90 CONTRIBUTIONS TO CHEMISTRY AND MINERALOGY. [bull. 167. 
A fifth form might be added: 
P.OH 
NH NH 
P.OH 
containing at the same time both the metaphosphoric and the meta- 
phosphimic nucleus. 
Schiff 1 described a body to which he gave the name phosphamin- 
sreure, formed by acting on phosphorus peutoxide with dry ammonia, 
and which, according to his analyses, has the formula PN0 2 H 2 . 2 
According to Gladstone and Holmes,' Schiff's acid is probably a mix- 
ture of pyrophosphodiamic and metaphosphoric acids. As Schiff failed 
to publish nitrogen determinations for his salts, it still remains a ques- 
tion 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 4 an acid which he first called deutazophosphoric acid 
and later pyrophosphodiamic acid, and to which he gave the formula 
P 2 N 2 5 H 6 , regarding it as the diamide of pyrophosphoric acid. 5 
0< 
PO(OH)NH 2 
P0(0H)NH 2 ' 
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 
P 2 N 2 5 H 4 M' 2 = P 2 N 2 4 H 2 M' 2 + H 2 0, 
Pyrophosphodiamate, 
the latter being identical in empirical composition with P 3 N 3 6 H 3 M' 3 4- 
1£H 2 G, i. e., a trimetaphosphimate with 1£H 2 0. Hence the latter, if 
containing this amount of water, might be mistaken for a pyrophos- 
phodiamate. The only salts made by Gladstone directly from the 
chloride, P 3 N 3 C1 6 , 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. Chera. (Liebig), Vol. CIII, 1887, p. 168. 
2 I have elsewhere pointed out (Amer. Chem. Jour., Vol. XV, p. 198) that Setoff's acid has been erro. 
ueously 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. Ill, pp. 135, 354; Ann. Chem. (Liebig), Vol. LXXVI, p. 79; 
Vol. LXXVII,p.315; Jour. Chem. Soc. London, [2], Vol. II, p. 231. 
6 Jour. Chem. Soc. London, [2], Vol. VI, p. 69. 
