Q366 PHOSPHORUS, MEDICAL PROPERTIES OF.
— — combustion of phosphorus in chlorine gas ; a white, flaky, volatile compound is formed, which is the perchloride. It is volatile, rising in vapour at It is fusible under pressure, and crystallises in prisms. It reddens dry litmus-paper, owing, as has been suspected, to its acquiring oxygen and hydrogen from the decomposition of the paper. Like the protochloride, it acts strongly upon and decomposes water; but the results are hydrochloric acid and phosphoric, instead of phosphorous, acid.
Phosphide of Nitrogen (PN,f).—This compound cannot be obtained by direct action ; it is the result of the action of ammonia on the chlorides of phosphorus. The changes which occur are effected with difficulty, but the phosphide of nitrogen eventually obtained has the following properties :—lt is a light white powder, and, although formed of very volatile constituents, it remains fixed and infusible even at a red heat, when the access of air is prevented ; but if that be present, white vapours of phosphoric acid are formed. This compound is remarkable, also, for its indifference even to the most powerful reagents; it is insoluble in water and in acids, nitric acid even attack ing it only after long continued exposure to it. Chlorine and sulphur do not act upon it; it is insoluble in alkaline solutions, but when heated with solid hydrate of potash, ammonia is evolved. According to Gerhardt, it contains hydrogen, and its formula is Sulphur and Phosphorus may be made to combine in all proportions by fusion in an exhausted flask or under water ; but the operation requires great caution. The resulting sulphides are very inflammable,
and mostly crystalline.
Phosphorus and Iodine. [IoDINE.] Phosphorus and Bromine. [Bsostrics.] Phosphorus may be made to combine with the greater number of the metals ; the most important of these compounds (phosphides) will be found under each particular metal.
Detection of is very poisonous. It is readily detected in a mixture containing organic matter by placing the suspected mixture in a flask, adding sulphuric acid, suspending a piece of paper streaked with solution of nitrate of silver from the upper part of the flask, and gently heating; if phosphorus be present, the paper will exhibit black marks of phosphide of silver. The absence of sul phuretted hydrogen, and of arsenic, must be previously ascertained ; the one by acetate of lead paper suspended in the flask, the other by Marsh's test.
Detection and Estimation of Phosphoric Acid.—One of the best teats for phosphoric acid is the production of a white crystalline precipitate in the presence of ammonia, on the addition of a soluble salt of mag nesia. The resulting ammonia-phosphate of magnesia, on being ignited, is converted into phosphate of magncsis,which contains 63'33 per cent. of phosphoric acid.