66 Dr Froufs Experiments on the Changes which take place 
The shells of eggs have been analysed by Vauquelin and 
Merat Guillotp but these chemists seem to have over-rated the 
quantity of animal matter, and of phosphate of lime, contained 
in them. When shells, which had been dried in vacuo at 212°, 
were dissolved in dilute muriatic acid, the quantity of animal 
matter obtained was only about % per cent ., while the quantity 
of phosphates of lime and of magnesia never amounted to 
quite 1 per cent. ; the rest was carbonate of lime, mixed with 
a little carbonate of magnesia. When burnt, egg-shells, as 
Vauquelin has observed, yield traces of sulphur and iron. 
The memhrana putaminis , on the supposition that the origi- 
nal weight of the egg is 1000 grs., weighs, when dried in vacuo 
at 212°, about 2.35 grains ; and, on being burnt, yields traces of 
phosphate of lime. 
Saline Contents of the recent Egg . 
Ii may here be premised generally, that all the results of the 
following analyses were obtained by combustion ; and that the 
observations are to be understood as applicable to the whole of 
the experiments subsequently related in this inquiry. 
The albumen burns with difficulty, unless care be taken to 
remove the saline matter by frequent washings ; but if this 
point be attended to, the whole of the carbonaceous matter 
may be burnt off even in a covered crucible. In the subse- 
quent experiments, the saline and earthy matters were removed 
from the crucible after combustion by distilled water ; a little 
ammonia was then added, and the whole permitted to remain 
at rest for twenty-four hours. The clear solution containing the 
alkaline salts was now carefully poured off, and the insoluble re- 
siduum, consisting of the phosphate of lime and triple phos- 
phate of magnesia and ammonia, after being washed with dis- 
tilled water, was dried and weighed. The alkaline solution, 
together with the washings of the earthy phosphates, were then 
evaporated to dryness, and exposed to a low red heat ; and the 
weight of the saline residuum being accurately noticed, the 
whole was again dissolved in distilled water. A few drops of 
nitric acid being now added to neutralize the excess of alkali 
present, nitrate of barytes was dropped into the solution as long 
as any precipitate fell. The precipitate was obtained by de- 
