Chemistry : general, medical, and pharmaceutical including the chemistry of the ; a manual on the general principles of the science, and their applications in medicine and pharmacy . inserted, and asecond funnel inverted, so that its mouthrests within the mouth of the first, is anefficient and convenient arrangement ofapparatus for this process, especially if theoperation be conducted slowly. Solution of phosphoric acid evaporatedleaves a residue which melts at a low redheat, yielding pyrophosphoric acid, and,finally, metaphosphoric acid (Glacial Phos-phoric Acid). Phosphoric
Chemistry : general, medical, and pharmaceutical including the chemistry of the ; a manual on the general principles of the science, and their applications in medicine and pharmacy . inserted, and asecond funnel inverted, so that its mouthrests within the mouth of the first, is anefficient and convenient arrangement ofapparatus for this process, especially if theoperation be conducted slowly. Solution of phosphoric acid evaporatedleaves a residue which melts at a low redheat, yielding pyrophosphoric acid, and,finally, metaphosphoric acid (Glacial Phos-phoric Acid). Phosphoric acid is also easily made fromamorphous phosphorus (Mattison). Quantivalence. — The elements repre-sented by the formular P04 are those characteristic of grouping is trivalent; hence there may exist trimetallic or normalphosphates (M3P04), dimetallic acid phosphates (M2HP04), mono-metallic acid phosphates (MH2P04), and, lastly, trihydric phosphate(H3P04) or common phosphoric acid. These are the ordinary phos-phates met with in nature or used in pharmacy; the rarer pyrophos-phates and metaphosphates, as well as the phosphites and hypo-phosphites, will be mentioned Analytical Reactions ( Tests). First Analytical Reaction. — To an aqueous solution of aphosphate (e. g. Na2HP04) add solution of sulphate of magne-sium with which chloride of ammonium and ammonia havebeen mixed ; a white crystalline precipitate of ammonio-mag-nesium phosphate falls (MgAmPOJ. Chloride of ammonium is added to prevent the precipitation ofhydrate of magnesium. Arseniates, which have close analogy tophosphites, give a similar precipitate with the magnesium reagent. Second Analytical Reaction.—To a neutral aqueous solutionof a phosphate add solution of nitrate of silver; light-yellowphosphate of silver (Ag3P04) is precipitated. To a portion ofthe precipitate add ammonia ; it dissolves. To another portionadd nitric acid ; it dissolves. By this reaction phosphates may PHOSPHA
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