160 Mr. Davy's Account of some analytical Experiments 
The loss I am inclined to attribute to some fluid remaining 
in the stone after the process of distillation ; for I have found, 
from several experiments, that a red heat is not sufficient to 
expel all the matter capable of being volatilized, and that the 
full effect can only be produced by a strong white heat. 
Fifty grains of a very transparent part of the fossil, by being 
exposed in a red heat for fifteen minutes, lost 13 grains; but 
when they were heated to whiteness, the deficiency amounted 
to 15 grains, and the case was similar in other trials. 
Different specimens of the fossil were examined with great 
care, for the purpose of ascertaining whether any minute por- 
tion of fixed alkali existed in them ; but no indications of this 
substance could be observed ; the processes were conducted 
by means of solution of the unaltered fossil in nitric acid ; the 
earths and oxides were precipitated from the solution by being 
boiled with carbonate of ammonia ; and after their separation, 
the fluid was evaporated to dryness, and the nitrate of ammonia 
decomposed by heat, when no residuum occurred. 
A comparative analysis of 30 grains of a very pellucid speci- 
men was made by solution in lixivium of potash. This specimen 
lost 8 grains by long continued ignition, after which it easily 
dissolved in the lixivium by heat, leaving a residuum of a 
quarter of a grain only, which was red oxide of iron. The pre- 
cipitate from the solution of potash, made by means of muriate 
of ammonia, weighed, when properly treated, 21 grains. 
Several specimens were distilled in the manner above de- 
scribed, and in all cases the water collected had similar proper- 
ties. The only test by which the presence of acid matter in 
k could be detected, was litmus paper ; and in some cases the 
effect upon this substance was barely perceptible. 
