312 Heinrich Rose. 
ifferent, isomeri e e pointed out that the change is 
often indicated by momentary incandescence, and by an altera- 
tion in the specific gravity. ‘The passage from the one state to 
transition is attended with no perceptible disengagement of light, 
and the acid which has then passed into the insoluble modifica- 
tion shows no phosphorescence on ignition. ‘I'he phenomenon 
is of the same nature as the incandescence of the ammonlo- 
phosphate of magnesia in becoming pyrophosphate, and probably 
also of the oxalates when they are converted by heat into carbon- 
ates. In all these cases a change in the intimate structure of the 
substance is produced. The disengagement of light is sometimes, 
as in gadolinite, accompanied by evolution of heat, and diminu 
tion of the specific heat of the substance, which it has been sup- 
posed might be its explanation; but in other cases no heat can 
he emission of light during crystallization was investigated, 
and was shown to occur when a body which is destitute of all 
of all 
