selecting a comproportionation reaction comprising a first reactant M.sub.1 and a second reactant M.sub.2 capable of chemically reacting to form a product M.sub.3 in stoichiometric excess, wherein M.sub.1, M.sub.2, and M.sub.3 each comprise at least one chemical element in common; and selecting an auxiliary reaction that is capable of converting the product M.sub.3 to the first reactant M.sub.1 or the second reactant M.sub.2, wherein the autocatalytic cycle does not comprise: a chemical reaction involving bromic acid and cerium ions as chemical species therein; reacting formaldehyde to form glycoaldehyde; oxidizing pyrite in an aqueous solution; oxidizing oxalic acid by permanganate; a chemical reaction involving iodous acid and chlorous acid as chemical species therein; and a chemical reaction involving mercury ions, iron ions, and colloidal mercury as chemical species therein.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Illustrative embodiments of the disclosure will hereafter be described with reference to the accompanying drawings.
[0010]
[0011]
[0012]
[0013]
[0014]
DETAILED DESCRIPTION
[0015] The present disclosure provides autocatalytic cycles and chemical reactor systems in which the autocatalytic cycles may be conducted. Also provided are methods of identifying the autocatalytic cycles and methods of conducting the autocatalytic cycles, e.g., to produce a desired product.
[0016] In an embodiment, an autocatalytic cycle comprises (or consists of) a comproportionation reaction coupled to an auxiliary reaction. The comproportionation reaction and the auxiliary reaction are distinct chemical reactions involving the conversion of chemical species (i.e., chemical elements or chemical compounds) to other chemical species.
[0017] The comproportionation reaction of the autocatalytic cycle is a chemical reaction comprising a first reactant M.sub.1 and a second reactant M.sub.2 capable of chemically reacting to form a product M.sub.3. The reactants M.sub.1 and M.sub.2 and the product M.sub.3 are generally different chemical species, but they each share at least one chemical element in common. The reaction of M.sub.1 and M.sub.2 produces M.sub.3 in a stoichiometric excess, e.g., M.sub.1+M.sub.2.fwdarw.2M.sub.3, but the exact stoichiometry depends upon the chemical species involved. In addition to M.sub.1 and M.sub.2, additional reactants may be involved in the chemical reaction. Additional reactants may be referred to herein as food species. Similarly, in addition to M.sub.3, additional products may be produced from the chemical reaction. Additional products may be referred to herein as waste species. In embodiments, the shared chemical element in M.sub.1, M.sub.2, and M.sub.3 exists in a different oxidation state in each of M.sub.1, M.sub.2, and M.sub.3. For example, the shared chemical element in one of M.sub.1 and M.sub.2 may exist in a high oxidation state (highest of M.sub.1, M.sub.2, and M.sub.3), the shared chemical element in the other of M.sub.1 and M.sub.2 may exist in a low oxidation state (lowest of M.sub.1, M.sub.2, and M.sub.3), and the shared chemical element in M.sub.3 may exist in an intermediate oxidation state (intermediate between M.sub.1 and M.sub.2). In such embodiments, the reactants may be referred to as M.sup.Hi and M.sup.Lo and the product in stoichiometric excess may be referred to as M.sup.Med.
[0018] The auxiliary reaction of the autocatalytic cycle is a chemical reaction different from the comproportionation reaction, and one that is capable of converting the product M.sub.3 to the first reactant M.sub.1 or the second reactant M.sub.2. Due to this chemical coupling of the comproportionation reaction and the auxiliary reaction, a closed loop, i.e., cycle, is formed. Moreover, because M.sub.3 (which is converted to M.sub.1 or M.sub.2) and M.sub.1 or M.sub.2 (which reacts to produce M.sub.3) function as both products and reactants, the cycle is autocatalytic. M.sub.3 and its conversion mate (i.e., M.sub.1 or M.sub.2) may be referred to as autocatalysts. The other of M.sub.1 and M.sub.2 may be referred to as a food species or non-catalytic reactant.
[0019] In embodiments, the auxiliary reaction is an oxidation auxiliary reaction comprising an oxidant capable of oxidizing M.sub.3 to M.sub.1 or M.sub.2. In embodiments, the auxiliary reaction is a reduction auxiliary reaction comprising a reductant capable of reducing M.sub.3 to M.sub.1 or M.sub.2. Such auxiliary reactions may be referred to as redox auxiliary reactions. The oxidant and the reductant may be referred to as food species. However, the auxiliary reaction need not be redox auxiliary reaction. An illustrative example of an auxiliary reaction that is not a redox reaction is the auxiliary reaction of cycle B4 in Table 3, below.
[0020] The autocatalytic cycle may be characterized by the number of comproportionation reactions and auxiliary reactions as well as the total number of chemical reactions that define the cycle. As many known autocatalytic cycles involve a large number of chemical reactions, e.g., greater than 6, it was unexpected that the inventors' methodology identified numerous comproportionation-based autocatalytic cycles composed of a few reactions, including only two reactions (a single comproportionation reaction and a single auxiliary reaction). However, the present comproportionation-based autocatalytic cycles may comprise a single (i.e., only one) comproportionation reaction or more than one comproportionation reaction (e.g., 2, 3). Similarly, the autocatalytic cycle may comprise a single (i.e., only one) auxiliary reaction or more than one auxiliary reaction (e.g., 2, 3). This includes a single oxidation auxiliary reaction or more than one oxidation auxiliary reaction as well as a single reduction auxiliary reaction or more than one reduction auxiliary reaction. More than one auxiliary reaction may be used, e.g., if more than one chemical reaction is necessary to convert the product M.sub.3 to the first reactant M.sub.1 or the second reactant M.sub.2. In embodiments, the autocatalytic cycle is characterized by its total number of distinct chemical reactions. The total number is at least two, but in embodiments, the total number is no more than 5, no more than 4, or no more than 3. This includes the total number being between 2 and 5, between 2 and 4, as well as 3, or 2.
[0021] The autocatalytic cycle may be characterized by the nature of the chemical species participating in the comproportionation reaction(s) and the auxiliary reaction(s). In embodiments, at least one chemical reaction within the autocatalytic cycle comprises an inorganic chemical species and thus, the autocatalytic cycles herein may be referred to as inorganic autocatalytic cycles. By inorganic chemical species it is meant a chemical species containing a non-carbon atom (the chemical species may include carbon and/or hydrogen, but at least one non-carbon, non-hydrogen atom is also present). This encompasses embodiments in which all chemical reactions within the autocatalytic cycle comprise an inorganic chemical species. This further encompasses embodiments in which at least one chemical reaction within the autocatalytic cycle consists of inorganic chemical species (i.e., none of the chemical species in the at least one chemical reaction is a chemical species containing only carbon and hydrogen). This further encompasses embodiments in which all chemical reactions within the autocatalytic cycle consist of inorganic chemical species (i.e., no chemical species containing only carbon and hydrogen are present). As demonstrated in the Example below, the inorganic chemical species are not particularly limited as the inventors have identified numerous autocatalytic cycles based on chemical elements found throughout the periodic table.
[0022] The autocatalytic cycles may also be characterized as being abiotic, by which it is meant that the autocatalytic cycle does not occur as a result of (or involve) a biological catalyst such as an enzyme. In embodiments, none of the underlying chemical reactions, i.e., the comproportionation reaction(s) and the auxiliary reaction(s) that define the autocatalytic cycle occur as part of a living organism's metabolism.
[0023] Specific, illustrative autocatalytic cycles are set forth in Tables 1-3, below (it is noted that Table 1 is a representative sampling of a more complete set of autocatalytic cycles included in Table 2). In embodiments, the autocatalytic cycle is as follows (see cycle 130 in Table 2, below):
##STR00001##
[0024] In embodiments, the autocatalytic cycle is as follows (see cycle 49 in Table 2, below):
##STR00002##
[0025] In embodiments, the autocatalytic cycle is as follows (see cycle B35 in Table 3, below):
##STR00003##
[0026] In embodiments, certain reactions are excluded from the autocatalytic cycles, including Belousov-Zhabotinsky reactions. In embodiments, the comproportionation reaction(s) of the autocatalytic cycle does not comprise a chemical species comprising bromine (e.g., bromic acid (HBrO.sub.3)), e.g., as a reactant. In embodiments, the auxiliary reaction(s) of the autocatalytic cycle does not comprise cerium ions, e.g., as an oxidant/reductant. In embodiments, the autocatalytic cycle does not comprise a chemical reaction (which may be either the comproportionation reaction(s) or the auxiliary reaction(s) or both) involving bromic acid and cerium ions as chemical species therein. In embodiments, the autocatalytic cycle is not cycle 209 in Table 2, below
[0027] In embodiments, the autocatalytic cycle does not comprise reacting formaldehyde to form glycoaldehyde. In embodiments, the autocatalytic cycle does not comprise oxidizing pyrite in an aqueous solution. In embodiments, the autocatalytic cycle does not comprise oxidizing oxalic acid by permanganate.
[0028] In embodiments, the autocatalytic cycle does not comprise a chemical reaction (which may be either the comproportionation reaction(s) or the auxiliary reaction(s) or both) involving iodous acid and chlorous acid as chemical species therein. In embodiments, the autocatalytic cycle is not cycle 215 in Table 2, below.
[0029] In embodiments, the autocatalytic cycle does not comprise a chemical reaction (which may be either the comproportionation reaction(s) or the auxiliary reaction(s) or both) involving mercury ions, iron ions, and colloidal mercury as chemical species therein. In embodiments, the autocatalytic cycle is not cycle 103 in Table 2, below.
[0030] As illustrated in
[0031] In an illustrative competitive autocatalytic network (e.g., see
[0032] The present disclosure also encompasses methods of forming or identifying any of the disclosed autocatalytic cycles. In an embodiment, a method of identifying an autocatalytic cycle comprises selecting a comproportionation reaction comprising a first reactant M.sub.1 and a second reactant M.sub.2 capable of chemically reacting to form a product M.sub.3 in stoichiometric excess; and selecting an auxiliary reaction that is capable of converting the product M.sub.3 to the first reactant M.sub.1 or the second reactant M.sub.2. M.sub.1, M.sub.2, M.sub.3 and the auxiliary reaction(s) are as defined above. The methods may be carried out using a device (e.g., a computing device) comprising an input interface, an output interface, a communication interface, a computer-readable medium, a processor, and an application. One or more databases (e.g., of chemical reactions), data repositories for the device, may also be included and operably coupled to the device. The computing device may be configured to carry out a thermodynamic assessment of the identified autocatalytic cycle to determine whether, and what conditions, may be selected to induce the underlying chemical reactions of the autocatalytic cycle. Alternatively, the methods may be carried out as described in the Example, below, which were used to arrive at the autocatalytic cycles listed in Tables 1-3. Thus, such methods may be used to identify other autocatalytic cycles. Confirmation that a candidate autocatalytic cycle exhibits autocatalysis may be conducted as described in the Example below, including by measuring acceleration and/or seed-dependence of the comproportionation reaction(s).
[0033] The present disclosure also encompasses methods of conducting any of the disclosed autocatalytic cycles. The methods involve carrying out the comproportionation reaction(s) and the auxiliary reaction(s) that define the autocatalytic cycle being conducted. Carrying out these reactions generally involves use of conditions that induce the underlying chemical reactions. The term conditions may refer to the environment under which the reactants/products are subjected, including environmental parameters such as temperature, pressure, atmosphere, use of light and its characteristics, flow rate (if applicable), mixing conditions, period of time, etc. The specific choice of environmental parameters depends upon the specific autocatalytic cycle.
[0034] The term conditions may also refer to suppression of side chemical reactions between non-catalytic reactants and food species of the relevant comproportionation reaction(s) and the auxiliary reaction(s). By way of illustration, an undesired side chemical reaction may be a direct reaction between a non-catalytic reactant of the relevant comproportionation reaction and the oxidant (or reductant) of the relevant auxiliary reaction. As further described below, this is illustrated in
[0035] Suppression of undesired side chemical reactions may involve kinetic separation, spatial separation, temporal separation (or combinations thereof) of certain non-catalytic reactants and food species, including between a non-catalytic reactant of the relevant comproportionation reaction, and the oxidant (or reductant) of the relevant auxiliary reaction.
[0036] Kinetic separation is illustrated in
[0037] Spatial separation is illustrated in
[0038] Temporal separation is further illustrated in
[0039] Thus, conditions may collectively refer to appropriate selection of environmental parameters and chemical reactor system configured to carry out the relevant comproportionation reaction(s) and the auxiliary reaction(s) that define the autocatalytic cycle being conducted. This includes the chemical reactor system being configured to achieve kinetic, spatial, and/or temporal separation as described above.
[0040] The present disclosure also encompasses any of the chemical reactor systems described herein. This includes chemical reactor systems configured to achieve kinetic, spatial, and/or temporal separation as described above. However, more generally, the chemical reactor system comprises a reactor region configured to contain the reactants/products of the comproportionation reaction(s) and the auxiliary reaction(s) that define the selected autocatalytic cycle and to induce these reactions. Other components typically included in chemical reactor systems may be used as well as components for achieving an appropriate set of environmental parameters and/or for suppressing side reactions as described above: e.g., separated reactor regions, inlets and outlets for delivering reactants/products to and from the reactor region(s), heaters, controllers, etc.
