A carbon dioxide/co-fluid mixture is provided for use in a refrigeration cycle in which the carbon dioxide is alternately absorbed and desorbed from the co-fluid. Suitable co-fluids are selected from the class of alkoxylated carboxylic amides, wherein the amides are cyclic or non-cyclic. It has been discovered that N-2,5,8,11-tetraoxadodecyl-2-pyrrolidinone and its homologs exhibit an advantageous property of a high rate of desorption at lower temperatures.

A carbon dioxide/co-fluid mixture is provided for use in a refrigeration cycle in which the carbon dioxide is alternately absorbed and desorbed from the co-fluid. Suitable co-fluids are selected from the class of alkoxylated carboxylic amides, wherein the amides are cyclic or non-cyclic. It has been discovered that N-2,5,8,11-tetraoxadodecyl-2-pyrrolidinone and its homologs exhibit an advantageous property of a high rate of desorption at lower temperatures.

The invention provides a solid lubricant in the form of film containing a triazine compound or the salt thereof, such as melamine cyanurate or the like.

A lubricant including an ionic liquid, which includes a conjugate acid (B.sup.+) and a conjugate base (X.sup.), and is protic, wherein the ionic liquid is represented by the following general formula (1):

##STR00001##

where R.sup.1 and R.sup.2 each represent a hydrogen atom or R.sup.1 and R.sup.2 form a benzene ring together with carbon atoms to which R.sup.1 and R.sup.2 are bonded, and R.sup.3 represents a straight-chain hydrocarbon group having 10 or more carbon atoms in the general formula (1).

A lubricant including an ionic liquid, which includes a conjugate acid (B.sup.+) and a conjugate base (X.sup.), and is protic, wherein the ionic liquid is represented by the following general formula (1):

##STR00001##

where R.sup.1 and R.sup.2 each represent a hydrogen atom or R.sup.1 and R.sup.2 form a benzene ring together with carbon atoms to which R.sup.1 and R.sup.2 are bonded, and R.sup.3 represents a straight-chain hydrocarbon group having 10 or more carbon atoms in the general formula (1).

A lubricant including: an ionic liquid, which includes a conjugate acid (B.sup.+) and a conjugate base (X.sup.), and is protic, wherein the ionic liquid is represented by the following general formula (1), and wherein the conjugate base is a conjugate base of sulfonic acid, a conjugate base of sulfonimide, or a conjugate base of trisulfonylmethide:

##STR00001##

where R.sup.1 and R.sup.2 each represent a hydrogen atom or R.sup.1 and R.sup.2 form a benzene ring together with carbon atoms to which R.sup.1 and R.sup.2 are bonded, R.sup.3 represents a to straight-chain hydrocarbon group having 10 or more carbon atoms, and R.sup.4 represents a hydrogen atom or a hydrocarbon group in the general formula (1).

A lubricant including an ionic liquid, which contains a conjugate acid (B.sup.+) and a conjugate base (X.sup.) and is aprotic, wherein the conjugate acid contains a straight-chain hydrocarbon group having 10 or more carbon atoms, and wherein an acid that is a source of the conjugate base has a pKa in water of 0 or less.

A lubricant including an ionic liquid, which contains a conjugate acid (B.sup.+) and a conjugate base (X.sup.) and is aprotic, wherein the conjugate acid contains a straight-chain hydrocarbon group having 10 or more carbon atoms, and wherein an acid that is a source of the conjugate base has a pKa in water of 0 or less.

A lubricant including an ionic liquid, which includes a conjugate acid (B.sup.+) and a conjugate base (X.sup.), and is protic, wherein the conjugate acid includes a straight-chain hydrocarbon group having 10 or more carbon atoms, and wherein the conjugate base is represented by the following general formula (1):

##STR00001##

where n is an integer of from 0 to 6 in the general formula (1).

A lubricant including an ionic liquid, which includes a conjugate acid (B.sup.+) and a conjugate base (X.sup.), and is protic, wherein the conjugate acid includes a straight-chain hydrocarbon group having 10 or more carbon atoms, and wherein the conjugate base is represented by the following general formula (1):

##STR00001##

where n is an integer of from 0 to 6 in the general formula (1).