140 CONTRIBUTIONS TO CHEMISTRY AND MINERALOGY. [bull. 167. 
is most tenaciously held, while the term is applied to the acids as indi- 
cating the difficulty with which the ring is broken open. In the one 
case, the series consists of polymers of — PC1 2 = N — and in the other 
of — POOH — NH — , and the two series can not therefore be considered 
analogous in a stereochemical sense. 
Only tri- and tetrametaphosphimic acids give characteristic salts. 
The salts of the acids with 5, 6, and 7 atoms of phosphorus are totally 
devoid of crystallizing power, the alkaline salts being precipitated 
from aqueous solution by alcohol as sirups, which can easily be con- 
verted into the solid form by dehydration with absolute alcohol, but 
which are still wholly amorphous. The tendency to diminished acidity 
of unneutralized hydroxyls, well known in the case of orthophosphoric 
acid, is here apparent, and to an increasing extent as we rise in the 
series. Trimetaphosphimic acid forms a salt with 3 atoms of sodium 
which has neutral reaction and is not decomposed by strong acetic 
acid; tetrametaphosphimic acid readily gives salts with 2 and 4 atoms 
of sodium. The 5 atom sodium salt of pentametaphosphimic acid is 
strongly alkaline and shows a tendency to hydrolytic dissociation, and 
the same tendency is still more marked in the higher acids. Owing to 
this and to their amorphous nature it is impossible to obtain salts of 
definite composition from any but the first two acids unless certain 
conditions are rigidly adhered to. Qualitative differences between the 
analogous salts of the higher acids are almost wanting, and only a 
quantitative study and a knowledge of their derivation serve to dis- 
tinguish them. As with other phosphorus-nitrogen acids, no ammonia 
is evolved on boiling with alkalies. 
Amides of the metaphosphimic acids. — Gerhardt 1 has described, under 
the name " phosphatide," a body of the empirical composition PN 2 OH :! , 
which he obtained by action of ammonia and water on phosphorus 
KH 
pentachloride and to which he gave the formula PO^ . This cor- 
responds to the amide of a metaphosphimic acid, but its properties 
indicate that it is probably a substance of high molecular weight. I 
have attempted to obtain amides of the first three metaphosphimic 
acids by acting on the corresponding chloronitrides with gaseous or 
strong aqueous ammonia. The efforts were but partially successful. 
The P:N ratio is sometimes rather higher, sometimes rather lower, 
than is required by the formula (PN 2 OH :i ) u . They have none of the 
properties of Gerhardt's phosphamide, but are extremely soluble in 
water, uncrystallizable, and unstable, and have weakly acid properties, 
forming alkali and silver salts, which, however, are of very variable 
composition and of ill-defined properties. Like the metaphosphimic 
acids, they give off no ammonia on boiling with alkali, but are easily 
decomposed on treatment with acids. 
Ann. Chim.Phys. [3], Vol. XVIII, p. 188. 