Example
Introduction
[0041] This Example focuses on a specific type of reactioncomproportionationas a way of enumerating chemical reaction networks with autocatalytic motifs across the periodic table. Comproportionation (alternatively referred to as con-, sym-, or synproportionation) may be defined as when two chemical species containing the same element with different oxidation numbers react to yield a product species with the same intermediate oxidation state (
[0042] As described below, a specific search strategy for CompACs was developed and this strategy was used to document 226 CompACs across 46 elements. As demonstrated below, each of the 18 groups, lanthanoid series, and actinoid series in the periodic table supports multiple CompACs. (See Tables 1 and 2.) 44 prospective abiotic autocatalytic cycles were also documented that do not necessarily involve redox reactions but can be interpreted as Broad-sense CompACs. Broad-sense CompAC makes use of a definition of comproportionation that only considers stoichiometry (as opposed to both stoichiometry and oxidation state). (See Table 3.) A full explanation of Broad-sense CompACs is given below. It was demonstrated that autocatalysis is a broadly existing phenomenon, as it can be manifested by multiple sets of reaction rules, under a wide variety of conditions, and through the coordination of relatively small numbers of reactions between simple chemical species. Reconceptualizing the parameter space of environmental conditions under which autocatalytic dynamics can be facilitated enables researchers to access the disclosed autocatalytic cycles under a broad array of laboratory conditions.
Methods
[0043] Following the formalism of CompACs described above (see
[0044] The identification of CompACs was organized into three distinct stages. In Stage 1 (Comproportionation Reaction Search), handbooks of chemical reactions and chemistry textbooks were reviewed to identify individual comproportionation reactions (including broad-sense comproportionation reactions). The main materials used were: ISBN 978-0-12-395590-6; ISBN 978-0-12-395591-3; ISBN 978-0-07-049439-8; ISBN 978-0-19-876812-8; ISBN 978-0-12-352651-9; ISBN 978-7-5369-3374-3; and ISBN 978-5-358-01303-2. When needed, translation tools such as https://www.deep1.com/translator and multilingual technical dictionaries were employed. In addition to these reference volumes, the Reaxys database (https://www.reaxys.com/) was used to search for reactions involving metal oxides, metal chalcogenides, and metal halides, and documented comproportionation reactions.
[0045] In Stage 2 (Auxiliary Reaction Search), the handbooks, textbooks, Reaxys database and translation tools described above were used to identify individual auxiliary reactions or reaction pathways that close CompACs, i.e., convert a product of an identified comproportionation reaction to a reactant thereof.
[0046] In Stage 3 (Reaction Condition Descriptions and Balanced Reaction Check), using the database assembled from Stages 1 and 2, a search for primary literature corresponding to the records obtained from Reaxys was conducted, specifically using the following websites to find historical literature lacking direct links to Reaxys: https://books.google.com/, https://babel.hathitrust.org/, https://archive.org/, https://gallica.bnf.fr/, https://www.gutenberg.org/. When needed, resources such as https://www.deep1.com/translator and multilingual technical dictionaries were consulted.
Results
[0047] Surprisingly, 226 CompACs were documented across the periodic table. Most do not involve organic molecules. Table 1 shows representative examples while Table 2 shows the extended list.). At least two CompACs were documented for each of the 18 groups, lanthanoid series, and actinoid series in the periodic table. Of these, most CompACs were composed of two reactions, and only eight CompACs consisted of four or more reactions.
[0048] Table 1. Representative examples of Comproportionation-based Autocatalytic Cycles (CompACs). The arrows in this table do not mean that the reactions
TABLE-US-00001 TABLE 1 Representative examples of Comproportionation- based Autocatalytic Cycles (CompACs). Group or Count of Series CompACs Representative CompAC Group 1 8 NaH + HCl .fwdarw. NaCl + H.sub.2 2 CuCl + H.sub.2 .fwdarw. 2 Cu + 2 HCl Group 2 2 Ca + CaF.sub.2 .fwdarw. 2 CaF 3 CaF + Sc .fwdarw. 3 Ca + ScF.sub.3 Lanthanoid 3 2 EuCl.sub.3 + Eu .fwdarw. 3 EuCl.sub.2 2 EuCl.sub.2 + Cl.sub.2 .fwdarw. 2 EuCl.sub.3 Actinoid 5 ThO.sub.2 + Th .fwdarw. 2 ThO ThO + Si .fwdarw. Th + SiO Group 3 2 2 YF.sub.3 + Y .fwdarw. 3 YF.sub.2 YF.sub.2 + CaF .fwdarw. YF.sub.3 + Ca Group 4 4 TiBr.sub.2 + TiBr.sub.4 .fwdarw. 2 TiBr.sub.3 2 TiBr.sub.3 + 2 HBr .fwdarw. 2 TiBr.sub.4 + H.sub.2 Group 5 18 2 VCl.sub.3 + V .fwdarw. 3 VCl.sub.2 2 VCl.sub.2 + 2 HCl .fwdarw. 2 VCl.sub.3 + H.sub.2 Group 6 11 Cr.sub.2O.sub.7.sup.2 + 6 Cr.sup.2+ + 14 H.sup.+ .fwdarw. 8 Cr.sup.3+ + 7 H.sub.2O 2 Cr.sup.3+ + 3 MnO.sub.2 + 2 H.sub.2O .fwdarw. 2 HCrO.sub.4.sup. + 3 Mn.sup.2+ + 2 H.sup.+ 2 HCrO.sub.4.sup. .fwdarw. Cr.sub.2O.sub.7.sup.2 + H.sub.2O Group 7 21 2 MnO.sub.4.sup. + 3 Mn.sup.2+ + 2 H.sub.2O .fwdarw. 5 MnO.sub.2 + 4 H.sup.+ MnO.sub.2 + 2 Fe.sup.2+ + 4H.sup.+ .fwdarw. Mn.sup.2+ + 2 Fe.sup.3+ + 2 H.sub.2O Group 8 5 Fe + 2 Fe.sup.3+ .fwdarw. 3 Fe.sup.2+ 2 Fe.sup.2+ + Cl.sub.2 .fwdarw. 2 Fe.sup.3+ + 2 Cl.sup. Group 9 6 Co.sub.3O.sub.4 + Co .fwdarw. 4 CoO 6 CoO + O.sub.2 .fwdarw. 2 Co.sub.3O.sub.4 Group 10 7 NiS.sub.2 + Ni.sub.3S.sub.2 .fwdarw. 4 NiS 3 NiS + H.sub.2 .fwdarw. Ni.sub.3S.sub.2 + H.sub.2S Group 11 9 Cu + Cu.sup.2+ .fwdarw. 2 Cu.sup.+ Cu.sup.+ + Fe.sup.3+ .fwdarw. Cu.sup.2+ + Fe.sup.2+ Group 12 7 Hg + Hg.sup.2+ .fwdarw. Hg.sub.2.sup.2+ Hg.sub.2.sup.2+ + 2 Fe.sup.2+ .fwdarw. 2 Hg + 2 Fe.sup.3+ Group 13 14 2 B.sub.2O.sub.3 + 2 B .fwdarw. 3 B.sub.2O.sub.2 B.sub.2O.sub.2 + 2 H.sub.2 .fwdarw. 2 B + H.sub.2O Group 14 22 C + CO.sub.2 .fwdarw. 2 CO 5 CO + I.sub.2O.sub.5 .fwdarw. I.sub.2 + 5 CO.sub.2 Group 15 25 HNO.sub.2 + HNO.sub.3 .fwdarw. 2 NO.sub.2 + H.sub.2O 2 NO.sub.2 + Cu + 2 H.sup.+ .fwdarw. 2 HNO.sub.2 + Cu.sup.2+ Group 16 32 SO.sub.2 + 2 H.sub.2S .fwdarw. 3 S + 2 H.sub.2O S + O.sub.2 .fwdarw. SO.sub.2 Group 17 21 HCl + HOCl .fwdarw. Cl.sub.2 + H.sub.2O Cl.sub.2 + H.sub.2 .fwdarw. 2 HCl Group 18 4 XeF.sub.4 + Xe .fwdarw. 2 XeF.sub.2 XeF.sub.2 + F.sub.2 .fwdarw. XeF.sub.4 The arrows in this table do not mean that the reactions are irreversible but are intended to indicate the autocatalytic direction. Autocatalysts are shown in bold. For the extended list of CompACs, please refer to Table 2, below. Comproportionation reactions are shown by the upper equations, while the auxiliary oxidation or reduction reactions are shown by the lower equations.
[0049] As the term comproportionation does not necessarily require the reactants and products to follow the oxidation state pattern shown in
[0050] Identification of the CompACs helpfully assesses the distribution of autocatalytic stoichiometry throughout the periodic table, but does not consider the thermodynamics of the constituent reactions. Thermodynamic considerations bring to attention two potential issues. First, for a reversible reaction which is a part of a CompAC, its rate constant(s) in the autocatalytic direction may be much smaller than that of the reverse direction under a given set of environmental conditions, such that the autocatalytic process could be very slow or the steady-state concentrations of the autocatalysts could be very small. Second, a CompAC's comproportionation process and its auxiliary process may require very different environmental conditions to make them thermodynamically feasible. However, both of these issues may be addressed by applying a wide range of environmental conditions, or through spatial and temporal mechanisms capable of organizing reactions requiring different conditions into activated CompACs. Such considerations will be discussed below.
Discussion
[0051] Based on the strategy described above, empirically testable CompACs/Broad-sense CompACs were documented in all groups, the lanthanoid series and the actinoid series in the periodic table. This Example focuses on CompACs/Broad-sense CompACs consisting of just a few (mostly two, and no more than five, see Table 2: Serial 146) reactions, to allow for experimentally testing and coupling multiples of them together to form a more complex, ecosystem-like network. The broad prevalence of CompACs/Broad-sense CompACs across the periodic table suggests that, despite the challenges in searching for autocatalysis in any given reaction network, generic chemical circumstances or attributes are likely to exist that are correlated with a potential for autocatalytic behavior.
[0052] The composition of many of these CompACs/Broad-sense CompACs (Tables 1-3) at first seem tangentially relevant to living organisms (i.e., as opposed to biotic autocatalytic cycles). Some CompACs/Broad-sense CompACs center involve chemical elements that are absent or very rare in most organisms (e.g., Th and Hg); some are unlikely to occur under ambient terrestrial pressure or temperature conditions; and some produce chemicals that are deleterious or lethal to living organisms. They are nevertheless relevant for exploring the origins of life and the distribution of complex chemical dynamics in various astrochemical and exoplanetary locales. First, the conditions under which life originated may be dramatically different from what living organisms are dealing with today, and extraterrestrial life may be Compacc's very different from life on this planet. Coupling of CompACs/Broad-sense CompACs to organic chemistry, in a variety of different environmental contexts, could encompass a subset of reactions suitable for the sustenance of alternative life-like chemical systems. Secondly, abiotic CompACs/Broad-sense CompACs might have played critical roles during life's emergence but were subsequently lost from living organisms later, becoming the missing links, analogous to how construction scaffolds are removed after houses are built. Third, even if some CompACs/Broad-sense CompACs are not relevant to life either as we know it or in a form yet to be known, they may nevertheless generate secondary or tertiary chemical effects that may be misinterpreted as false positive biosignatures. Any and all of these conditions may be leveraged to engineer life-like chemical systems with useful chemosynthetic and information-processing properties.
[0053] Emergent Patterns from Interactions between CompACs. As illustrated in
[0054] In contrast to autocatalytic cycles observed in biochemistry that may involve dozens of reaction steps and/or, CompACs are much simpler since they usually consist of only two or three reactions. Such simplicity may be important for a primitive life-like autocatalytic system to emerge and persist. An autocatalytic cycle with fewer reaction steps tends to have a higher carrying capacity, and is more compatible with naturally occurring or laboratory-generated conditions.
Separation Between Food Species Facilitates the Observation of Autocatalytic Dynamics in the Laboratory.
[0055] Although the acceleration of a reaction over time is neither sufficient nor necessary for autocatalysis, it is a phenomenon that is most easily measured in experimental protocols. Another method of observing autocatalysis is to check whether a tiny amount of candidate autocatalysts can be used as a seed to trigger a reaction system that produces much more autocatalysts. A CompAC is more likely to exhibit reaction acceleration or seed-dependence when direct reactions between the complementary reductive and oxidative food of the comproportionation and auxiliary steps are suppressed. Based on the CompACs documented herein, there are generally three ways to suppress the direct reaction between oxidative food and reductive food: kinetic, spatial, and temporal separations.
[0056] As illustrated in
##STR00004##
[0057] Here, HNO.sub.2 and NO.sub.2 catalyze the formation of themselves through these two fast reactions, and this pathway is thus autocatalytic. Now consider another metal Z in the mixture that directly and quickly reacts with nitric acid; even if Z can be dissolved through the autocatalysis of NO.sub.2 and HNO.sub.2, the autocatalytic dynamics may be obscured. In this case, slowing the reaction between the oxidative food, HNO.sub.3, and the reductive food, metal and H.sup.+, is important for observing autocatalytic dynamics; the food species are kinetically separated as a consequence of the dramatic differences between the rate constants involved.
