HIGHER MHTAPIIOSPHIMIC ACIDS. 
151 
in the manner described above. The yield is 30 per cent of that 
required by 
P,;N„Oi -jllia + 4H 2 = P.N.OsHs + 2NH.H-2PO,. 
After purifying, it was converted into the silver salt, which gave: 
Calculated for 
P 4 N 4 8 lI 4 Ag 4 . 
Found. 
p 
16. 68 
7.55 
58. 03 
16.63 
7.50 
57. 58 
N 
As 
P :N : Ag=4 : 3.99 : 3.98. 
Comparison of the crystals of free acid and of the acid and neutral 
ammonium salts, acid potassium salt, neutral sodium salt, and silver 
salt with similar preparations made from tetraphosphonitrilic chloride 
showed that they were identical. 
The decomposition products were not further studied. 
Amidoheximidoheptaphosphouic Acid, P 7 N 7 0i 5 H lt ;. 
The saponification of heptaphosphonitrilic chloride is effected in the 
usual manner with sodium hydroxide. As before pointed out, this acid 
does not give the lactam, heptametaphosphimic acid, even in acid 
solution, the silver salt having the composition of a salt of the open- 
chain acid. 
Sodium salt. — The properties of this salt are similar to those of 
sodium penta- and hexainetaphosphimate. Dried in vacuo and at 100°, 
it gave : 
Calculated for 
P.N 7 16 H 8 . 67 Na 7 . 4S + 2U ,0. 
Found. 
28.31 
22.31 
p 
28. 16 
22. 19 
Na 
P :Na= 7 : 7.43. 
Silver salt, P 7 N 7 Oi 5 H 9 Ag 7 . — To obtain a salt of normal composition, 
L gram sodium salt is dissolved in 50 cubic centimeters water, enough 
ttitric acid is added to form a salt with 6.85 atoms of sodium, and pre- 
cipitated by 50 cubic centimeters one-fifth normal silver nitrate. More 
sodium or silver nitrate gives a salt richer in silver. The salt forms a 
vhite semigelatinous precipitate, which dries in vacuo to translucent 
brittle lumps, which were pulverized, dried again in vacuo and then 
sarefully to constant weight at 100°. 
