STOKES.] 
TRIMETAPHOSPHIMIC ACID. 
09 
owing to the development of but one terminal plane, in winch case the 
terminal angles are respectively rather more and rather less than 45°. 
In general properties it resembles the <r-salt, which it gives when 
repreeipitated from cold solution ; whether the difference consists merely 
in the amount of crystal water, or whether it is a chemically distinct 
body can not be decided at present. 
Tetra-sodium salt (sodium amidodiimidotriphosphate), P 3 N ;i 7 H 4 Na4-t- 
H 2 C). — As pointed out in the introduction, this is best regarded as the 
neutral salt of an open chain acid,' 
PO.O< NH - 1>0 <NH, 
x NH.PO(OH), 
of which trimetaphosphimic acid is the inner anhydride. As positive 
proof of this can not be adduced at present, I have preferred to place 
it among the trimetaphosphimates. 
On dissolving sodium trimetaphosphimate in an excess of caustic 
soda, concentrating and allowing to cool, the salt crystallizes in long 
brittle needles (analysis 1). On adding alcohol to a caustic soda solu 
tion of sodium trimetaphosphimate (which need not have been heated), 
it is thrown out as a sirup which crystallizes, slowjy if left to itself, 
at once on adding a fragment of previously prepared salt, to a mass of 
delicate colorless needles (analysis 2). These must be washed with 
alcohol containing a little caustic soda in solution, strongly pressed 
out and dried out of contact with carbon dioxide. It contains a huge 
amount of crystal water, which it loses, with the exception of the last 
molecule, on drying in vacuo ; the exact amount could not be determined. 
The substance dried in vacuo lost nothing at 100° and gave: 
Calculated for 
P 3 N 3 7 H 4 Na 4 
+ H 2 0. 
Found. 
1. 
2. 
p 
25.76 
11. 66 
25.51 
25.34 
25. 60 
11.96 
25. 76 
N 
Na 
25.60 
1. P :Na = 3 : 4.08. 
2. P : N : Na = 3 : 1.09 : 4.06. 
This salt is very unstable, being decomposed even in the solid state 
y carbon dioxide. From its cold aqueous solution alcohol precipitates 
mixture of unchanged salt and a-sodium trimetaphosphimate, a few 
eprecipitations converting it completely into the latter and free alkali. 
ts behavior toward silver nitrate is described under the silver trimeta- 
hosphimates. 
Salts with less than 3 or more than 4 atoms of sodium could not be 
btained. 