[0058] Spatial separation may also be used to limit the interaction between oxidative food and reductive food. For example, consider the comproportionation direction of the Boudouard reaction, possible under high temperatures:
##STR00005##
[0059] To form a CompAC as described herein, this reaction is coupled with the oxidation of CO by I.sub.2O.sub.5 under room temperature:
##STR00006##
where the autocatalysts CO.sub.2 and CO consume C and I.sub.2O.sub.5 as food, generating I.sub.2 as waste. This CompAC may be difficult to observe experimentally if one simply mixes the food species C and I.sub.2O.sub.5 together in a heated reactor region. This is because I.sub.2O.sub.5 will directly decompose to I.sub.2 and O.sub.2 and/or react with C at temperatures much lower than the desired temperature of CO.sub.2+C.fwdarw.2CO. This competing reaction may obscure the autocatalytic dynamics.
[0060] Therefore, one way to experimentally confirm autocatalysis for this this CompAC is to place I.sub.2O.sub.5 and C, which are solids, in two separate reactor regions (a comproportionation reactor region and an auxiliary reactor region) connected by two tunnels configured to only allow the diffusion of gaseous molecules. (See
[0061] Compared to kinetic separation, spatial separation is useful to not only inhibit direct and rapid reactions between food species, but also to organize reactions that require very different conditions into an autocatalytic cycle. In abiotic environments, spatial separation may occur in multiple forms. For example, if an autocatalytic cycle needs food from hydrothermal vents and the atmosphere, the food species can be separated by the body of water above the vents; if the food species are from different minerals, they can be separated by geographical barriers, such as mountains and rivers, or by simple spacing between different rocks or ores.
[0062] If the physicochemical conditions are insufficient to afford effective kinetic or spatial separation, then temporal separation between food species may also be used. For example, consider the CompAC:
##STR00007##
where the autocatalysts SO.sub.2 and S consume H.sub.2S and O.sub.2, generating H.sub.2O as a waste product. Autocatalysis in this CompAC may be experimentally confirmed using the chemical reactor system shown in
[0063] Under these periodically changing environmental conditions, wherein the food species H.sub.2S and O.sub.2 are provided at different, non-overlapping time intervals (i.e., temporally separated), the observation of autocatalytic amplification of SO.sub.2 and S may be achieved. In a natural environment, temporal separation may appear in multiple forms, such as intermittent raining, tidal cycles, geyser eruptions, a diurnal cycle, or secondary weathering or runoff patterns that lead to chemical oscillations.
[0064] As a basis for comparison, each of these three types of separation is utilized in essential ways by living organisms. For example, CO.sub.2 and H.sub.2O are kinetically separated during photosynthesis; otherwise, CO.sub.2 and H.sub.2O will spontaneously react to produce monosaccharides under sunlight. Intracellular compartments (e.g., the nucleus or the mitochondria in eukaryotes) or macromolecular centralization of multifaceted processes (e.g., ribosomal subunit interactions) can provide a microscopic structural basis of spatial separation. Temporal separation can be mediated by vegetative growth and reproductive growth. One underexplored implication for prebiotic chemistry is that a stoichiometric capability for abiotic autocatalysis may be relatively common across elements, but circumstances facilitating effective separation of key food species and reactions may be a more substantial bottleneck to actualizing autocatalytic dynamics under most cosmochemical and geochemical conditions.
[0065] Implications for Biosignature Interpretation. One of the most challenging aspects of assessing the existence of life beyond Earth is the possibility that chemical conditions on remotely sensed bodies may generate complex variations that resemble biotic influence. Autocatalytic cycles in general, and key reactions that compose CompACs in particular, may present significant challenges to biosignature characterization under conditions of pressure, temperature, and energy input that exoplanets can facilitate. The collated list of CompACs provided herein serves as a useful compendium for alternative chemical systems to be compared to remote sensing data in the event that anomalous compositions or redox disequilibria are detected.
[0066] Another question relevant to both biosignature characterization and evolutionary biology is the extent to which bioessential inorganic cofactors are utilized as a result of selection among many possible options, or whether they are more likely to be imprinted upon biology through a broader planetary or physicochemical context. Recent studies of reconstructed ancestral metal cofactor binding sites have provided reasonable cause for scrutinizing facile assumptions that link biological utilization to general environmental abundance. Responsive chemical dynamics afforded by autocatalysis are potentially impactful to biochemistry whether incorporated within the cell or mediated through external interactions. One intriguing possibility is that the same basic properties of the redox-active class of metal cofactors (e.g. iron, copper, manganese, molybdenum, etc.) that can support complex comproportionation-driven chemical dynamics are, in parallel, coincident with their propensity for biological utilization. In this view, organic chemistry may open novel possibilities for chemical separation (kinetic, temporal, or spatial) that lack geochemical counterparts. To better assess which chemical species played more critical roles during the origins or early evolution of life, theoretical analyses based on principles of chemistry and empirical data obtained by geochemical studies can be leveraged. For example, one may test whether an element with more oxidation states and a Frost diagram where the curve is generally more concave up is more likely to underlie complex dynamics based on CompACs, and then to test these attributes against the probability of biological uptake.
CONCLUSIONS
[0067] This Example has demonstrated that abiotic autocatalytic reaction systems underpinned by comproportionation (i.e., CompACs) are more frequent than previously known and notably, that the presence of CompACs is not restricted to a specific part of the periodic table. This Example shows that CompACs and their networks are likely a general phenomenon rather than a collection of special cases.
[0068] In addition to the CompACs and their networks having use in applications such as chemical manufacturing, the collated CompACs establish a starting point for a systematic assessment of the conditions under which complicated dynamics afforded by autocatalysis can occur in geochemical or cosmochemical settings that are relevant to the search for life in the universe. Such a systematic assessment may be necessary for pushing forward the understanding of abiogenesis, for disentangling false positive biosignatures from bona fide ones, and for circumscribing conditions suitable for the organization of complex chemical systems in general.
