384 Dr. Prout’s experiments on the changes which take place 
tity of potash and soda,* and carbonates of potash and soda 
present. Finally, the proportion of the earthy phosphates 
to one another was determined, and the quantities of the bases 
and acid obtained by calculation. 
The yelk of the egg is exceedingly difficult of combustion ; 
and indeed without proper precautions cannot be burnt at all, 
on account of the large quantity of phosphorus it contains ; 
which, by undergoing a partial combustion, forms a glassy 
coating that effectually excludes the contact of the air from 
the coal, and prevents its farther combustion. After a va- 
riety of attempts, the following were the two methods em- 
ployed. The yelk of an egg which had been boiled hard, 
and dried by exposure to the air, was rubbed in a mortar 
with a quantity of bicarbonate of potash. The mixture was 
then Introduced into a platina crucible and exposed to a 
strong red heat, till the flame had ceased to escape from a 
small hole in the lid. The crucible being now removed from 
the fire, its contents, when cold, were again pulverised in a 
mortar with nitre. This mixture was then introduced a little 
at a time into the covered crucible till the whole was burnt. 
To the residuum distilled water was added, which of course 
took up every thing but the earthy phosphates, which were 
separated and weighed, while the alkaline solution, like that 
before mentioned obtained from the albumen, was submitted 
to the action of the appropriate re-agents, and thus the quan- 
tities of the different acids present ascertained. In this man- 
ner every thing was determined, except the proportion of 
alkaline matter present ; and to ascertain this, other experi- 
* The quantity of soda equivalent to the sodium in union with the chlorine, was 
determined by calculation. 
