120 
CONTRIBUTIONS TO CHEMISTRY AND MINERALOGY 
[ BUI L. 167. 
reaches the theoretical, a portion of the water being taken up in pro- 
ducing intramolecular changes. 
Loss calculated for 2IL 2 10. 22 
(1) Loss after twenty- four hours (weight constant) 9.37 
(2) Loss after seventy-eight hours ( weight constant) 8. 91 
If rapidly heated to 130-140° the loss is still less, and is soon replaced 
by a gain; after thirty hours at this temperature a net increase of 
11.15 per cent, corresponding to somewhat more than 2 molecules H 2 0, 
was observed, which must have come from the atmosphere. The 
product consisted of unchanged acid with ammonium phosphate and 
apparently pyrophosphate. 
Tetrametaphosphimic acid forms colorless needles, either single or in 
radiating groups, and visible without a lens; they appear to consist of 
flat rectangularly terminated prisms. One hundred parts water at 20° 
dissolve 0.04 part crystallized acid; in boiling water it is somewhat 
more soluble, but is insoluble in alcohol. From its saturated aqueous 
solution it is partially precipitated by adding one of the stronger acids, 
and more rapidly if heated; 100 parts by weight of 10 per cent nitric 
acid at 20° dissolve only 0.26 x>art of the crystallized acid, but on 
decomposing its salts in the cold by an excess of acid it frequently dis- 
solves completely and separates out later. Its saturated aqueous solu- 
tion does not coagulate albumen. Boiling alkaline solutions cause no 
evolution of ammonia. Its stability toward acids is illustrated by the 
following: 0.1 gram, dissolved in 200 cubic centimeters water with 8 
cubic centimeters strong nitric and some hydrochloric acid, was evapo- 
rated to dryness on the water bath, whereby a large part was recov- 
ered unchanged; ten minutes' heating would have sufficed for the total 
decomposition of the same quantity of trimetaphosphimic acid. Nitrous 
acid has no perceptible action. 
Di-potassium tetrametaphosphimate, P 4 N 4 8 H G K 2 . — The free acid dis- 
solves easily in cold dilute caustic potash; on strongly acidifying with 
acetic acid the solution remains clear, but on warming the above salt 
is deposited as a heavy, sandy powder, consisting of microscopic thick 
rectangular (quadratic?) prisins with basal planes. It is very difficultly 
soluble even in boiling water. 
The air-dried substance lost nothing at 100° and gave : 
Calculated for 
P 4 N 4 8 H 6 K 2 . 
Found. 
p 
31.61 
19.93 
31.26 
20.05 
K 
flat, obliquely terminated 
P:K = 4:2.03. 
The tetra-potassium salt formed large, 
plates, very soluble, and was not isolated. 
Tetra-sodmm tetrametaphosphimate, P 4 N 4 8 H 4 Na 4 + 2J(?)H 2 0. — The 
acid is suspended in a little water and an excess of dilute caustic soda 
