. 
Chemistry and Phisies. 141 
amorphous mercuric iodide changes to the heavier red crystalline 
variety, amorphous arsenic becomes the heavier crystalline arsenic. 
Hence Spring enunciates the following law: Pressure can pro- 
€8., XV1, 2723, Nov., 1883. G. F. B, 
2. On nitrogen selenide.—BeRTHELOT and VrierLiE have exam- 
NSe (93 grams)=N +Se:42°9 and 42°4 calories, or, as a mean 
42°6; or 42-3 calories at constant pressure. Nitrogen selenide 
therefore is formed with absorption of heat (—42°3 calories), like 
ts congeners nitrogen sulphide (—31-9 calories) and nitrogen 
dioxide (—21-6 calories); the heat absorbed increasing with the 
chemical equivalent, following the ordinary law.—Buli. Soe. 
him., Il, x1, 420, Nov., 1883. G. F. B 
n Hyponitrous acid and silver apes RANE Si 3° 
and Ocizr have examined the hyponitrous acid of Divers and 
also its silver sa latter was pre y the process of 
the dis overer, dissolved in very dilute nitric acid and re ipi- 
tat ing the salt to undergo decomposition 
ture and in the dark. Thus prepared it contained a trace of water 
ut no reduced silver. On analysis it gave a slightly different 
formula from that ordinarily accepted, viz: Ag,N,O,. The acid 
would then be H,N,O,. The authors believe that this formula” 
accords better with the results obtained by a quantitative study 
of <3 reactions and with the existence of the acid salts discove 
all the nitrogen not being evolved in this gas, but a part going to 
form nitric acid thus : | 
(H,N,0,),=(N,0), + (HNO3)2+(H29);- 
