Chemistry and Physics. 417 
without difficulty. Light accelerates its decomposition; as does 
also heat, though even at 43° it is not very rapid. This change 
into nitrogen tetroxide and oxide is endothermic, and is not re- 
versible-— Bull. Soc. Ch., I, xx, 53, Jan., 1874. G F. B 
- On Ammonium nitrite.—This salt is rarely seen in the dry 
form, and hence has been but little studied. Brrraenot, having 
occasion to prepare it for his thermochemical researches, gives the 
that when agitated they evolve gas like champagne. Ammonium 
nitrite may be formed synthetically by mixing together nitrogen 
oxide, ammonia and oxygen. ‘The solid nitrite condenses on 
Tl, xx, 55, Jan., 1874. G. F. B. 
5. Mechanical Equivalent of Heat.—H. Serrano Y. Fatt- 
GATt has for the first time determined the relation which subsists 
between the work expended to turn the disk of a Ramsden elec- 
trical machine and the electro-static decompositions 
The following are, in brief, the processes employed, and the re- 
ined 
lated work, Ist, the work equivalen 
the Weights at the end of their fall, and 2nd, the 
by the friction of the strings against the han 
pulleys 
work consumed 
dle and in the 
a On the other hand, he estimated as exactly as possible the 7 
eveloped by the cushions; first, by employing a good mercu 
