STOKES.] 
TETRAMETAPHOSPHIMIC ACID. 
123 
precipitate of neutral manganese tetrametaphosphimate; on adding a 
mineral acid this is decomposed, according to the proportion of the 
latter, into acid salt or free acid, or a mixture of both. The acid salt 
forms handsome pinkish rectangular plates, often superposed at various 
angles, and is one of the most characteristic salts obtained. 
Ferric chloride gives no x)recipitate with a cold dilute solution of the 
neutral ammonium salt; on warming a white amorphous precipitate 
forms, which is soluble only on warming with much hydrochloric acid, 
from which solution, on cooling, the free acid separates. 
Tetra-silver tetrametaphosphimate ■, P 4 N 4 8 H 4 Ag4. — If to a cold solu- 
tion of tetrametaphosphimic acid silver nitrate be added the resulting 
precipitate is white, curdy, anil, under the microscope, granular or 
amorphous; formed in the presence of some alcohol it is even flocculent. 
These amorphous precipitates, after drying, slowly change to needles, 
and this occurs at once if they be boiled under water. The salt is 
obtained at once in crystalline form if a slight. excess of silver nitrate 
be added to a hot solution of tetrametaphosphimic acid in 200-300 parts 
water. It requires but a slight excess of silver nitrate to bring about 
complete precipitation, the liberated nitric acid exercising a, scarcely 
perceptible solvent action. Neutral ammonium salt may be used, but 
the addition of a little nitric acid is essential, otherwise the product is 
yellowish from contamination with the 8-atoni silver salt. 
When precipitated hot the salt sometimes consists of thick needles 
with tufts or brushes at each end, sometimes of long pointed plates, 
more rarely of rhombic plates, and in no case are they well formed or 
very characteristic. An acid salt could not be obtained, but the neutral 
salt always shows a slight deficiency of silver. 
The air-dried substance lost nothing at 100° and gave: 
Calculated for 
P 4 N 4 8 H 4 Ag 4 . 
Found. 
1. 
■2. 
3. 
17.04 
4. 
5. 
G. 
p .... 
N-... 
Ag... 
16. G8 
7.55 
58.04 
16.78 
17.04 
16.68 
16.84 
it;. 7i 
7.(11' 
57. 40 
57.06 
56.13 
57. 09 
57.09 
2. 
P 
: Ag = 4 : 3.85. 
3. 
P 
: Ag = 4 : 3.79. 
4. 
P 
: Ag — 4 : 3.94. 
5. 
P 
Ag = 4 : 3.90. 
ii. 
P 
: N : Ag = 4 : 4.02 
3.95. 
Octa-silver tetrametaphosphimate, P,"N".,0 ;; Ag: ; . — Tf an ammoniacal solu- 
tion of a tetrametaphosphimate be added to an excess of silver nitrate, 
a yellowish ilocculent precipitate forms, which is insoluble in ammonium 
nitrate and which does not change on boiling under its mother-liquor 