TABLE-US-00002 TABLE 2 Extended List of Comproportionation-based Autocatalytic Cycles. Serial Elements Reactions 1 .sub.1H SiHCl.sub.3 + HCl .fwdarw. SiCl.sub.4 + H.sub.2 Group 1 H.sub.2 + Cl.sub.2 .fwdarw. 2 HCl 2 .sub.1H NaH + HCl .fwdarw. NaCl + H.sub.2 Group 1 H.sub.2 + Cl.sub.2 .fwdarw. 2 HCl 3 .sub.1H NaH + HCl .fwdarw. NaCl + H.sub.2 Group 1 2 CuCl + H.sub.2 .fwdarw. 2 Cu + 2 HCl 4 .sub.1H NaH + H.sub.2O .fwdarw. NaOH + H.sub.2 Group 1 H.sub.2 + 2 Na .fwdarw. 2 NaH 5 .sub.1H 2 H.sub.2O + NaBH.sub.4 .fwdarw. 4 H.sub.2 + NaBO.sub.2 Group 1 H.sub.2 + CuO .fwdarw. H.sub.2O + Cu 6 .sub.1H 2 1/3H.sub.2O + NaBH.sub.4 .fwdarw. 4 H.sub.2 + NaBO.sub.2H.sub.2O Group 1 H.sub.2 + CuO .fwdarw. H.sub.2O + Cu 7 .sub.1H 2 HCl + 2 NaBH.sub.4 .fwdarw. 2 NaCl + B.sub.2H.sub.6 + 2 H.sub.2 Group 1 H.sub.2 + 2 FeCl.sub.3 .fwdarw. 2 HCl + 2 FeCl.sub.2 8 .sub.1H 2 HCl + 2 NaBH.sub.4 .fwdarw. 2 NaCl + B.sub.2H.sub.6 + 2 H.sub.2 Group 1 4 H.sub.2 + 2 ZrCl.sub.4 + N.sub.2 .fwdarw. 8 HCl + 2 ZrN 9 .sub.20Ca Ca + CaF.sub.2 .fwdarw. 2 CaF Group 2 3 CaF + Sc .fwdarw. 3 Ca + ScF.sub.3 10 .sub.56Ba BaCl.sub.2 + Ba .fwdarw. 2 BaCl Group 2 2 BaCl + 2 H.sub.2O .fwdarw. BaCl.sub.2 + Ba(OH).sub.2 + H.sub.2 Ba(OH).sub.2 + 2 HCl .fwdarw. BaCl.sub.2 + 2 H.sub.2O 11 .sub.57La 2 LaI.sub.3 + La .fwdarw. 3 LaI.sub.2 Ln LaI.sub.2 + ThI.sub.4 .fwdarw. LaI.sub.3 + ThI.sub.3 12 .sub.63Eu 2 EuCl.sub.3 + Eu .fwdarw. 3 EuCl.sub.2 Ln 2 EuCl.sub.2 + Cl.sub.2 .fwdarw. 2 EuCl.sub.3 13 .sub.63Eu Eu.sub.2O.sub.3 + Eu .fwdarw. 3 EuO Ln 6 EuO + O.sub.2 .fwdarw. 2 Eu.sub.3O.sub.4 4 Eu.sub.3O.sub.4 + O.sub.2 .fwdarw. 6 Eu.sub.2O.sub.3 14 .sub.90Th ThO.sub.2 + Th .fwdarw. 2 ThO An ThO + Si .fwdarw. Th + SiO 15 .sub.90Th ThI.sub.4 + ThI.sub.2 .fwdarw. 2 ThI.sub.3 An 4 ThI.sub.3 .fwdarw. Th + 3 ThI.sub.4 16 .sub.90Th ThI.sub.4 + Th .fwdarw. 2 ThI.sub.2 An ThI.sub.2 + UI.sub.4 .fwdarw. ThI.sub.3 + UI.sub.3 4 ThI.sub.3 .fwdarw. Th + 3 ThI.sub.4 17 .sub.90Th 3 ThI.sub.4 + Th .fwdarw. 4 ThI.sub.3 An 2 ThI.sub.3 .fwdarw. ThI.sub.2 + ThI.sub.4 ThI.sub.2 + UI.sub.4 .fwdarw. ThI.sub.3 + UI.sub.3 18 .sub.92U 3 UF.sub.4 + U .fwdarw. 4 UF.sub.3 An UF.sub.3 + CaF .fwdarw. UF.sub.4 + Ca 19 .sub.21Sc 2 ScCl.sub.3 + Sc.sub.5Cl.sub.8 .fwdarw. 7 ScCl.sub.2 Group 3 3 ScCl.sub.2 .fwdarw. 2 ScCl.sub.3 + Sc 20 .sub.39Y 2 YF.sub.3 + Y .fwdarw. 3 YF.sub.2 Group 3 YF.sub.2 + CaF .fwdarw. YF.sub.3 + Ca 21 .sub.22Ti Ti + 3 TiBr.sub.4 .fwdarw. 4 TiBr.sub.3 Group 4 2 TiBr.sub.3 + 2 HBr .fwdarw. 2 TiBr.sub.4 + H.sub.2 22 .sub.22Ti TiBr.sub.2 + TiBr.sub.4 .fwdarw. 2 TiBr.sub.3 Group 4 2 TiBr.sub.3 + 2 HBr .fwdarw. 2 TiBr.sub.4 + H.sub.2 23 .sub.40Zr 3 ZrCl.sub.4 + Zr .fwdarw. 4 ZrCl.sub.3 Group 4 2 ZrCl.sub.3 + 2 HCl .fwdarw. 2 ZrCl.sub.4 + H.sub.2 24 .sub.40Zr ZrI.sub.4 + ZrI.sub.2 .fwdarw. 2 ZrI.sub.3 Group 4 4 ZrI.sub.3 .fwdarw. 3 ZrI.sub.4 + Zr 25 .sub.23V V.sub.2O.sub.3 + V .fwdarw. 3 VO Group 5 4 VO + O.sub.2 .fwdarw. 2 V.sub.2O.sub.3 26 .sub.23V V.sub.2O.sub.5 + V.sub.2O.sub.3 .fwdarw. 4 VO.sub.2 Group 5 4 VO.sub.2 + O.sub.2 .fwdarw. 2 V.sub.2O.sub.5 27 .sub.23V V.sub.2O.sub.5 + V.sub.2O.sub.3 .fwdarw. 4 VO.sub.2 Group 5 2 VO.sub.2 + H.sub.2 .fwdarw. V.sub.2O.sub.3 + H.sub.2O 28 .sub.23V V.sub.2O.sub.5 + V.sub.2O.sub.3 .fwdarw. 4 VO.sub.2 Group 5 2 VO.sub.2 + CO .fwdarw. V.sub.2O.sub.3 + CO.sub.2 29 .sub.23V 2 VCl.sub.3 + V .fwdarw. 3 VCl.sub.2 Group 5 2 VCl.sub.2 + 2 HCl .fwdarw. 2 VCl.sub.3 + H.sub.2 30 .sub.23V 2 VCl.sub.3 + V .fwdarw. 3 VCl.sub.2 Group 5 VCl.sub.2 + H.sub.2 .fwdarw. V + 2 HCl 31 .sub.23V 3 VCl.sub.4 + V .fwdarw. 4 VCl.sub.3 Group 5 2 VCl.sub.3 + Cl.sub.2 .fwdarw. 2 VCl.sub.4 32 .sub.23V 3 VCl.sub.4 + V .fwdarw. 4 VCl.sub.3 Group 5 2 VCl.sub.3 + 3 H.sub.2 .fwdarw. 2 V + 6 HCl 33 .sub.23V 2 V.sup.3+ + V .fwdarw. 3 V.sup.2+ Group 5 2 V.sup.2+ + H.sub.2O.sub.2 + 2 H.sup.+ .fwdarw. 2 V.sup.3+ + 2 H.sub.2O 34 .sub.41Nb 2 NbCl.sub.3 + Nb .fwdarw. 3 NbCl.sub.2 Group 5 NbCl.sub.2 + H.sub.2 .fwdarw. Nb + 2 HCl 35 .sub.41Nb 3 NbCl.sub.5 + 2 Nb .fwdarw. 5 NbCl.sub.3 Group 5 2 NbCl.sub.3 + 3 H.sub.2 .fwdarw. 2 Nb + 6 HCl 36 .sub.41Nb 4 NbCl.sub.5 + Nb .fwdarw. 5 NbCl.sub.4 Group 5 2 NbCl.sub.4 + Cl.sub.2 .fwdarw. 2 NbCl.sub.5 37 .sub.41Nb 4 NbCl.sub.5 + Nb .fwdarw. 5 NbCl.sub.4 Group 5 2 NbCl.sub.4 + 2 CCl.sub.4 .fwdarw. 2 NbCl.sub.5 + C.sub.2Cl.sub.6 38 .sub.41Nb 2 Nb.sub.2O.sub.5 + Nb .fwdarw. 5 NbO.sub.2 Group 5 4 NbO.sub.2 + O.sub.2 .fwdarw. 2 Nb.sub.2O.sub.5 39 .sub.41Nb Nb.sub.2O.sub.5 + 3 Nb .fwdarw. 5 NbO Group 5 4 NbO + 3 O.sub.2 .fwdarw. 2 Nb.sub.2O.sub.5 40 .sub.41Nb NbO.sub.2 + Nb .fwdarw. 2 NbO Group 5 3 NbO + CO .fwdarw. 2 NbO.sub.2 + NbC 41 .sub.73Ta 4 TaCl.sub.5 + Ta .fwdarw. 5 TaCl.sub.4 Group 5 TaCl.sub.4 + NbCl.sub.5 .fwdarw. NbCl.sub.4 + TaCl.sub.5 42 .sub.73Ta TaCl.sub.5 + TaCl.sub.3 .fwdarw. 2 TaCl.sub.4 Group 5 TaCl.sub.4 + NbCl.sub.5 .fwdarw. NbCl.sub.4 + TaCl.sub.5 43 .sub.24Cr Cr.sub.2O.sub.7.sup.2 + 6 Cr.sup.2+ + 14 H.sup.+ .fwdarw. 8 Cr.sup.3+ + 7 H.sub.2O Group 6 2 Cr.sup.3+ + 3 MnO.sub.2 + 2 H.sub.2O .fwdarw. 2 HCrO.sub.4.sup. + 3 Mn.sup.2+ + 2 H.sup.+ 2 HCrO.sub.4.sup. .fwdarw. Cr.sub.2O.sub.7.sup.2 + H.sub.2O 44 .sub.24Cr 2 CrCl.sub.3 + Cr .fwdarw. 3 CrCl.sub.2 Group 6 2 CrCl.sub.2 + 2 HCl .fwdarw. 2 CrCl.sub.3 + H.sub.2 45 .sub.24Cr 2 CrCl.sub.3 + Cr .fwdarw. 3 CrCl.sub.2 Group 6 2 CrCl.sub.2 + Cl.sub.2 .fwdarw. 2 CrCl.sub.3 46 .sub.24Cr CrCl.sub.2 + CrCl.sub.4 .fwdarw. 2 CrCl.sub.3 Group 6 2 CrCl.sub.3 + Cl.sub.2 .fwdarw. 2 CrCl.sub.4 47 .sub.24Cr CrCl.sub.2 + CrCl.sub.4 .fwdarw. 2 CrCl.sub.3 Group 6 2 CrCl.sub.3 .fwdarw. 2 CrCl.sub.2 + Cl.sub.2 48 .sub.42Mo Mo.sub.2(HPO.sub.4).sub.4.sup.4 + Mo.sub.2(HPO.sub.4).sub.4.sup.2 .fwdarw. 2 Mo.sub.2(HPO.sub.4).sub.4.sup.3 Group 6 2 Mo.sub.2(HPO.sub.4).sub.4.sup.3 + 2 H.sup.+ .fwdarw. 2 Mo.sub.2(HPO.sub.4).sub.4.sup.2 + H.sub.2 49 .sub.42Mo MoCl.sub.3 + MoCl.sub.5 .fwdarw. 2 MoCl.sub.4 Group 6 2 MoCl.sub.4 .fwdarw. 2 MoCl.sub.3 + Cl.sub.2 50 .sub.42Mo MoBr.sub.2 + MoBr.sub.4 .fwdarw. 2 MoBr.sub.3 Group 6 2 MoBr.sub.3 .fwdarw. 2 MoBr.sub.2 + Br.sub.2 51 .sub.74W 2 WCl.sub.6 + W(CO).sub.6 .fwdarw. 3 WCl.sub.4 + 6 CO Group 6 WCl.sub.4 + Cl.sub.2 .fwdarw. WCl.sub.6 52 .sub.74W 2 WCl.sub.6 + W(CO).sub.6 .fwdarw. 3 WCl.sub.4 + 6 CO Group 6 WCl.sub.4 + 2 H.sub.2S .fwdarw. WS.sub.2 + 4 HCl WS.sub.2 + 3 Cl.sub.2 .fwdarw. WCl.sub.6 + S.sub.2 53 .sub.74W 49 WO.sub.3 + 5 W .fwdarw. 3 W.sub.18O.sub.49 Group 6 2 W.sub.18O.sub.49 + 5 O.sub.2 .fwdarw. 36 WO.sub.3 54 .sub.25Mn 2 KMnO.sub.4 + 3 MnSO.sub.4 + 2 H.sub.2O .fwdarw. 5 MnO.sub.2 + K.sub.2SO.sub.4 + 2 H.sub.2SO.sub.4 Group 7 2 MnO.sub.2 + 2 H.sub.2SO.sub.4 .fwdarw. 2 MnSO.sub.4 + O.sub.2 + 2 H.sub.2O 55 .sub.25Mn 2 MnO.sub.4.sup. + 3 Mn.sup.2+ + 2 H.sub.2O .fwdarw. 5 MnO.sub.2 + 4 H.sup.+ Group 7 MnO.sub.2 + 2 Fe.sup.2+ + 4 H.sup.+ .fwdarw. Mn.sup.2+ + 2 Fe.sup.3+ + 2 H.sub.2O 56 .sub.25Mn 2 KMnO.sub.4 + 3 MnSO.sub.4 + 8 H.sub.2SO.sub.4 .fwdarw. 5 Mn(SO.sub.4).sub.2 + K.sub.2SO.sub.4 + 8 H.sub.2O Group 7 Mn(SO.sub.4).sub.2 + 2 KI .fwdarw. MnSO.sub.4 + K.sub.2SO.sub.4 + I.sub.2 57 .sub.25Mn 2 MnO.sub.4.sup. + 3 Mn.sup.2+ + 7 H.sub.2O .fwdarw. 5 MnO(OH).sub.2 + 4 H.sup.+ Group 7 2 MnO(OH).sub.2 + 10 H.sup.+ + 3 BiO.sub.3.sup. .fwdarw. 2 MnO.sub.4.sup. + 3 Bi.sup.3+ + 7 H.sub.2O 58 .sub.25Mn 2 KMnO.sub.4 + MnO.sub.2 + 4 KOH .fwdarw. 3 K.sub.2MnO.sub.4 + 2 H.sub.2O Group 7 2 K.sub.2MnO.sub.4 + Cl.sub.2 .fwdarw. 2 KMnO.sub.4 + 2 KCl 59 .sub.25Mn 2 KMnO.sub.4 + MnO.sub.2 + 4 KOH .fwdarw. 3 K.sub.2MnO.sub.4 + 2 H.sub.2O Group 7 K.sub.2MnO.sub.4 + Cl.sub.2 .fwdarw. MnO.sub.2 + 2 KCl + O.sub.2 60 .sub.25Mn K.sub.2MnO.sub.4 + MnSO.sub.4 .fwdarw. 2 MnO.sub.2 + K.sub.2SO.sub.4 Group 7 MnO.sub.2 + H.sub.2SO.sub.3 .fwdarw. MnSO.sub.4 + H.sub.2O 61 .sub.25Mn K.sub.2MnO.sub.4 + MnSO.sub.4 .fwdarw. 2 MnO.sub.2 + K.sub.2SO.sub.4 Group 7 3 MnO.sub.2 + KClO.sub.3 + 3 K.sub.2CO.sub.3 .fwdarw. 