A SERIES of new compounds of phosphorus, nitrogen, and chlorine, and likewise a series of acids derived from them, have been discovered by Mr. H. N. Stokes, and an account of them is contributed to the American Chemical Journal. A familiar compound of the three elements in question, the chlorophos-phuret of nitrogen, discovered by Liebig in 1832, has been the subject of frequent study, and its nature has comparatively recently been very fully demonstrated by Dr. Gladstone. It has been shown, from vapour density determinations, that this remarkably stable compound, which may be distilled in steam and boiled with acids and alkalies without appreciable change, possesses the molecular composition P3N3C16. Mr. Stokes now shows that this substance is only one of a homologous series of compounds having the general formula (PNCl2)n, and that these are the chlorides of a series of acids (PNO2H2)n, which he terms metaphosphimic acids. The second member of the series, (PNC12)4, has been isolated from the product of Dr Gladstone's reaction for the preparation of (PNC12)3, that between phosphorus pentachloride and ammonium chloride; it is a substance almost as stable as the triple compound, and yields on saponification the acid (PNO2H2)4, which is likewise a stable body. Moreover, the acid corresponding to the triple compound has been isolated, and also a higher chloride (PNCl2)x of an oily character, and whose molecular weight has not yet been ascertained. In describing his repetition of Dr. Gladstone's work, Mr. Stokes incidentally mentions the interesting circumstance that the triple compound readily forms enormous crystals, well-developed prisms several inches long and of considerable thickness being frequently deposited from benzene, and indeed their size appears only to be limited by that of the containing vessel and the bulk of solution. These crystals melt at 114°. The quadruple compound melts at I23°˙5, and boils at the normal pressure at 256°˙5. It crystallises well in colourless prisms, which are usually much smaller than those of the triple compound, and exhibit great tendency to develop an a cicular character. It is less soluble in alcohol and benzene than the latter compound; it may be recrystallised from glacial acetic acid, but it exhibits a great aversion for water, not being wet by it, and consequently the crystals float on water. It dissolves in hot concentrated oil of vitriol, but upon boiling most of it sublimes unchanged, an evidence of its great stability. Its vapour is endowed with a pleasant aromatic odour, but inhalation of more than traces is followed in two or three hours by alarming difficulty in breathing and persistent irritation of the air passages. Its vapour density was determined in an atmosphere of hydrogen, and indicated the quadruple formula. Even boiling water exerts only a very slight action upon it; but a smooth decomposition is effected by dissolving in ether, and repeatedly agitating with water. The acid produced is deposited from the water in crystals having the composition (PNO2H2)4 + 2H20. This interesting acid readily decomposes soluble chlorides, nitrates, and sulphates, forming three series of salts, in which respectively one-fourth, one-half, and all the hydrogen is replaced by the metal. The free acid is so highly stable that it may be boiled for hours with nitric acid or aqua regia without decomposition Further details concerning it, and the other compounds isolated, will shortly be published.
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New Compounds of Phosphorus, Nitrogen, and Chlorine. Nature 51, 592–593 (1895). https://doi.org/10.1038/051592a0