Abstract: A process for the preparation of a hydroxyapatite, which is suitable as a tooth-cleaning substance, by precipitation from aqueous phosphoric acid and calcium hydroxide solution, in which a calcium-doped phosphoric acid solution is fed to an intensive mixer with a suspension of calcium hydroxide/oxide in a molar ratio of Ca:P=1.667 corresponding to the hydroxyapatite of and reacted there at precipitation temperatures of 60.degree.-100.degree. C., preferably 80.degree.-90.degree. C. and a pH of 4-8, preferably of 6.5-7.5. Also disclosed in a tooth-cleaning substance containing the hydroxyapatite.

Abstract: The present invention provides a process and apparatus for the production of coarse-grained dicalcium phosphate anhydride, at least 95% of which consists of particles with a grain diameter of >45 .mu.m, wherein, at a temperature of 60.degree. to 100.degree. C., a highly reactive calcium component, for example freshly slaked milk of lime or an aqueous slurry or suspension of calcium hydroxide and/or calcium carbonate, is introduced directly into the stirrer zones of a vessel containing aqueous phosphoric acid and having one or more turbulent stirrer zones. An equivalent amount of aqueous phosphoric acid is introduced into another zone of the vessel, the speed of introduction being so regulated that a pH value of 3.0 to 4.5 is obtained in the stirrer zone and the whole batch or a continuously or semi-continuously removed part thereof is cooled to 40.degree. to 60.degree. C. The removed part then is mixed with an additional calcium component, for example milk of lime, to obtain a pH value of from 5.5 to 6.

Abstract: A process for the preparation of coarse-particle dicalcium phosphate dihydrate having a virtually spherical crystal shape and a particle size range between about 63 and 450 .mu.m, preferably between about 90 and 300 .mu.m, by reacting pure aqueous phosphoric acid with aqueous suspensions of precipitated chalks, wherein an amount of suspension corresponding to the reaction product formed is removed continuously or semicontinuously and the dicalcium phosphate dihydrate is separated off, washed and dried. Also disclosed is coarse-particle dicalcium phosphate dihydrate produced by the above process.

Abstract: Disclosed are novel N-(hydroxy methyl)-1-amino alkane-1,1-diphosphonic acids and N,N-Bis-(hydroxy-methyl)-1-amino alkane-1,1-diphosphonic acids, preferably N-(hydroxy methyl)-1-amino ethane-1,1-diphosphonic acid, N,N-Bis-(hydroxy methyl)-1-amino ethane-1,1-diphosphonic acid, and their water-soluble salts. Also disclosed is a method for preparing these compounds by reacting the corresponding 1-amino alkane-1,1-diphosphonic acids with formaldehyde in an alkaline medium at elevated temperature. The new phosphonic acid compounds are excellent stabilizing agents for hydrogen peroxide-containing alkaline bleaching liquors, especially useful for bleaching cellulose fibers and blends thereof with synthetic fibers, such as polyester fibers.

Abstract: Disclosed are novel N-(hydroxy methyl)-1-amino alkane-1,1-diphosphonic acids and N,N-Bis-(hydroxy-methyl)-1-amino alkane-1,1-diphosphonic acids, preferably N-(hydroxy methyl)-1-amino ethane-1,1-diphosphonic acid, N,N-Bis-(hydroxy methyl)-1-amino ethane-1,1-diphosphonic acid, and their water-soluble salts. Also disclosed is a method for preparing these compounds by reacting the corresponding 1-amino alkane-1,1-diphosphonic acids with formaldehyde in an alkaline medium at elevated temperature. The new phosphonic acid compounds are excellent stabilizing agents for hydrogen peroxide-containing alkaline bleaching liquors, especially useful for bleaching cellulose fibers and blends thereof with synthetic fibers, such as polyester fibers.

Abstract: Disclosed are novel N-(hydroxy methyl)-1-amino alkane-1,1-diphosphonic acids and N,N-Bis-(hydroxy-methyl)-1-amino alkane-1,1-diphosphonic acids, preferably N-(hydroxy methyl)-1-amino ethane-1,1-diphosphonic acid, N,N-Bis-(hydroxy methyl)-1-amino ethane-1,1-diphosphonic acid, and their water-soluble salts. Also disclosed is a method for preparing these compounds by reacting the corresponding 1-amino alkane-1,1-diphosphonic acids with formaldehyde in an alkaline medium at elevated temperature. The new phosphonic acid compounds are excellent stabilizing agents for hydrogen peroxide-containing alkaline bleaching liquors, especially useful for bleaching cellulose fibers and blends thereof with synthetic fibers, such as polyester fibers.

Abstract: The present invention is concerned with the novel and highly advantageous process of producing N-acylaminomethanephosphonic acid in a one-step process by reacting a acylonitrile with formaldehyde or a formaldehyde-yielding compound and phosphorous acid in the presence or absence of the solvent at an elevated temperature, preferably at a temperature between about 60.degree. C. and the boiling point of the mixture. The reaction may be carried with or without a polar aprotic solvent and/or an acidic catalyst.

Abstract: Valuable amino alkane diphosphonic acids in which one or both hydrogen atoms of the amino group are substituted by hydroxy alkane groups, and their alkali metal salts and a process of using them are described. Said compounds are highly water-soluble, are stable against hydrolysis even at temperatures exceeding 100.degree. C., and have a high sequestering power so that they can be used advantageously, for instance, in processing aqueous media of considerable hardness, and in suppressing scale and corrosion in aqueous media used for heat treatment of containers.

Abstract: Valuable and highly water soluble N-phosphono methylene mono- and di-amino alkane mono- and polyphosphonic acids which have not only an >N--CH.sub.2 --PO.sub.3 H.sub.2 group but also a C--PO.sub.3 H.sub.2 group in their molecule are produced by reacting amino alkane mono- or diphosphonic acids with formaldehyde and phosphorous acid or alkane nitriles with phosphorous acid, formaldehyde, and concentrated hydrochloric acid. The resulting phosphonic acid compounds are valuable sequestering agents forming complex compounds with bi- and polyvalent metal ions. They are useful for water softening even in substoichiometric amounts, in textile treatment baths, in the paper manufacture, in tanning baths, for the manufacture of liquid fertilizers, and for other purposes.

Abstract: Valuable amino alkane diphosphonic acids in which one or both hydrogen atoms of the amino group are substituted by hydroxy alkane groups, and their alkali metal salts and a process of making them are described. Said compounds are highly water-soluble, are stable against hydrolysis even at temperatures exceeding 100.degree. C., and have a high sequestering power so that they can be used advantageously, for instance, in processing aqueous media of considerable hardness, in baths for treating textiles, in the paper manufacture, in tanning, as liquid fertilizers, and for other purposes.