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shaken a short time with 10 per cent ammonia, but one amide appears to be formed. As soon as a few drops of the ether solution leave, on evaporation, a residue completely soluble in hot water, indicating complete transformation of the chloride, it is dried over calcium chloride and allowed to evaporate spontaneously, whereby a substance crystallizing in needles is deposited. The product, which appeared homogeneous on microscopic examination, was directly analyzed.

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The yield was 67 per cent of the theoretical, some of the chloride having been further decomposed and dissolved by the ammonia.

Triphosphonitrilic chloramide is quite soluble in ether, and less soluble in hot benzene, from which it crystallizes in long tufts of delicate hairs. It is easily soluble in alcohol, and from the concentrated alcoholic solution it is precipitated by water. Its stability toward water is striking; cold water dissolves it slightly, and, on rapid evaporation, even on the water bath, much is deposited unaltered; it can even be recrystallized from hot water, though with much decomposition, in needles or short prisms. Its stability in aqueous solution is further indicated by the failure of silver nitrate to give a precipitate except on boiling. Aqueous ammonia has but little action in the cold. On heating its aqueous solution, ammonium chloride and a sirupy acid result. Cold dilute acids have no marked solvent action. It undergoes change gradually at ordinary temperature, and rapidly on heating, without fusing, ammonium chloride and an infusible white substance being the products in the latter case.

Couldridge, by acting on fused triphosphonitrilic chloride with gaseous ammonia, obtained a substance which he regarded as plospham. Both Couldridge and A. W. Hofmann? express the opinion that phospham has the composition expressed by the formula P3N3(NE)3. I regard this as too sweeping. Apart from the fact that its composition varies with the mode of preparation,; it is likely that the true phospham is a mixture of an homologous series of imides (PN.NII)s, derivable from the homologous phosphonitrilic chlorides (PNC1,)..

Tetraphosphonitrilic chloride, P,N,C13.—The new chlorophosphuret of

1 Jour. Chem. Soc. London, Vol. LIII, p. 398.
2 Ber. Deutsch. chem. Gesell., Berlin, Vol. XVII, p. 1911.
* Salzmann : Ber. Deutsch. chem. Gesell., Berlin, Vol. VII, p. 494.

nitrogen, prepared as above described, gave the following results on analysis:

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1. P:N:Cl=1:1.01:1.99. 2. P:N:Cl=1:1.01:1.99.

1 and 2 represent different preparations. The vapor density, determined by Victor Meyer's method, in dry hydrogen at 360o, was:

Calculate 1 for

PN,Clg.

Found

Density

16.03

16. 20

I am indebted to Mr. B. H. Hite, of the Johns Hopkins University, for a series of determinations of the molecular weight by the ebullioscopic method. The following is his statement of the results:

Solvent: Benzene. Molecular elevation, 26.7.
Substance (PNCI,)x.

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These results agree well with the quadruple formula.

The following table gives some of the constants compared with those of P,N.Cle.

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a Gladstone.

240 bAt

Tetraphosphonitrilic chloride forms colorless, brittle prisms, not easily wet by water, and therefore having a strong tendency to float. Superficially, these are not always to be distinguished from those of triphosphonitrilic chloride, but in a general way it may be said that they tend to be much smaller, and are to be measured by millimeters rather than centimeters, and that they tend to vary toward an acicular rather than a tabular form. In alcohol and in benzene it is much less soluble than P2N,Clc. Hot concentrated sulphuric acid dissolves it, and, on boiling, much hydrochloric acid is evolved, but some of the substance sublimes out unchanged. It may be recrystallized from glacial acetic acid; on boiling this solution with zinc dust a little hydrogen phosphide is given off, and the solution contains ammonia. It is noticeably volatile at its fusiug point, its vapor having an odor suggesting, but perceptibly differing from, that of triphosphonitrilic chloride, and less aromatic. The fused substance solidifies to a mass of nearly parallel needles, while triphosphonitrilic chloride gives transparent plates. As mentioned above, its volatility with steam is comparatively slight. If boiled for some time in contact with air, a minute amount of substance is formed, which swells enormously to a clear gelatinous mass in benzene. Alcohol converts it slowly into an oily ether, which aqueous ammonia, on warming, saponifies to tetrametaphosphimic acid.

Action of water on tetraphosphonitrilic chloride.-In its chemical behavior it resembles triphosphonitrilic chloride. It is scarcely acted on by boiling water, yet on prolonged boiling a minute amount of tetrametaphosphimic acid is formed; aqueous fixed alkalies are without perceptible action, while alcoholic alkalies decompose it easily, but the product is mainly something else than tetrametaphosphimic acid.

A smooth decomposition is effected by dissolving in ether and shaking protractedly with water. The first products of this action consist of chlorhydrines, which remain dissolved in the ether, are crystalline, and readily soluble in cold water, from which solution tetrametaphosphimic acid is rapidly deposited in the form of thick needles; the same acid is the final product of the action of water on the ether solution.

The action of water proceeds rather more rapidly than in case of triphosphonitrilic chloride, but many days are required for complete decomposition. The small amount of material at present in my possession made it unadvisable to attempt to isolate any of the chlorhydrines, of which seven are theoretically possible.

