The present invention relates to a composition for the protection against solar radiation, consisting of an organic matrix, preferably a gelatin, and hydroxyapatite nanoparticles modified by the substitution of part of the phosphorus with titanium, and part of the calcium with iron.

A process for producing a calcium phosphate reactant, according to which: in a first step, use is made of a source of calcium and a source of phosphate ions in water, in a molar ratio that is adjusted so as to obtain a Ca/P molar ratio of between 0.5 and 1.6, and the source of calcium is reacted with the phosphate ions at a pH of between 2 and 8, in order to obtain a suspension (A) of calcium phosphate, and in a second step, added to the suspension (A) are an alkaline compound comprising hydroxide ions in order to set a pH of more than 8 and an additional source of calcium in order to obtain a suspension (B) of calcium phosphate reactant having a Ca/P molar ratio of more than 1.6. A calcium phosphate reactant obtainable by such a process.

A process for producing a calcium phosphate reactant, according to which: in a first step, use is made of a source of calcium and a source of phosphate ions in water, in a molar ratio that is adjusted so as to obtain a Ca/P molar ratio of between 0.5 and 1.6, and the source of calcium is reacted with the phosphate ions at a pH of between 2 and 8, in order to obtain a suspension (A) of calcium phosphate, and in a second step, added to the suspension (A) are an alkaline compound comprising hydroxide ions in order to set a pH of more than 8 and an additional source of calcium in order to obtain a suspension (B) of calcium phosphate reactant having a Ca/P molar ratio of more than 1.6. A calcium phosphate reactant obtainable by such a process.

The present invention provides: a method for producing a shaped product comprising octacalcium phosphate and having a volume of 2.0 mm.sup.3 or more, comprising immersing a precursor ceramic composition containing at least one of Ca and PO.sub.4 in composition, having a solubility in H.sub.2O higher than that of octacalcium phosphate, and having a volume greater than 2.0 mm.sup.3, in a solution containing a component which is not contained in the precursor ceramic composition, among the components Ca, PO.sub.4 and H.sub.2O, which are components of octacalcium phosphate to allow the precursor ceramic composition to react, thereby converting at least a part of the precursor ceramic composition into octacalcium phosphate; and the like.

The present invention provides that powder is mainly constituted from secondary particles of hydroxyapatite. The secondary particles are obtained by drying a slurry containing primary particles of hydroxyapatite and aggregates thereof and granulating the primary particles and the aggregates. A bulk density of the powder is 0.65 g/mL or more and a specific surface area of the secondary particles is 70 m.sup.2/g or more. The powder of the present invention has high strength and is capable of exhibiting superior adsorption capability when it is used for an adsorbent an adsorption apparatus has.

Process of acid attack with sulphuric acid of a phosphate source comprising calcium or not comprising calcium for a predetermined time period ranging from 20 to 180 minutes in the conditions wherein the molar ratio of sulphate from the sulphuric acid and possibly from the phosphate source to the calcium present in the phosphate source ranges from 0.6 to 0.8, and the content in P.sub.2O.sub.5 in the attack tank is of less than 6%.

The present invention provides that powder is mainly constituted from secondary particles of hydroxyapatite. The secondary particles are obtained by drying a slurry containing primary particles of hydroxyapatite and aggregates thereof and granulating the primary particles and the aggregates. A bulk density of the powder is 0.65 g/mL or more and a specific surface area of the secondary particles is 70 m.sup.2/g or more. The powder of the present invention has high strength and is capable of exhibiting superior adsorption capability when it is used for an adsorbent an adsorption apparatus has.

The present invention provides: a method for producing a shaped product comprising octacalcium phosphate and having a volume of 2.0 mm.sup.3 or more, comprising immersing a precursor ceramic composition containing at least one of Ca and PO.sub.4 in composition, having a solubility in H.sub.2O higher than that of octacalcium phosphate, and having a volume greater than 2.0 mm.sup.3, in a solution containing a component which is not contained in the precursor ceramic composition, among the components Ca, PO.sub.4 and H.sub.2O, which are components of octacalcium phosphate to allow the precursor ceramic composition to react, thereby converting at least a part of the precursor ceramic composition into octacalcium phosphate; and the like.

According to the present invention, provided is a carbonate- and magnesium-substituted hydroxyapatite having a particle size of 5 nm or more and 60 nm or less, wherein a portion of the calcium atoms in the hydroxyapatite are substituted with magnesium atoms and a portion of phosphate groups are substituted with carbonate groups.

An object of the present invention is to provide anhydrous dibasic calcium phosphate having good powder flowability and good dispersibility in water. An anhydrous dibasic calcium phosphate powder containing agglomerated particles formed by agglomerating anhydrous dibasic calcium phosphate particles having a modal pore diameter/mean particle diameter ratio of 0,2 to 0,34 exhibits good powder flowability and good dispersibility in water.