3 K.sub.2MnO.sub.4 + KCl + 3 CO.sub.2 62 .sub.25Mn MnO.sub.4.sup.2 + Mn.sup.2+ .fwdarw. 2 MnO.sub.2 Group 7 MnO.sub.2 + BiO.sub.3.sup. + H.sub.2O .fwdarw. MnO.sub.4.sup.2 + Bi.sup.3+ + 2 OH.sup. 63 .sub.25Mn MnO.sub.4.sup.3 + MnO.sup.4 .fwdarw. 2 MnO.sub.4.sup.2 Group 7 2 MnO.sub.4.sup.2 + HCOO.sup. + OH.sup. .fwdarw. 2 MnO.sub.4.sup.3 + H.sub.2O + CO.sub.2 64 .sub.25Mn MnO.sub.4.sup.3 + MnO.sub.4.sup. .fwdarw. 2 MnO.sub.4.sup.2 Group 7 MnO.sub.4.sup.2 + MnO.sub.2 + 4 OH.sup. .fwdarw. 2 MnO.sub.4.sup.3 + 2 H.sub.2O 65 .sub.25Mn MnO.sub.4.sup.3 + MnO.sub.4.sup. .fwdarw. 2 MnO.sub.4.sup.2 Group 7 2 MnO.sub.4.sup.2 + SO.sub.3.sup.2 + 2 OH.sup. .fwdarw. 2 MnO.sub.4.sup.3 + SO.sub.4.sup.2 + H.sub.2O 66 .sub.25Mn MnSO.sub.4 + Mn(SO.sub.4).sub.2 .fwdarw. Mn.sub.2(SO.sub.4).sub.3 Group 7 Mn.sub.2(SO.sub.4).sub.3 + HOOCCOOH .fwdarw. 2 MnSO.sub.4 + H.sub.2SO.sub.4 + 2 CO.sub.2 67 .sub.25Mn Mn(OH).sub.2 + H.sub.2MnO.sub.3 .fwdarw. Mn.sub.2O.sub.3 + 2 H.sub.2O Group 7 2 Mn.sub.2O.sub.3 + 4 H.sub.2SO.sub.4 .fwdarw. 4 MnSO.sub.4 + O.sub.2 + 4 H.sub.2O MnSO.sub.4 + 2 NH.sub.3H.sub.2O .fwdarw. Mn(OH).sub.2 + (NH.sub.4).sub.2SO.sub.4 68 .sub.25Mn MnO.sub.2 + 2 Mn(OH).sub.2 .fwdarw. Mn.sub.3O.sub.4 + 2 H.sub.2O Group 7 4 Mn.sub.3O.sub.4 + O.sub.2 .fwdarw. 6 Mn.sub.2O.sub.3 2 Mn.sub.2O.sub.3 + O.sub.2 .fwdarw. 4 MnO.sub.2 69 .sub.75Re 3 Re.sub.2O.sub.7 + Re .fwdarw. 7 ReO.sub.3 Group 7 4 ReO.sub.3 + O.sub.2 .fwdarw. 2 Re.sub.2O.sub.7 70 .sub.75Re 2 Re.sub.2O.sub.7 + 3 Re .fwdarw. 7 ReO.sub.2 Group 7 4 ReO.sub.2 + 3 O.sub.2 .fwdarw. 2 Re.sub.2O.sub.7 71 .sub.75Re Re.sub.2O.sub.7 + ReO.sub.2 .fwdarw. 3 ReO.sub.3 Group 7 4 ReO.sub.3 + O.sub.2 .fwdarw. 2 Re.sub.2O.sub.7 72 .sub.75Re 3 Re.sub.2O.sub.7 + Re .fwdarw. 7 ReO.sub.3 Group 7 ReO.sub.3 + 3 H.sub.2 .fwdarw. Re + 3 H.sub.2O 73 .sub.75Re Re + 2 ReO.sub.3 .fwdarw. 3 ReO.sub.2 Group 7 Re.sub.2O.sub.7 + ReO.sub.2 .fwdarw. 3 ReO.sub.3 74 .sub.75Re 2 ReF.sub.6 + Re .fwdarw. 3 ReF.sub.4 Group 7 ReF.sub.4 .fwdarw. Re + 2 F.sub.2 75 .sub.26Fe Fe + 2 Fe.sup.3+ .fwdarw. 3 Fe.sup.2+ Group 8 2 Fe.sup.2+ + Cl.sub.2 .fwdarw. 2 Fe.sup.3+ + 2 Cl.sup. 76 .sub.26Fe Fe + 2 Fe.sup.3+ .fwdarw. 3 Fe.sup.2+ Group 8 Fe.sup.2+ + Zn .fwdarw. Fe + Zn.sup.2+ 77 .sub.26Fe Fe + 2 Fe.sup.3+ .fwdarw. 3 Fe.sup.2+ Group 8 Fe.sup.2+ + CO.sub.3.sup.2 .fwdarw. FeCO.sub.3 FeCO.sub.3 .fwdarw. FeO + CO.sub.2 FeO + CO .fwdarw. Fe + CO.sub.2 78 .sub.26Fe Fe.sub.2O.sub.3 + Fe .fwdarw. 3 FeO Group 8 4 FeO + O.sub.2 .fwdarw. 2 Fe.sub.2O.sub.3 79 .sub.26Fe Fe.sub.2O.sub.3 + Fe .fwdarw. 3 FeO Group 8 FeO + CO .fwdarw. Fe + CO.sub.2 80 .sub.27Co CoSi.sub.2 + Co .fwdarw. 2 CoSi Group 9 CoSi + Si .fwdarw. CoSi.sub.2 81 .sub.27Co CoSi.sub.2 + Co.sub.2Si .fwdarw. 3 CoSi Group 9 CoSi + Si .fwdarw. CoSi.sub.2 82 .sub.27Co CoSi.sub.2 + Co.sub.2Si .fwdarw. 3 CoSi Group 9 CoSi + Co .fwdarw. Co.sub.2Si 83 .sub.27Co Co.sub.3O.sub.4 + Co .fwdarw. 4 CoO Group 9 CoO + CO .fwdarw. Co + CO.sub.2 84 .sub.27Co Co.sub.3O.sub.4 + Co .fwdarw. 4 CoO Group 9 6 CoO + O.sub.2 .fwdarw. 2 Co.sub.3O.sub.4 85 .sub.27Co Co + 2 Co(OH).sub.3 + 6 CH.sub.3COOH + 6 H.sub.2O .fwdarw. 3 Group 9 Co(CH.sub.3COO).sub.24H.sub.2O Co(CH.sub.3COO).sub.24H.sub.2O .fwdarw. Co.sup.2+ + 2 CH.sub.3COO.sup. + 4 H.sub.2O Co.sup.2+ + 2 BH.sub.4.sup. + 6 H.sub.2O .fwdarw. Co + 2 B(OH).sub.3 + 7 H.sub.2 86 .sub.28Ni NiO.sub.2 + Ni(OH).sub.2 .fwdarw. 2 NiOOH Group 10 2 NiOOH + Fe + 2 H.sub.2O .fwdarw. Fe(OH).sub.2 + 2 Ni(OH).sub.2 87 .sub.28Ni NiSi.sub.2 + Ni.sub.2Si .fwdarw. 3 NiSi Group 10 NiSi + Si .fwdarw. NiSi.sub.2 88 .sub.28Ni NiS.sub.2 + Ni.sub.3S.sub.2 .fwdarw. 4 NiS Group 10 NiS + H.sub.2S .fwdarw. NiS.sub.2 + H.sub.2 89 .sub.28Ni NiS.sub.2 + Ni.sub.3S.sub.2 .fwdarw. 4 NiS Group 10 3 NiS + H.sub.2 .fwdarw. Ni.sub.3S.sub.2 + H.sub.2S 90 .sub.28Ni Ni + Ni.sub.2O.sub.3 .fwdarw. 3 NiO Group 10 NiO + CO .fwdarw. Ni + CO.sub.2 91 .sub.28Ni Ni + Ni.sub.2O.sub.3 .fwdarw. 3 NiO Group 10 4 NiO + O.sub.2 .fwdarw. 2 Ni.sub.2O.sub.3 92 .sub.28Ni Ni + 2 Ni(OH).sub.3 + 6 CH.sub.3COOH + 6 H.sub.2O .fwdarw. 3 Ni(CH.sub.3COO).sub.24H.sub.2O Group 10 Ni(CH.sub.3COO).sub.24H.sub.2O .fwdarw. 0.86Ni(CH.sub.3COO).sub.20.14Ni(OH).sub.2 + 0.28 CH.sub.3COOH + 3.72 H.sub.2O 0.86Ni(CH.sub.3COO).sub.20.14Ni(OH).sub.2 .fwdarw. NiO + 0.86 CH.sub.3COCH.sub.3 + 0.86 CO.sub.2 + 0.14 H.sub.2O NiO + H.sub.2 .fwdarw. Ni + H.sub.2O 93 .sub.29Cu Cu + Cu.sup.2+ .fwdarw. 2 Cu.sup.+ Group 11 Cu.sup.+ + Fe.sup.3+ .fwdarw. Cu.sup.2+ + Fe.sup.2+ 94 .sub.29Cu Cu + CuCl.sub.2 .fwdarw. 2 CuCl Group 11 2 CuCl + H.sub.2 .fwdarw. 2 Cu + 2 HCl 95 .sub.29Cu Cu + CuO .fwdarw. Cu.sub.2O Group 11 Cu.sub.2O + H.sub.2 .fwdarw. 2 Cu + H.sub.2O 96 .sub.47Ag Ag.sup.2+ + Ag .fwdarw. 2 Ag.sup.+ Group 11 2 Ag.sup.+ + S.sub.2O.sub.8.sup.2 .fwdarw. 2 Ag.sup.2+ + 2 SO.sub.4.sup.2 97 .sub.47Ag Ag.sup.2+ + Ag .fwdarw. 2 Ag.sup.+ Group 11 Ag.sup.+ + Cl.sup. .fwdarw. AgCl 2 AgCl + H.sub.2 .fwdarw. 2 Ag + 2 HCl 98 .sub.47Ag AgF + KAgF.sub.4 .fwdarw. 2 AgF.sub.2 + KF Group 11 2 AgF.sub.2 + 2 KF + F.sub.2 .fwdarw. 2 KAgF.sub.4 99 .sub.47Ag AgF + KAgF.sub.4 .fwdarw. 2 AgF.sub.2 + KF Group 11 2 AgF.sub.2 .fwdarw. 2 AgF + F.sub.2 100 .sub.79Au AuCl.sub.3 + 2 Au .fwdarw. 3 AuCl Group 11 2 AuCl .fwdarw. 2 Au + Cl.sub.2 101 .sub.79Au AuCl.sub.3 + 2 Au .fwdarw. 3 AuCl Group 11 AuCl + Cl.sub.2 .fwdarw. AuCl.sub.3 102 .sub.48Cd Cd + CdSO.sub.4 .fwdarw. Cd.sub.2SO.sub.4 Group 12 3 Cd.sub.2SO.sub.4 + 2 HNO.sub.3 + 3 H.sub.2SO.sub.4 .fwdarw. 6 CdSO.sub.4 + 2 NO + 4 H.sub.2O 103 .sub.80Hg Hg + Hg.sup.2+ .fwdarw. Hg.sub.2.sup.2+ Group 12 Hg.sub.2.sup.2+ + 2 Fe.sup.2+ .fwdarw. 2 Hg + 2 Fe.sup.3+ 104 .sub.80Hg Hg + Hg.sup.2+ .fwdarw. Hg.sub.2.sup.2+ Group 12 Hg.sub.2.sup.2+ + H.sub.2 .fwdarw. 2 Hg + 2 H.sup.+ 105 .sub.80Hg Hg + Hg.sup.2+ .fwdarw. Hg.sub.2.sup.2+ Group 12 Hg.sub.2.sup.2+ + 2 Co.sup.3+ .fwdarw. 2 Hg.sup.2+ + 2 Co.sup.2+ 106 .sub.80Hg Hg + Hg.sup.2+ .fwdarw. Hg.sub.2.sup.2+ Group 12 Hg.sub.2.sup.2+ + S.sub.2O.sub.8.sup.2 .fwdarw. 2 Hg.sup.2+ + 2 SO.sub.4.sup.2 107 .sub.80Hg Hg + HgCl.sub.2 .fwdarw. Hg.sub.2Cl.sub.2 Group 12 Hg.sub.2Cl.sub.2 + Fe .fwdarw. 2 Hg + FeCl.sub.2 108 .sub.80Hg Hg + HgCl.sub.2 .fwdarw. Hg.sub.2Cl.sub.2 Group 12 Hg.sub.2Cl.sub.2 + Cl.sub.2 .fwdarw. 2 HgCl.sub.2 109 .sub.5B 2 B.sub.2O.sub.3 + 2 B .fwdarw. 3 B.sub.2O.sub.2 Group 13 B.sub.2O.sub.2 + 2 NH.sub.3 .fwdarw. 2 BN + 2 H.sub.2O + H.sub.2 2 BN + 3 H.sub.2O .fwdarw. B.sub.2O.sub.3 + 2 NH.sub.3 110 .sub.5B 2 B.sub.2O.sub.3 + 2 B .fwdarw. 3 B.sub.2O.sub.2 Group 13 B.sub.2O.sub.2 + 2 H.sub.2 .fwdarw. 2 B + 2 H.sub.2O 111 .sub.5B 7 B.sub.2O.sub.3 + 2 TiB.sub.2 .fwdarw. 9 B.sub.2O.sub.2 + Ti.sub.2O.sub.3 Group 13 B.sub.2O.sub.2 + 2 NH.sub.3 .fwdarw. 2 BN + 2 H.sub.2O + H.sub.2 2 BN + 3 H.sub.2O .fwdarw. B.sub.2O.sub.3 + 2 NH.sub.3 112 .sub.5B 16 B + B.sub.2O.sub.3 .fwdarw. 3 B.sub.6O Group 13 9 B.sub.6O + 4 CaCO.sub.3 .fwdarw. 4 CaB.sub.6 + 4 B.sub.4C + 7 B.sub.2O.sub.3 113 .sub.5B 16 B + B.sub.2O.sub.3 .fwdarw. 3 B.sub.6O Group 13 5 B.sub.6O + 4 CaO .fwdarw. 4 CaB.sub.6 + 3 B.sub.2O.sub.3 114 .sub.5B 16 B + B.sub.2O.sub.3 .fwdarw. 3 B.sub.6O Group 13 B.sub.6O + 4 O.sub.2 .fwdarw. 3 B.sub.2O.sub.3 115 .sub.5B 16 B + B.sub.2O.sub.3 .fwdarw. 3 B.sub.6O Group 13 2 B.sub.6O .fwdarw. 10 B + B.sub.2O.sub.2 B.sub.2O.sub.2 + 2 H.sub.2 .fwdarw. 2 B + 2 H.sub.2O 116 .sub.13Al AlCl.sub.3 + 2 Al .fwdarw. 3 AlCl Group 13 AlCl + Cl.sub.2 .fwdarw. AlCl.sub.2 + Cl AlCl.sub.2 + Cl.sub.2 .fwdarw. AlCl.sub.3 + Cl 117 .sub.13Al 2 AlCl.sub.3 + Al .fwdarw. 3 AlCl.sub.2 Group 13 AlCl.sub.2 + Cl.sub.2 .fwdarw. AlCl.sub.3 + Cl 118 .sub.31Ga Ga.sub.2O.sub.3 + 4 Ga .fwdarw. 3 Ga.sub.2O Group 13 Ga.sub.2O + O.sub.2 .fwdarw. Ga.sub.2O.sub.3 119 .sub.31Ga Ga.sub.2O.sub.3 + 4 Ga .fwdarw. 