STOKES.] 
TETRAMETAPHOSPHIMTC ACID. 
121 
added, whereby complete solution occurs. The separation of the neu- 
tral salt soon begins in the form of obliquely terminated flat prisms, 
sometimes single, sometimes in twins or quadruplets ; the filtrate de- 
posits more on heating, but in imperfect forms, broader at one end 
than at the other. Sometimes nothing separates from the alkaline 
solution until it is heated. On the contrary, strong caustic soda con- 
verts the solid acid in the salt without dissolving it. The salt is rather 
difficultly soluble in cold, quite easily in hot, water, but much less sol- 
uble in the presence of an excess of alkali, and the latter throws it- 
down from its saturated aqueous solution. Sodium carbonate gives 
the same salt. 
The substance, pressed out without washing and dried in vacuo, lost 
nothing at 100° and gave: 
■ 
* Calculated for 
P 4 N 4 fi H 4 Na 4 
-t-2JH,0. 
Found. 
1 
2 
p 
27.62 
20.50 
27.61 
21.23 
27.71 
20.80 
Na 
1. P:Na 
2. P:Na 
4:4.14. 
4:4.05. 
Alcohol precipitates this salt in a slimy form, which filters with dif- 
ficulty. 
A solution of the tetra-sodium salt, strongly acidified with acetic 
acid, gave a deposit of granules, £>robably the acid salt. A salt with 
more than 4 atoms of sodium 1 was not observed. 
Tetra- ammonium tetrametaphosphimate, P 4 N 4 8 H 4 (NH4) 4 +4H 2 0. — 
Strong ammonia converts tetrametaphosphimic acid into this salt with- 
out dissolving it; from its solution in weaker ammonia it is precipitated 
by alcohol. It usually forms well-developed, flat, monoclinic prisms with 
pinakoid and basal planes, the base being occasionally replaced by a 
set of many small planes. It is easily soluble in water, but difficultly in 
strong ammonia. Its solution undergoes partial decomposition into acid 
salt on evaporating. It loses nothing in vacuo, and analysis gave: 
Calculate^ for 
P 4 N 4 8 (NH 4 ) 4 
+4H 4 0. 
• 
Found. 
l 
2 
3 
p .. 
27.19 
24.61 
6.15 
27.12 
24.74 
27.25 
N 
24. (Hi 
H 
5. 94 
1. P:N 
3. P:N 
4:8.12. 
4:8. 
Compare the behavior of trimetaphosphimic acid toward excess of alkali. 
