stokes.] HIGHER METAPHOSPHIMIC ACIDS. 
For analysis the salts were dried at 100°. 
143 
Calculated for 
P 6 N 5 O 10 H 6 Na 5 -f2H 2 O. 
Found. 
1. 
2. 
3. 
4. 
p 
28.64 
12.96 
21.27 
28.23 
12. 90 
22.74 
28.24 
12.86 
22.64 
29.10 
13.29 
21.54 
29.13 
13.22 
20.77 
N 
Na 
1 and 2 were precipitated directly from alkaline solution. 
1. P:N:Na=5:5.02:5.42. 
2. P:N:Na=5:5.03:5.40. 
3 and 4 were precipitated from a solution neutralized with acetic acid with 
phenolphthalein as indicator. 
3. P:N:Na = 5 
4. P:N:Na = 5 
"•5.03:4.75. 
5.02 : 4.80. 
The tetra-sodium salt, P5N r) 1 oH 5 .Na 1 H+2H 2 0, is obtained by dissolv- 
ing the crude salt in water with its own weight of 80 per cent acetic 
acid and precipitating twice by alcohol. It resembles the normal salt, 
but has neutral reaction. 
It gave after drying at 100°: 
Calculated for 
P 6 N 5 O I0 H 5 Na 4 H+2H 2 0. 
Found. 
p 
29.85 
17.74 
30.02 
17.71 
Na 
P: Na = 5: 3.97. 
Salts with still less alkali can be obtained by precipitating the crude 
salt by alcohol from a nitric acid solution. This precipitate is viscous 
rather than sirupy, as with the salts with 4 and 5 atoms of sodium. 
Salts with 5 or more atoms of sodium can be kept indefinitely without 
alteration and do not evolve ammonia with alkalies, but those with less 
gradually decompose. 
Barium salt. — A solution of the sodium salt gives, with barium chlo- 
ride, a voluminous precipitate of unknown composition, insoluble in 
water and acetic acid. 
Magnesium salts. — Pentametaphosphimic acid forms several salts with 
magnesium alone, as well as double salts with magnesium and other 
tnetals. 
A solution of the sodium salt, strongly acidified with acetic acid, 
gives, with magnesium salts, a voluminous, amorphous precipitate, 
nearly insoluble in water and but slightly more soluble in strong acetic 
icid. The composition of this, after drying at 100°, approximates to 
r 5 N 5 O 10 H 5 .Mg 2 H+5LJ 2 O. 