3 Ga.sub.2O Group 13 Ga.sub.2O + 2 NH.sub.3 .fwdarw. 2 GaN + H.sub.2O + 2 H.sub.2 2 GaN + 3 H.sub.2 .fwdarw. 2 Ga + 2 NH.sub.3 120 .sub.31Ga 2 Ga + Ga.sub.2S.sub.2 .fwdarw. 2 Ga.sub.2S Group 13 Ga.sub.2S + H.sub.2 .fwdarw. 2 Ga + H.sub.2S 121 .sub.31Ga 2 Ga + Ga.sub.2S.sub.2 .fwdarw. 2 Ga.sub.2S Group 13 3 Ga.sub.2S + 6 HCl .fwdarw. 4 Ga + 2 GaCl.sub.3 + 3 H.sub.2S 122 .sub.31Ga Ga + 2 GaCl.sub.3 .fwdarw. 3 GaCl.sub.2 Group 13 2 GaCl.sub.2 + 2 NH.sub.3 .fwdarw. 2 GaN + 4 HCl + H.sub.2 2 GaN .fwdarw. 2 Ga + N.sub.2 123 .sub.6C C + CO.sub.2 .fwdarw. 2 CO Group 14 CO + FeO .fwdarw. Fe + CO.sub.2 124 .sub.6C C + CO.sub.2 .fwdarw. 2 CO Group 14 CO + H.sub.2 .fwdarw. H.sub.2O + C 125 .sub.6C (CN).sub.2 + 2 CO.sub.2 .fwdarw. 4 CO + N.sub.2 Group 14 CO + FeO .fwdarw. Fe + CO.sub.2 126 .sub.6C C + CO.sub.2 .fwdarw. 2 CO Group 14 5 CO + I.sub.2O.sub.5 .fwdarw. I.sub.2 + 5 CO.sub.2 127 .sub.6C CaC.sub.2 + CO .fwdarw. CaO + 3 C Group 14 C + Cl.sub.2 + H.sub.2O .fwdarw. CO + 2 HCl 128 .sub.6C 2 CaC.sub.2 + CS.sub.2 .fwdarw. 2 CaS + 5 C Group 14 C + 2S .fwdarw. CS.sub.2 129 .sub.6C 2 CaC.sub.2 + CCl.sub.4 .fwdarw. 2 CaCl.sub.2 + 5 C Group 14 C + 2 Cl.sub.2 .fwdarw. CCl.sub.4 130 .sub.6C CH.sub.4 + CO.sub.2 .fwdarw. 2 CO + 2 H.sub.2 Group 14 CO + 3 H.sub.2 .fwdarw. CH.sub.4 + H.sub.2O 131 .sub.6C CH.sub.4 + CO.sub.2 .fwdarw. 2 CO + 2 H.sub.2 Group 14 CO + FeO .fwdarw. CO.sub.2 + Fe 132 .sub.14Si SiO.sub.2 + Si .fwdarw. 2 SiO Group 14 SiO + CO .fwdarw. SiO.sub.2 + C 133 .sub.14Si SiO.sub.2 + Si .fwdarw. 2 SiO Group 14 SiO + C .fwdarw. Si + CO 134 .sub.14Si SiO.sub.2 + Si .fwdarw. 2 SiO Group 14 Mg.sub.2Si + 2 SiO .fwdarw. 3 Si + 2 MgO 135 .sub.14Si Si + 3 SiCl.sub.4 + 2 H.sub.2 .fwdarw. 4 SiHCl.sub.3 Group 14 SiHCl.sub.3 + H.sub.2 .fwdarw. Si + 3 HCl 136 .sub.14Si Si + 3 SiCl.sub.4 + 2 H.sub.2 .fwdarw. 4 SiHCl.sub.3 Group 14 SiHCl.sub.3 + Cl.sub.2 .fwdarw. SiCl.sub.4 + HCl 137 .sub.32Ge GeCl.sub.4 + Ge .fwdarw. 2 GeCl.sub.2 Group 14 GeCl.sub.2 + Cl.sub.2 .fwdarw. GeCl.sub.4 138 .sub.32Ge GeO.sub.2 + Ge .fwdarw. 2 GeO Group 14 2 GeO + O.sub.2 .fwdarw. 2 GeO.sub.2 139 .sub.50Sn Sn.sup.4+ + Sn .fwdarw. 2 Sn.sup.2+ Group 14 Sn.sup.2+ + I.sub.2 .fwdarw. 2 I.sup. + Sn.sup.4+ 140 .sub.50Sn Sn.sup.4+ + Sn .fwdarw. 2 Sn.sup.2+ Group 14 Sn.sup.2+ + Fe .fwdarw. Fe.sup.2+ + Sn 141 .sub.82Pb Pb + PbO.sub.2 + 2 H.sub.2SO.sub.4 .fwdarw. 2 PbSO.sub.4 + 2 H.sub.2O Group 14 PbSO.sub.4 + 4 CO .fwdarw. PbS + 4 CO.sub.2 PbSO.sub.4 + PbS .fwdarw. 2 Pb + 2 SO.sub.2 142 .sub.82Pb Pb + PbO.sub.2 + 2 H.sub.2SO.sub.4 .fwdarw. 2 PbSO.sub.4 + 2 H.sub.2O Group 14 PbSO.sub.4 + 2 H.sub.2 .fwdarw. Pb + SO.sub.2 + 2 H.sub.2O 143 .sub.82Pb Pb + PbO.sub.2 + 2 H.sub.2SO.sub.4 .fwdarw. 2 PbSO.sub.4 + 2 H.sub.2O Group 14 PbSO.sub.4 .fwdarw. PbO.sub.2 + SO.sub.2 144 .sub.82Pb 2 PbO + PbO.sub.2 .fwdarw. Pb.sub.3O.sub.4 Group 14 2 Pb.sub.3O.sub.4 .fwdarw. 6 PbO + O.sub.2 145 .sub.7N HNO.sub.2 + HNO.sub.3 .fwdarw. 2 NO.sub.2 + H.sub.2O Group 15 2 NO.sub.2 + Cu + 2 H.sup.+ .fwdarw. 2 HNO.sub.2 + Cu.sup.2+ 146 .sub.7N NH.sub.4NO.sub.3 .fwdarw. 2 H.sub.2O + N.sub.2O Group 15 N.sub.2O + H.sub.2SO.sub.4 .fwdarw. 2 NO + SO.sub.2 + H.sub.2O 2 NO + O.sub.2 .fwdarw. 2 NO.sub.2 4 NO.sub.2 + 2 H.sub.2O + O.sub.2 .fwdarw. 4 HNO.sub.3 HNO.sub.3 + NH.sub.3 .fwdarw. NH.sub.4NO.sub.3 147 .sub.7N 2 NH.sub.4NO.sub.3 .fwdarw. 2 N.sub.2 + O.sub.2 + 4 H.sub.2O Group 15 N.sub.2 + 3 Mg .fwdarw. Mg.sub.3N.sub.2 Mg.sub.3N.sub.2 + 6 H.sub.2O .fwdarw. 3 Mg(OH).sub.2 + 2 NH.sub.3 HNO.sub.3 + NH.sub.3 .fwdarw. NH.sub.4NO.sub.3 148 .sub.7N N.sub.2O.sub.5 + NO .fwdarw. 3 NO.sub.2 Group 15 2 NO.sub.2 .fwdarw. 2 NO + O.sub.2 149 .sub.7N N.sub.2O.sub.5 + NO .fwdarw. 3 NO.sub.2 Group 15 2 NO.sub.2 + O.sub.3 .fwdarw. N.sub.2O.sub.5 + O.sub.2 150 .sub.7N NO.sub.2 + NO .fwdarw. N.sub.2O.sub.3 Group 15 N.sub.2O.sub.3 + 2 HNO.sub.3 .fwdarw. 4 NO.sub.2 + H.sub.2O 151 .sub.7N NO.sub.2 + NO .fwdarw. N.sub.2O.sub.3 Group 15 N.sub.2O.sub.3 + 2 Hg + H.sub.2SO.sub.4 .fwdarw. 2 NO + Hg.sub.2SO.sub.4 + H.sub.2O 152 .sub.7N NH.sub.2OH + HNO.sub.2 .fwdarw. N.sub.2O + 2 H.sub.2O Group 15 N.sub.2O + H.sub.2SO.sub.4 .fwdarw. 2 NO + SO.sub.2 + H.sub.2O 2 NO + O.sub.2 .fwdarw. 2 NO.sub.2 NO.sub.2 + NO + H.sub.2O .fwdarw. 2 HNO.sub.2 153 .sub.15P 2 PH.sub.3 + 2 PCl.sub.3 .fwdarw. P.sub.4 + 6 HCl Group 15 P.sub.4 + 6 Cl.sub.2 .fwdarw. 4 PCl.sub.3 154 .sub.15P 2 PH.sub.3 + 2 PCl.sub.3 .fwdarw. P.sub.4 + 6 HCl Group 15 P.sub.4 + 6 H.sub.2 .fwdarw. 4 PH.sub.3 155 .sub.15P 2 PH.sub.3 + 2 PCl.sub.3 .fwdarw. P.sub.4 + 6 HCl Group 15 P.sub.4 + 3 O.sub.2 + 6 H.sub.2O .fwdarw. 4 H.sub.3PO.sub.3 H.sub.3PO.sub.3 + 3 Zn + 6 H.sup.+ .fwdarw. PH.sub.3 + 3 Zn.sup.2+ + 3 H.sub.2O 156 .sub.15P 2 PH.sub.3 + 2 PCl.sub.3 .fwdarw. P.sub.4 + 6 HCl Group 15 2 P.sub.4 + 3 Ba(OH).sub.2 + 6 H.sub.2O .fwdarw. 3 Ba(H.sub.2PO.sub.2).sub.2 + 2 PH.sub.3 Ba(H.sub.2PO.sub.2).sub.2 + H.sub.2SO.sub.4 .fwdarw. 2 H.sub.3PO.sub.2 + BaSO.sub.4 2 H.sub.3PO.sub.2 .fwdarw. PH.sub.3 + H.sub.3PO.sub.4 157 .sub.15P 2 PH.sub.3 + 2 PCl.sub.3 .fwdarw. P.sub.4 + 6 HCl Group 15 P.sub.4 + 4 B .fwdarw. 4 BP BP + NH.sub.3 .fwdarw. PH.sub.3 + BN 158 .sub.15P 2 PH.sub.3 + 2 PCl.sub.3 .fwdarw. P.sub.4 + 6 HCl Group 15 P.sub.4 + 4 I.sub.2 .fwdarw. 2 P.sub.2I.sub.4 13 P.sub.4 + 10 P.sub.2I.sub.4 + 128 H.sub.2O .fwdarw. 40 PH.sub.4I + 32 H.sub.3PO.sub.4 PH.sub.4I .fwdarw. PH.sub.3 + HI 159 .sub.15P PH.sub.3 + 3 PCl.sub.5 .fwdarw. 4 PCl.sub.3 + 3 HCl Group 15 PCl.sub.3 + Cl.sub.2 .fwdarw. PCl.sub.5 160 .sub.15P 3 H.sub.3PO.sub.4 + 2 P + 3 H.sub.2O .fwdarw. 5 H.sub.3PO.sub.3 Group 15 4 H.sub.3PO.sub.3 .fwdarw. 3 H.sub.3PO.sub.4 + PH.sub.3 161 .sub.15P 3 PCl.sub.5 + 3 PH.sub.4I .fwdarw. PI.sub.3 + PCl.sub.3 + P.sub.4 + 12 HCl Group 15 PCl.sub.3 + Cl.sub.2 .fwdarw. PCl.sub.5 P.sub.4 + 10 Cl.sub.2 .fwdarw. 4 PCl.sub.5 162 .sub.33As 3 H.sub.3AsO.sub.4 + 5 AsH.sub.3 .fwdarw. 8 As + 12 H.sub.2O Group 15 6 As + 5 K.sub.2Cr.sub.2O.sub.7 + 20 H.sub.2SO.sub.4 .fwdarw. 3 As.sub.2O.sub.5 + 5 Cr.sub.2(SO.sub.4).sub.3 + 5 K.sub.2SO.sub.4 + 20 H.sub.2O As.sub.2O.sub.5 + 3 H.sub.2O .fwdarw. 2 H.sub.3AsO.sub.4 163 .sub.33As 3 H.sub.3AsO.sub.4 + 5 AsH.sub.3 .fwdarw. 8 As + 12 H.sub.2O Group 15 2 As + 5 Cl.sub.2 + 8 H.sub.2O .fwdarw. 2 H.sub.3AsO.sub.4 + 10 HCl 164 .sub.33As 3 H.sub.3AsO.sub.4 + 5 AsH.sub.3 .fwdarw. 8 As + 12 H.sub.2O Group 15 2 As + 5 NaClO + 3 H.sub.2O .fwdarw. 2 H.sub.3AsO.sub.4 + 5 NaCl 165 .sub.33As 3 H.sub.3AsO.sub.4 + 5 AsH.sub.3 .fwdarw. 8 As + 12 H.sub.2O Group 15 2 As + 6 HCOONa .fwdarw. 2 AsH.sub.3 + 3 Na.sub.2C.sub.2O.sub.4 166 .sub.33As AsH.sub.3 + AsCl.sub.3 .fwdarw. 2 As + 3 HCl Group 15 2 As + 3 HgCl.sub.2 .fwdarw. 2 AsCl.sub.3 + 3 Hg 167 .sub.33As AsH.sub.3 + AsCl.sub.3 .fwdarw. 2 As + 3 HCl Group 15 2 As + 3 H.sub.2 .fwdarw. 2 AsH.sub.3 168 .sub.33As 4 AsI.sub.3 + 2 As .fwdarw. 3 As.sub.2I.sub.4 Group 15 As.sub.2I.sub.4 + I.sub.2 .fwdarw. 2 AsI.sub.3 169 .sub.33As As.sub.4 + 4 Co.sub.3As.sub.2 .fwdarw. 12 CoAs Group 15 20 CoAs .fwdarw. 3 As.sub.4 + 4 Co.sub.5As.sub.2 2 Co.sub.5As.sub.2 .fwdarw. As.sub.4 + 10 Co 170 .sub.8O O.sub.2 + 2 Na.sub.2O .fwdarw. 2 Na.sub.2O.sub.2 Group 16 Na.sub.2O.sub.2 + H.sub.2SO.sub.4 .fwdarw. H.sub.2O.sub.2 + Na.sub.2SO.sub.4 H.sub.2O.sub.2 + Cl.sub.2 .fwdarw. O.sub.2 + 2 HCl 171 .sub.8O H.sub.2O + O.sub.3 .fwdarw. 2 OH + O.sub.2 Group 16 OH + HCl .fwdarw. H.sub.2O + Cl 172 .sub.8O H.sub.2O + O.sub.3 .fwdarw. H.sub.2O.sub.2 + O.sub.2 Group 16 H.sub.2O.sub.2 + H.sub.2S .fwdarw. 2 H.sub.2O + S 173 .sub.8O H.sub.2O + O.sub.3 .fwdarw. H.sub.2O.sub.2 + O.sub.2 Group 16 H.sub.2O.sub.2 + Cl.sub.2 .fwdarw. O.sub.2 + 2 HCl 3 O.sub.2 .fwdarw. 