100 
CONTRIBUTIONS TO CHEMISTRY AND MINERALOGY. [bull. 167. 
Potassium trimetaphosphimate, P^OgHoK:.. — A solution of this salt 
was obtained by decomposing the barium salt with potassium sulphate; 
on evaporation a transparent, glassy mass resulted. Alcohol precipi- 
tated it as a sirup, which on repeated treatment with absolute alcohol 
was converted into indistinct crystals. It was not further examined. 
Ammonium trimetaphosphimate, P 3 N 3 6 H3(NH 4 )3 -f- H 2 0. — A solution 
of this salt was obtained by double decomposition from the barium and 
silver salts and by neutralizing the free acid with ammonia. It loses 
ammonia on evaporation and leaves- a transparent amorphous residue. 
Its solution, treated with alcohol, gives a deposit of large and beautiful 
pearly scales, which are characteristic. As these form even in the 
presence of a large excess of ammonia it appears that a body analogous 
to the tetra-sodium salt can not be thus formed. 
The air-dried substance gave: 
Calculated for 
P 3 N 3 6 H 3 (NH 4 ), 
+ H 2 0. 
Found. 
p 
30.38 
27.50 
1 
30.19 
27.03 
N 
Magnesium trimetaphosphimate, (PsN^OeH^^Mg^?). — Strong solutions 
of sodium trimetaphosphimate and magnesium chloride give no precip- 
itate, even on boiling. A solution of the magnesium salt may be 
obtained by double decomposition. From this alcohol throws down an 
amorphous fioceulent precipitate and it leaves a soluble transparent 
residue on evaporating. Ou boiling the solution is slowly decomposed. 
A mixture of a not too dilute solution of sodium salt with an excess 
of a strong solution of magnesium acetate remains clear, but is precip- 
itated by acetic acid ; on adding a little water this precipitate redis- 
solves, reappears on heating, and redissolves on cooling. The nature 
of these precipitates has not been investigated. With more water the 
solution remains clear on short boiling, but on continued heating a 
crystalline precipitate forms which examination shows to consist of 
magnesium pyrophosphate and imidodiphosphate, orthophosphoric acid 
remaining in solution. 
The fact that trimetaphosphimic acid is not precipitated in the cold 
by ammoniacal magnesia mixture affords a valuable means of separat- 
ing it from some of its decomposition products. 
Barium trimetaphosphimates. — Much time was spent in studying 
these salts, until it was found that they are devoid of characteristic 
properties, and that they are of exceedingly varying composition. Both 
neutral and basic salts exist, and there is a strong tendency to form 
double salts. The tendency to form complex salts is so strong that 
when barium nitrate, chloride, or acetate is used as the precipitant, the 
product is invariably contaminated by these. It has proved impos- 
