STOKES.] 
HIGHER METAPH0SP1IIMIC ACIDS. 
149 
Hexambtaphosphimic Acid. 
/POOH.NH.POOH.NH.POOI Lv 
NH< >NH. 
POOH.NH.POOH.NH.POOH X 
This is the lactam of amidopentimidoliexaphosplioric acid, 
/OH 
/POOH.NH.POOH.NH.PO< 
NH< X NH 2 
x POOH.NH.POOII.NII.PO(OH) 2 
It is obtained as sodium salt by saponifying hexaphosphonitrilic chlo- 
ride in ethereal solution by sodium hydroxide in the manner above 
described. In neutral or acid solution it has the lactam form, as shown 
by the composition of the silver salt, but in alkaline solution it'has pre- 
sumably the open form. The free acid, obtained in solution by decom- 
posing the silver salt under water by hydrogen sulphide, has an astrin- 
gent rather than acid taste, and can not be obtained pure in the solid 
form, as it is not precipitated by alcohol, and the solution, on evapo- 
rating, undergoes much decomposition, leaving a gummy residue. 
Sodium hexametaphosjyhimate, P 6 N G 12 II ]S"ao -f 2H 2 0.— The properties 
of this salt are essentially the same as those of the corresponding pen- 
tametaphosphimate. When containing an excess of alkali it is stable, 
but with a deficiency it decomposes more or less rapidly. A salt of 
approximately normal composition can be obtained by adding to the 
solution of a preparation with more than (> atoms of sodium enough 
nitric acid to neutralize the excess and precipitating by alcohol (anal- 
yses 3 and I). In the following table the results are expressed in 
formulas based on the determined ratio P : Na. The samples were dried 
at 100°. 
1 
2 
3 
4 
5 
Ratio P : N : Na. 
P. 
N. 
Na. 
I P fi N»iOi2Hr,. fi r,Nar.35+2HaO 
28.62 
28.55 
28.51 
28.31 
29. 02 
29. 13 
29.02 
29. 16 
31. 05 
30.89 
12.95 
12.96 
13.14 
13.27 
13.14 
13.29 
22.50 
22.45 
22. 80 
22. 63 
21.31 
21. 38 
21.31 
21. 43 
17.70 
17. 60 
6:6.02:6.35 w* *-*****"!- ^ 
iFound 
a t fP«N 8 O w H 8 ^Na 6 .«+2H«0 
6: : 6.461 
j P t; Nr ) 1 . 2 Hr,„7Na,. 9 : i +2H,0 
6:6.04:5.93 ^ 
i P.-N.-Oi H, .,„ Na,..u+2TI.O 
6:6.05:5.91 "" U,J + " 
(PkN.-Oi^Ht 4( ,Na l .ni+2H,0 
b: :4.b0i 
Found . 
