98 
CONTRIBUTIONS TO CHEMISTRY AND MINERALOGY. 
[BULL. 167. 
The angle a, measured roughly under the microscope, is about 130°. 
No other faces are ever observed, and D is frequently lacking, giving 
the form shown in fig. 2, which is often seen to be elongated in the 
direction of any one of the axes. They are especially well developed 
when slowly thrown down by acetic acid and alcohol from alkaline 
solution. When formed by rapid addition of alcohol in large excess 
they tend to elongation in the direction of the principal axis, being 
often acicular, often long, flat prisms with imperfectly developed ends. 
At 20°, 100 parts water dissolve 18.3 parts; in hot water it is much 
more soluble, and from its hot solution it crystallizes but slowly; the 
larger crystals dissolve in hot water with a crepitating sound. The 
reaction toward litmus is neutral. On rapidly heating the dry salt it 
gives off water and later ammonia, and fuses to a clear glass. It is but 
slowly decomposed by boiling with water; after three hours heating 
traces of phosphoric and imidodiphosphoric acid were shown by mag- 
nesia mixture. Alkalies do not cause the evolution of any appreciable 
quantity of ammonia, even when hot; apparently, however, their very 
long-continued action is attended with decomposition. 
ft- Sodium trimetaphosphimate, P 3 N 3 6 H3Na3-|-H20. — This form is de- 
posited when the solution has a temperature of 80° or higher. It was 
obtained — 
(1) By boiling the solid «-salt under a strong solution of sodium 
nitrite (analysis 1). 
(2) By slowly adding boiling alcohol to a boiling solution of the «-salt 
(analysis 2). 
(3) By pouring a boiling solution of the tr-salt into a boiling 25 per 
cent solution of sodium acetate. 
Doubtless other sodium salts would serve equally well, provided their 
hot solutions are sufficiently strong to throw it out. 
The salt lost nothing at 100° and gave: 
Calculated for 
P3N 3 6 H 3 Na3 
+ H 2 0. 
Found. 
1. 
2. 
p 
28.97 
13. 11 
21. 51 
28.31 
28. 97 
13.08 
21.19 
1 
N 
Na 
21.86 
1. p 
2. P 
Na = 3 
N : Na : 
3.12. 
= 3 : 2.99 : 2.90. 
This modification of the sodium salt forms needles, which, under the 
microscope, are seen to consist of flat prisms terminating in points; the 
terminal angles are of two kinds, one rather more, the other rather less 
than 90°; frequently both of these may be observed at opposite ends 
of the same crystal. Often, too, the crystals are cut off obliquely, 