Tetrametaphosphimic acid, P.N.O,H, +21,0, will be described in a separate section. It may be remarked here preliminarily that it has highly characteristic properties, is highly crystalline, very difficultly soluble in cold water, and much less soluble in dilute acids; that it readily decomposes soluble chlorides, nitrates, and sulphates, and gives three series of salts, in which, respectively, one-fourth, one half, and all the hydrogen is replaced by metal; many of these show characteristic

forms. The free acid far surpasses the metaphosphoric acids in stability, and may be boiled for hours with nitric acid or aqua regia without much decomposition.

Tetraphosphonitrilic chloride is readily extracted from its ethereal solution by aqueous ammonia, the ammoniacal solution giving tetra metaphosphimic acid on warning with hydrochloric acid. evidence of the formation of chloramides has yet been observed.

Oily phosphonitrilic chloride.—This substance, obtained from the residues as above stated, is possibly a mixture. It is scarcely volatile without decomposition, not volatile with steam, and not acted on by water, except in ethereal solution, when a moderately soluble phos. phimic acid is slowly formed, which crystallizes in needles, and decomposes on warming with water into tetrametaphosphimic acid and ammonium phosphate. The analysis gave:

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2. ON TRIMETAPHOSPHIMIC ACID AND ITS DECOMPOSITION

PRODUCTS. In the preceding section of this paper I mentioned, by way of pre. liminary notice, that Liebig's chloronitride, PzN;Clo, by appropriate treatment gives an acid, PzN306H6, to which I gave the name trimetaphosphimic acid. The object of the present section is to describe in detail the properties and decomposition products of this, the third member of the metaphosphimic-acid series.

In the preliminary notice a metaphosphimic acid was defined as a metaphosphoric acid (PO,H)n, in which one-third of the oxygen is replaced by an equivalent of imide groups, NH, i. e., (PNO,H2). It was further pointed out that for each acid of this formula, with the exception of the simplest, at least four forms are theoretically possible, two of which are direct substitution products of the corresponding metaphosphoric acid, containing a nucleus consisting of phosphorus atoms anited by oxygen, the other two belonging to a different type, in which the phosphorus atoms are united by nitrogen. This was illustrated by the acid, P,N,08H6, none of the forms of which, it is true, are as yet known with certainty: PO.NH, P(NH).OH

PO.OH

P(OH)2
O< >0
NHANH

N< SN
PÓ.NH
P(NH).OH

POOH

P(OH), (0) (c)

(d) Dimetaphosphory]

Dimetaphosphimic

Diphosphonitrilic amide.

>o

(a)

acid.

acid.

A fifth form might be added:

P.OH

'^
NH 0 0 NH

VA
P.OH

containing at the same time both the metaphosphoric and the metaphosphimic nucleus.

Schiff described a body to which he gave the name phosphaminsäure, formed by acting on phosphorus pentoxide with dry ammonia, and which, according to his analyses, has the formula PNO,H,.? According to Gladstone and Holmes, Schiff's acid is probably a mixture of pyrophosphodiamic and metaphosphoric acids. As Schiff' failed to publish nitrogen determinations for his salts, it still remains a question whether a metaphosphimic acid can be produced in this way.

Gladstone, who was the first to devote much attention to phosphorus chloronitride, obtained from it by the action of aqueous ether and of alcoholic alkalies an acid which he first called deutazophosphoric acid and later pyrophosphodiamic acid, and to which he gave the formula P,N,0,H., regarding it as the diamide of pyrophosphoric acid.

P0(OH)NH,
POOHÍNH

, While I am not prepared to deny positively the correctness of the formula deduced by Gladstone, and to assert that no such acid can be obtained in this way from phosphorus chloronitride, yet the facts as stated by him are capable of another interpretation, namely, that his acid is not the diamide of pyrophosphoric acid, but trimetaphosphimic acid.

It will be seen that

P2N20;H.M'=P2N20,H.M': + H2O,
Pyrophosphodiamate,

the latter being identical in empirical composition with PN,08H2M's+ 1}H20, i. e., a trimetaphosphimate with 1}H20. Hence the latter, if containing this amount of water, might be mistaken for a pyrophosphodiamate. The only salts made by Gladstove directly from the chloride, P,N,C16, were the silver and barium salts; the others were made from a supposed pyrophosphodiamate obtained from phosphorus oxychloride and ammonia, and there is no proof in Gladstone's papers of the identity of the acids from both sources. His figures for the

Ann. Chem. (Liebig), Vol. CIII, 1887, p. 168.

? I havo elsewhere pointed out (Amer. Chem. Jour., Vol. XV, p. 198) that Schiff's acid has been arro. neously described in some of the reference books as amidophosphoric acid, a body which I was the first to obtain.

3 Jour. Chem. Soc. London, (2), Vol. II, pp. 229, 233, 235.

"Quart. Jour. Chem. Soc. London, Vol. III, pp. 135, 354; Ann. Chem. (Liebig), Vol. LXXVI, p. 79; Vol. LXXVII, p. 315; Jour. Chem. Soc. London, [2], Vol. II, p. 231.

Jour. Chem. Soc. London, (2), Vol. VI, p. 69.

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