2 O.sub.3 174 .sub.8O OF.sub.2 + H.sub.2O .fwdarw. O.sub.2 + 2 HF Group 16 O.sub.2 + 2 H.sub.2 .fwdarw. 2 H.sub.2O 175 .sub.8O 2 Na.sub.2O + O.sub.2 .fwdarw. 2 Na.sub.2O.sub.2 Group 16 Na.sub.2O.sub.2 + 2 HCl .fwdarw. 2 NaCl + H.sub.2O.sub.2 H.sub.2O.sub.2 + Cl.sub.2 .fwdarw. 2 HCl + O.sub.2 176 .sub.8O 2 Na.sub.2O + O.sub.2 .fwdarw. 2 Na.sub.2O.sub.2 Group 16 Na.sub.2O.sub.2 + 2 Na .fwdarw. 2 Na.sub.2O 177 .sub.16S 2 H.sub.2S + SO.sub.2 .fwdarw. 3 S + 2 H.sub.2O Group 16 S + H.sub.2 .fwdarw. H.sub.2S 178 .sub.16S SO.sub.2 + 2 H.sub.2S .fwdarw. 3 S + 2 H.sub.2O Group 16 S + O.sub.2 .fwdarw. SO.sub.2 179 .sub.16S Na.sub.2SO.sub.3 + S .fwdarw. Na.sub.2S.sub.2O.sub.3 Group 16 3 Na.sub.2S.sub.2O.sub.3 + 6 NaOH .fwdarw. 2 Na.sub.2S + 4 Na.sub.2SO.sub.3 + 3 H.sub.2O 180 .sub.16S Na.sub.2SO.sub.3 + S .fwdarw. Na.sub.2S.sub.2O.sub.3 Group 16 3 Na.sub.2S.sub.2O.sub.3 + 4 NaOH + 2 NaNO.sub.2 + H.sub.2O .fwdarw. 6 Na.sub.2SO.sub.3 + 2 NH.sub.3 181 .sub.16S HOSCN + SCN.sup. + H.sup.+ .fwdarw. (SCN).sub.2 + H.sub.2O Group 16 3 (SCN).sub.2 + 4 H.sub.2O .fwdarw. H.sub.2SO.sub.4 + HCN + 5 SCN.sup. + 5H.sup.+ 182 .sub.16S HOSCN + SCN.sup. + H.sup.+ .fwdarw. (SCN).sub.2 + H.sub.2O Group 16 (SCN).sub.2 + H.sub.2S .fwdarw. S + 2 SCN.sup. + 2 H.sup.+ 183 .sub.16S 2 H.sub.2SO.sub.4 + S .fwdarw. 3 SO.sub.2 + 2 H.sub.2O Group 16 2 SO.sub.2 + O.sub.2 + 2 H.sub.2O .fwdarw. 2 H.sub.2SO.sub.4 184 .sub.16S 2 H.sub.2SO.sub.4 + S .fwdarw. 3 SO.sub.2 + 2 H.sub.2O Group 16 SO.sub.2 + 2 CO .fwdarw. S + 2 CO.sub.2 185 .sub.16S CS.sub.2 + 3 SO.sub.3 .fwdarw. COS + 4 SO.sub.2 Group 16 SO.sub.2 + 3 Fe.sub.2O.sub.3 .fwdarw. SO.sub.3 + 2 Fe.sub.3O.sub.4 186 .sub.16S CS.sub.2 + 3 SO.sub.3 .fwdarw. COS + 4 SO.sub.2 Group 16 2 COS + C .fwdarw. CS.sub.2 + 2 CO 2 SO.sub.2 + 2 C .fwdarw. S.sub.2 + 2 CO.sub.2 S.sub.2 + C .fwdarw. CS.sub.2 187 .sub.16S SO.sub.2 + 3 S .fwdarw. 2 S.sub.2O Group 16 S.sub.2O + O.sub.3 .fwdarw. 2 SO.sub.2 188 .sub.34Se H.sub.2SeO.sub.3 + 2 H.sub.2Se .fwdarw. 3 Se + 3 H.sub.2O Group 16 3 Se + 4 HNO.sub.3 + H.sub.2O .fwdarw. 3 H.sub.2SeO.sub.3 + 4 NO 189 .sub.34Se H.sub.2SeO.sub.3 + 2 H.sub.2Se .fwdarw. 3 Se + 3 H.sub.2O Group 16 Se + H.sub.2 .fwdarw. H.sub.2Se 190 .sub.34Se Se + 2 H.sub.2SeO.sub.4 + H.sub.2O .fwdarw. 3 H.sub.2SeO.sub.3 Group 16 3 H.sub.2SeO.sub.3 + HClO.sub.3 .fwdarw. 3 H.sub.2SeO.sub.4 + HCl 191 .sub.34Se Se + 2 H.sub.2SeO.sub.4 + H.sub.2O .fwdarw. 3 H.sub.2SeO.sub.3 Group 16 H.sub.2SeO.sub.3 + 2 NH.sub.2OH .fwdarw. Se + N.sub.2O + 4 H.sub.2O 192 .sub.34Se Se.sub.2Cl.sub.2 + ZnSe .fwdarw. 3 Se + ZnCl.sub.2 Group 16 2 Se + Cl.sub.2 .fwdarw. Se.sub.2Cl.sub.2 193 .sub.34Se Se.sub.2Cl.sub.2 + ZnSe .fwdarw. 3 Se + ZnCl.sub.2 Group 16 Se + Zn .fwdarw. ZnSe 194 .sub.34Se 3 Se + SeCl.sub.4 .fwdarw. 2 Se.sub.2Cl.sub.2 Group 16 Se.sub.2Cl.sub.2 + 2 FeCl.sub.2 .fwdarw. 2 Se + 2 FeCl.sub.3 195 .sub.34Se 3 Se + SeCl.sub.4 .fwdarw. 2 Se.sub.2Cl.sub.2 Group 16 Se.sub.2Cl.sub.2 + 3 Cl.sub.2 .fwdarw. 2 SeCl.sub.4 196 .sub.52Te Te + TeCl.sub.4 .fwdarw. 2 TeCl.sub.2 Group 16 TeCl.sub.2 + Cl.sub.2 .fwdarw. TeCl.sub.4 197 .sub.52Te 2 H.sub.2Te + TeO.sub.2 .fwdarw. 3 Te + 2 H.sub.2O Group 16 Te + 2 H.sub.2O .fwdarw. TeO.sub.2 + 2 H.sub.2 198 .sub.52Te 2 H.sub.2Te + TeCl.sub.4 .fwdarw. 3 Te + 4 HCl Group 16 Te + 2 Cl.sub.2 .fwdarw. TeCl.sub.4 199 .sub.52Te Te + 2 TeF.sub.6 .fwdarw. 3 TeF.sub.4 Group 16 TeF.sub.4 + 2 H.sub.2S .fwdarw. Te + 4 HF + 2 S 200 .sub.52Te Te + 2 H.sub.2TeO.sub.4 + H.sub.2O .fwdarw. 3 H.sub.2TeO.sub.3 Group 16 H.sub.2TeO.sub.3 + 2 SO.sub.2 + H.sub.2O .fwdarw. Te + 2 H.sub.2SO.sub.4 201 .sub.52Te Te + 2 H.sub.2TeO.sub.4 + H.sub.2O .fwdarw. 3 H.sub.2TeO.sub.3 Group 16 3 H.sub.2TeO.sub.3 + K.sub.2Cr.sub.2O.sub.7 + 4 H.sub.2SO.sub.4 .fwdarw. 3 H.sub.2TeO.sub.4 + Cr.sub.2(SO.sub.4).sub.3 + K.sub.2SO.sub.4 + 4 H.sub.2O 202 .sub.17Cl HCl + HOCl .fwdarw. Cl.sub.2 + H.sub.2O Group 17 Cl.sub.2 + H.sub.2 .fwdarw. 2 HCl 203 .sub.17Cl HClO.sub.4 + 7 HCl .fwdarw. 4 Cl.sub.2 + 4 H.sub.2O Group 17 Cl.sub.2 + H.sub.2S .fwdarw. 2 HCl + S 204 .sub.17Cl HClO.sub.3 + 5 HCl .fwdarw. 3 Cl.sub.2 + 3 H.sub.2O Group 17 Cl.sub.2 + 2 HBr .fwdarw. 2 HCl + Br.sub.2 205 .sub.17Cl Cl.sub.2 + ClF.sub.3 .fwdarw. 3 ClF Group 17 4 ClF + 2 H.sub.2O .fwdarw. 2 Cl.sub.2 + 4 HF + O.sub.2 206 .sub.17Cl Cl.sub.2 + ClF.sub.3 .fwdarw. 3 ClF Group 17 ClF + F.sub.2 .fwdarw. ClF.sub.3 207 .sub.17Cl HClO.sub.2 + HClO.sub.3 .fwdarw. 2 ClO.sub.2 + H.sub.2O Group 17 2 ClO.sub.2 + H.sub.2O.sub.2 .fwdarw. 2 HClO.sub.2 + O.sub.2 208 .sub.17Cl HClO.sub.2 + HClO.sub.3 .fwdarw. 2 ClO.sub.2 + H.sub.2O Group 17 6 ClO.sub.2 + 2 H.sub.2O .fwdarw. 4 HClO.sub.3 + Cl.sub.2 + O.sub.2 209 .sub.35Br HBrO.sub.2 + HBrO.sub.3 .fwdarw. 2 BrO.sub.2.sup. + H.sub.2O Group 17 BrO.sub.2.sup. + H.sup.+ + Ce.sup.3+ .fwdarw. HBrO.sub.2 + Ce.sup.4+ 210 .sub.35Br HBrO + HBrO.sub.2 .fwdarw. Br.sub.2O.sub.2 + H.sub.2O Group 17 Br.sub.2O.sub.2 .fwdarw. 2 BrO.sup. BrO.sup. + H.sup.+ + Ce.sup.3+ .fwdarw. HBrO + Ce.sup.4+ 211 .sub.35Br HBr + HBrO .fwdarw. Br.sub.2 + H.sub.2O Group 17 Br.sub.2 + H.sub.2 .fwdarw. 2 HBr 212 .sub.35Br HBr + HBrO .fwdarw. Br.sub.2 + H.sub.2O Group 17 Br.sub.2 + Cl.sub.2 + 2 H.sub.2O .fwdarw. 2 HBrO + 2 HCl 213 .sub.35Br 5 HBr + HBrO.sub.3 .fwdarw. 3 Br.sub.2 + 3 H.sub.2O Group 17 Br.sub.2 + HNO.sub.2 + H.sub.2O .fwdarw. 2 HBr + HNO.sub.3 214 .sub.35Br 5 HBr + HBrO.sub.3 .fwdarw. 3 Br.sub.2 + 3 H.sub.2O Group 17 Br.sub.2 + 5 HOCl + H.sub.2O .fwdarw. 2 HBrO.sub.3 + 5 HCl 215 .sub.53I HIO.sub.2 + I.sup. + H.sup.+ .fwdarw. 2 HOI Group 17 HOI + HClO.sub.2 .fwdarw. HIO.sub.2 + HOCl 216 .sub.53I HIO.sub.2 + I.sup. + H.sup.+ .fwdarw. 2 HOI Group 17 HOI + HSO.sub.3.sup. .fwdarw. I.sup. + HSO.sub.4.sup. + H.sup.+ 217 .sub.53I HIO.sub.2 + I.sup. + H.sup.+ .fwdarw. 2 HOI Group 17 3 HOI + 3 NaOH .fwdarw. 2 I.sup. + IO.sub.3.sup. + 3 Na.sup.+ + 3 H.sub.2O 218 .sub.53I IO.sub.3.sup. + 5 I.sup. + 6 H.sup.+ .fwdarw. 3 I.sub.2 + 3 H.sub.2O Group 17 5 ClO.sub.2.sup. + 2 I.sub.2 + 2 H.sub.2O .fwdarw. 5 Cl.sup. + 4 IO.sub.3.sup. + 4 H.sup.+ 219 .sub.53I IO.sub.3 + 5 I.sup. + 6 H.sup.+ .fwdarw. 3 I.sub.2 + 3 H.sub.2O Group 17 I.sub.2 + H.sub.2S .fwdarw. 2 I.sup. + 2 H.sup.+ + S 220 .sub.53I HOI + I.sup. + H.sup.+ .fwdarw. I.sub.2 + H.sub.2O Group 17 I.sub.2 + H.sub.2SO.sub.3 + H.sub.2O .fwdarw. 2 I.sup. + 4 H.sup.+ + SO.sub.4.sup.2 221 .sub.53I HOI + I.sup. + H.sup.+ .fwdarw. I.sub.2 + H.sub.2O Group 17 I.sub.2 + 2 HOCl .fwdarw. 2 HOI + Cl.sub.2 222 .sub.53I HIO.sub.3 + 2 I.sub.2 + 5 HCl .fwdarw. 5 ICl + 3 H.sub.2O Group 17 2 ICl .fwdarw. I.sub.2 + Cl.sub.2 223 .sub.54Xe XeF.sub.4 + Xe .fwdarw. 2 XeF.sub.2 Group 18 XeF.sub.2 + F.sub.2 .fwdarw. XeF.sub.4 224 .sub.54Xe XeF.sub.4 + Xe .fwdarw. 2 XeF.sub.2 Group 18 2 XeF.sub.2 + 2 H.sub.2O .fwdarw. 2 Xe + O.sub.2 + 4 HF 225 .sub.54Xe 2 XeF.sub.6 + Xe .fwdarw. 3 XeF.sub.4 Group 18 XeF.sub.4 + F.sub.2 .fwdarw. XeF.sub.6 226 .sub.54Xe 2 XeF.sub.6 + Xe .fwdarw. 3 XeF.sub.4 Group 18 XeF.sub.4 + 2 H.sub.2 .fwdarw. Xe + 4 HF The arrows in this table do not mean that the reactions are irreversible, but just indicate the autocatalytic direction. Autocatalysts are shown by bold fonts. Sometimes, a chemical species may contain multiple atoms of the same element but these atoms have different oxidation numbers, for example Mn.sub.3O.sub.4 and S.sub.2O.sub.3.sup.2; in these cases, the average oxidation number of the element is considered. Ln: lanthanoid. An: actinoid. Note: Table 2 encompasses all the comproportionation-based autocatalytic cycles in Table 1 as well as additional comproportionation-based autocatalytic cycles.
