. Chemistry: general, medical, and pharmaceutical, including the chemistry of the U. S. Pharmacopia. A manual on the general principles of the science, and their applications in medicine and pharmacy. made by decomposing phosphorus bromide by water: 270 THE ACIDULOUS RADICALS. PBr5 -f- 4H20 = 5HBr + H3P04. A small quantity is prepared byplacing seven or eight drops of bromine at the bottom of a test-tube,putting in fragments of glass to the height of about an inch or two,then ten or eleven grains of phosphorus, then another inch of glass,and finally a couple of inches of glass fragments slight
. Chemistry: general, medical, and pharmaceutical, including the chemistry of the U. S. Pharmacopia. A manual on the general principles of the science, and their applications in medicine and pharmacy. made by decomposing phosphorus bromide by water: 270 THE ACIDULOUS RADICALS. PBr5 -f- 4H20 = 5HBr + H3P04. A small quantity is prepared byplacing seven or eight drops of bromine at the bottom of a test-tube,putting in fragments of glass to the height of about an inch or two,then ten or eleven grains of phosphorus, then another inch of glass,and finally a couple of inches of glass fragments slightly wettedwith water, a delivery-tube being fitted by a cork. The phosphoruscombines readily, almost violently, with the bromine as soon as thevapor of the latter, aided by a little warmth from a flame, rises tothe region of the phosphorus. The phosphorus bromide thus formedthen suffers decomposition by the water of the moist glass, phos-phoric and phosphorous acids being produced. The hydrobromicacid gas passes over (heat being applied in the after part of theoperation) and may be condensed in water or in solution of latter solution on evaporation yields ammonium bromide. Fig. Preparation of Hydrobromic Acid. Acidum Hydrobromicum Dilutum, U. S. P.—Pass sulphuretted-hydrogen gas through bromine covered with water, and, when allbromine has disappeared, distil the mixture. The distillate, whendiluted until it has a sp. gr. of , contains 33 per cent, of until the sp. gr. is , it contains 10 per cent, of HBr,and is then of official strength. 10Br2 + 4H2S + 8H20 = 20HBr + 2H2S04 + S2. Potassium Bromide (KBr) is very largely employed in pharmacy,and is the salt, therefore, which may be used in studying the reac-tions of this acidulous radical. The official method of making thesalt has been alluded to under the salts of potassium (p. 77). Other bromides are seldom used; they may be prepared in thesame way as, and closely resemble, the correspond
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