stokes.] TRTMETAPHOSPHIMIC ACID. 105 
Unfortunately, the figures do not admit of a positive decision as to 
the formula, but the extreme instability of the salt, as compared with 
the others, may indicate an acid of different nature from trimetaphos- 
phimic acid. 
If this salt be allowed to stand for a day or two under pure water, it 
is converted into a mixture of tertiary silver trimetaphosphimate and a 
yellow crystalline salt with 6 atoms silver. 
3P 3 N 3 7 H 4 Ag 4 = P 3 N30 7 H 2 Ag ri + 2P3N 3 6 H 3 Ag3 + 2H 2 0. 
The same change occurs rapidly on boiling. Whatever may be the 
nature of the salt, this change is doubtless due to the tendency of the 
silver to wander to the nitrogen j silver nitrate, by opposing dissocia- 
tion, prevents alteration. 
Salts with 6 atoms of silver, P 3 N 3 () 6 Ag 6 and perhaps P 3 N 3 7 H 2 Ag„ 
also. — Equally unsatisfactory analytical results are given by the salts 
with 6 atoms of silver. The figures indicate the tendency to formation 
of salts with the ratio P: Ag=3:6, but the actual ratio only approxi- 
mates to this, and it is impossible on the basis of the analyses alone to 
decide which of the formulas P 3 N 3 6 Ag 6 and P :i N 3 7 H 2 Ag c should be 
adopted in most cases. After many experiments I have been com- 
pelled to abandon for the present the attempt to obtain these sub- 
stances in entirely satisfactory condition, and give the figures as 
actually obtained. 1 
If sodium trimetaphosphimate be added to an excess of an amino- 
niacal solution of silver nitrate, 2 or of a solution of silver oxide in 
ammonium nitrate, 3 a portion of the trimetaphosphimic acid is pre- 
cipitated as a pure white voluminous and amorphous body, which, 
as analysis shows, contains approximately 6 atoms of silver. The pre- 
cipitation is very incomplete, especially when ammoniacal silver nitrate 
is used, but in this case the substance contains very nearly 6* atoms 
of silver, while if the silver oxide solution be employed the percentage of 
silver is considerably too low. 4 Heated under the mother liquor it 
becomes yellowish, and becomes white again on cooling. After washing 
out (whereby it becomes yellowish) it dissolves quite readily in strong 
ammonium nitrate solution, but if boiled with less of the same, or less 
rapidly if heated with water alone, it is quickly converted into a heavy 
pulverulent substance. This, if highly magnified, is seen to consist of 
spherules or indistinct prisms, and has a color varying from orange to 
3eep orange-red, usually the latter. This salt likewise contains 6* 
itoms of silver. The transformation is prevented by any silver nitrate 
n the solution, unless the effect of this is neutralized by a large quan- 
tity of ammonium nitrate. 
!See p. 146 of this bulletin for an explanation of these difficult^ 8. 
2 Prepared by adding ammonia to silver nitrate solution till the brown precipitate just redissolves. 
3 Three grams silver oxide, 10 grams ammonium nitrate, and 50 cubic centimeters water. 
4 The nitrate, on evaporation over sulphuric acid, deposits an imperfectly crystalline substance, at 
rst white, then yellow, which is probably identical with the yellow salt referred to below. 