TABLE-US-00003 TABLE 3 Examples of Broad-sense Comproportionation- based Autocatalytic Cycles. Serial Reactions B1 O.sub.2SCl.sub.2 + O.sub.2SF.sub.2 .fwdarw. 2 O.sub.2SFCl O.sub.2SFCl + KSO.sub.2F .fwdarw. O.sub.2SF.sub.2 + KCl + SO.sub.2 B2 Ca(HCO.sub.3).sub.2 + H.sup.+ + HSO.sub.3.sup. .fwdarw. 2 H.sub.2CO.sub.3 + CaSO.sub.3 CaCO.sub.3 + H.sub.2CO.sub.3 .fwdarw. Ca(HCO.sub.3).sub.2 B3 Ca(HCO.sub.3).sub.2 + CaO .fwdarw. 2 CaCO.sub.3 + H.sub.2O CaCO.sub.3 + H.sub.2CO.sub.3 .fwdarw. Ca(HCO.sub.3).sub.2 B4 Ca(HCO.sub.3).sub.2 + CaO .fwdarw. 2 CaCO.sub.3 + H.sub.2O CaCO.sub.3 .fwdarw. CaO + CO.sub.2 B5 2 CaO + CaC.sub.2 .fwdarw. 3 Ca + 2 CO Ca + 2 C .fwdarw. CaC.sub.2 B6 2 CaO + CaC.sub.2 .fwdarw. 3 Ca + 2 CO 2 Ca + O.sub.2 .fwdarw. 2 CaO B7 Ca(OH).sub.2 + H.sub.2CO.sub.3 .fwdarw. CaCO.sub.3 + 2 H.sub.2O CaO + H.sub.2O .fwdarw. Ca(OH).sub.2 B8 Ca.sub.3(PO.sub.4).sub.2 + 4 H.sub.3PO.sub.4 .fwdarw. 3 Ca(H.sub.2PO.sub.4).sub.2 Ca(H.sub.2PO.sub.4).sub.2 + 2 CaCO.sub.3 .fwdarw. Ca.sub.3(PO.sub.4).sub.2 + 2 CO.sub.2 + 2 H.sub.2O B9 Ca.sub.3(PO.sub.4).sub.2 + 4 H.sub.3PO.sub.4 .fwdarw. 3 Ca(H.sub.2PO.sub.4).sub.2 Ca(H.sub.2PO.sub.4).sub.2 + 2 HCl .fwdarw. CaCl.sub.2 + 2 H.sub.3PO.sub.4 B10 Na.sub.2S + H.sub.2S .fwdarw. 2 NaHS NaHS + NaOH .fwdarw. Na.sub.2S + H.sub.2O B11 Na.sub.2S + H.sub.2S .fwdarw. 2 NaHS NaHS + HCl .fwdarw. H.sub.2S + NaCl B12 Na.sub.2CO.sub.3 + H.sub.2CO.sub.3 .fwdarw. 2 NaHCO.sub.3 NaHCO.sub.3 + NaOH .fwdarw. Na.sub.2CO.sub.3 + H.sub.2O B13 Na.sub.2O + H.sub.2O .fwdarw. 2 NaOH 2 NaOH + 2 Na .fwdarw. 2 Na.sub.2O + H.sub.2 B14 5 NaN.sub.3 + NaNO.sub.3 .fwdarw. 3 Na.sub.2O + 8 N.sub.2 Na.sub.2O + H.sub.2O .fwdarw. 2 NaOH NaOH + HNO.sub.3 .fwdarw. NaNO.sub.3 + H.sub.2O B15 2 ZnO + ZnS + 3 Se .fwdarw. 3 ZnSe + SO.sub.2 2 ZnSe + 3 O.sub.2 .fwdarw. 2 ZnO + 2 SeO.sub.2 B16 ZnS + 2 ZnO .fwdarw. 3 Zn + SO.sub.2 Zn + 2 H.sub.2O .fwdarw. Zn(OH).sub.2 + H.sub.2 Zn(OH).sub.2 .fwdarw. ZnO + H.sub.2O B17 ZnS + 2 ZnO .fwdarw. 3 Zn + SO.sub.2 Zn + 2 HCl .fwdarw. ZnCl.sub.2 + H.sub.2 ZnCl.sub.2 + H.sub.2S .fwdarw. ZnS + 2 HCl B18 4 ZnO + ZnCl.sub.2 + 5 H.sub.2O .fwdarw. Zn.sub.5(OH).sub.8Cl.sub.2H.sub.2O Zn.sub.5(OH).sub.8Cl.sub.2H.sub.2O + 8 HCl .fwdarw. 5 ZnCl.sub.2 + 9 H.sub.2O B19 6 NaAlO.sub.2 + Al.sub.2(SO.sub.4).sub.3 + 12 H.sub.2O .fwdarw. 3 Na.sub.2SO.sub.4 + 8 Al(OH).sub.3 Al(OH).sub.3 + NaOH .fwdarw. NaAlO.sub.2 + 2 H.sub.2O B20 Cu.sub.2S + 2 CuO .fwdarw. SO.sub.2 + 4 Cu 2 Cu + 2 NO .fwdarw. N.sub.2 + 2 CuO B21 3 AsS.sub.2.sup. + AsO.sub.3.sup.3 + 6 H.sup.+ .fwdarw. 2 As.sub.2S.sub.3 + 3 H.sub.2O As.sub.2S.sub.3 + HS.sup. + NH.sub.3 .fwdarw. 2 AsS.sub.2.sup. + NH.sub.4.sup.+ B22 AsCl.sub.3 + As.sub.2O.sub.3 .fwdarw. 3 AsOCl AsOCl + HCl .fwdarw. As(OH)Cl.sub.2 As(OH)Cl.sub.2 + HCl .fwdarw. AsCl.sub.3 + H.sub.2O B23 H.sub.2S.sub.2O.sub.7 + H.sub.2O .fwdarw. 2 H.sub.2SO.sub.4 H.sub.2SO.sub.4 + SO.sub.3 .fwdarw. H.sub.2S.sub.2O.sub.7 B24 H.sub.2Cr.sub.2O.sub.7 + H.sub.2O .fwdarw. 2 H.sub.2CrO.sub.4 H.sub.2CrO.sub.4 + CrO.sub.3 .fwdarw. H.sub.2Cr.sub.2O.sub.7 B25 FeS.sub.2 + Fe .fwdarw. 2 FeS FeS + C + CaO .fwdarw. Fe + CO + CaS B26 2 CoO + Co(CN).sub.2 .fwdarw. 3 Co + 2 CO + N.sub.2 Co + H.sub.2O .fwdarw. CoO + H.sub.2 B27 5 B.sub.2H.sub.6 + 2 BBr.sub.3 .fwdarw. 6 B.sub.2H.sub.5Br B.sub.2H.sub.5Br + (CH.sub.3).sub.2SbH .fwdarw. B.sub.2H.sub.6 + (CH.sub.3).sub.2SbBr B28 B.sub.4C + BO .fwdarw. 5 B + CO B + N.sub.2O .fwdarw. BO + N.sub.2 B29 B.sub.4C + BO .fwdarw. 5 B + CO 4 B + C .fwdarw. B.sub.4C B30 B.sub.2O.sub.3 + 2 KBH.sub.4 .fwdarw. 4 B + 2 KOH + H.sub.2O + 2 H.sub.2 4 B + 3 O.sub.2 .fwdarw. 2 B.sub.2O.sub.3 B31 6 AlN + Al.sub.2(SO.sub.4).sub.3 + 24 H.sub.2O .fwdarw. 8 Al(OH).sub.3 + 3 (NH.sub.4).sub.2SO.sub.4 2 Al(OH).sub.3 + 3 H.sub.2SO.sub.4 .fwdarw. Al.sub.2(SO.sub.4).sub.3 + 6 H.sub.2O B32 6 AlN + Al.sub.2(SO.sub.4).sub.3 + 24 H.sub.2O .fwdarw. 8 Al(OH).sub.3 + 3 (NH.sub.4).sub.2SO.sub.4 2 Al(OH).sub.3 .fwdarw. Al.sub.2O.sub.3 + 3 H.sub.2O Al.sub.2O.sub.3 + 3 C + N.sub.2 .fwdarw. 2 AlN + 3 CO B33 Al.sub.2(SO.sub.4).sub.3 + 2 Na.sub.3AlF.sub.6 .fwdarw. 4 AlF.sub.3 + 3 Na.sub.2SO.sub.4 AlF.sub.3 + 3 H.sub.2O .fwdarw. Al(OH).sub.3 + 3 HF 2 Al(OH).sub.3 + 3 H.sub.2SO.sub.4 .fwdarw. Al.sub.2(SO.sub.4).sub.3 + 6 H.sub.2O B34 AlCl.sub.3 + 3 LiAlH.sub.4 .fwdarw. 4 AlH.sub.3 + 3 LiCl 2 AlH.sub.3 + 2 BCl.sub.3 .fwdarw. 2 AlCl.sub.3 + B.sub.2H.sub.6 B35 CO.sub.2 + CS.sub.2 + 4 Cu .fwdarw. 2 CO + 2 Cu.sub.2S CO + FeO .fwdarw. Fe + CO.sub.2 B36 CO + H.sub.2 + CaCN.sub.2 .fwdarw. CaO + 2 HCN HCN + H.sub.2O .fwdarw. CO + NH.sub.3 B37 PbS + 3 PbSO.sub.4 .fwdarw. 4 PbO + 4 SO.sub.2 PbO + H.sub.2S .fwdarw. PbS + H.sub.2O B38 PbS + 3 PbSO.sub.4 .fwdarw. 4 PbO + 4 SO.sub.2 PbO + SO.sub.3 .fwdarw. PbSO.sub.4 B39 PbS + 2 PbO .fwdarw. 3 Pb + SO.sub.2 Pb + H.sub.2S .fwdarw. PbS + H.sub.2 B40 PbS + 2 PbO .fwdarw. 3 Pb + SO.sub.2 2 Pb + O.sub.2 .fwdarw. 2 PbO B41 Pb(CH.sub.3).sub.3(C.sub.2H.sub.5) + Pb(CH.sub.3)(C.sub.2H.sub.5).sub.3 .fwdarw. 2 Pb(CH.sub.3).sub.2(C.sub.2H.sub.5).sub.2 Pb(CH.sub.3).sub.4 + Pb(CH.sub.3).sub.2(C.sub.2H.sub.5).sub.2 .fwdarw. 2 Pb(CH.sub.3).sub.3(C.sub.2H.sub.5) B42 Pb(CH.sub.3).sub.3(C.sub.2H.sub.5) + Pb(CH.sub.3)(C.sub.2H.sub.5).sub.3 .fwdarw. 2 Pb(CH.sub.3).sub.2(C.sub.2H.sub.5).sub.2 Pb(C.sub.2H.sub.5).sub.4 + Pb(CH.sub.3).sub.2(C.sub.2H.sub.5).sub.2 .fwdarw. 2 Pb(CH.sub.3)(C.sub.2H.sub.5).sub.3 B43 5 H.sub.3PO.sub.4 + POCl.sub.3 .fwdarw. 3 H.sub.4P.sub.2O.sub.7 + 3 HCl H.sub.4P.sub.2O.sub.7 + H.sub.2O .fwdarw. 2 H.sub.3PO.sub.4 B44 2 HF + SiF.sub.4 .fwdarw. H.sub.2SiF.sub.6 H.sub.2SiF.sub.6 + 4 H.sub.2O .fwdarw. 6 HF + H.sub.4SiO.sub.4 The arrows in this table do not mean that the reactions are irreversible, but just indicate the autocatalytic direction. Autocatalysts are shown by bold fonts.
[0069] The word illustrative is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as illustrative is not necessarily to be construed as preferred or advantageous over other aspects or designs. Further, for the purposes of this disclosure and unless otherwise specified, a or an means one or more.
[0070] The foregoing description of illustrative embodiments of the invention has been presented for purposes of illustration and of description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and as practical applications of the invention to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.
[0071] If not already included, all numeric values of parameters in the present disclosure are proceeded by the term about which means approximately. This encompasses those variations inherent to the measurement of the relevant parameter as understood by those of ordinary skill in the art. This also encompasses the exact value of the disclosed numeric value and values that round to the disclosed numeric value.