232 Mr. Davy on a Method of analysing Stones , &c. 
The fluid, mixed with the water that has passed through the 
filter, must be evaporated, till it is reduced to a ‘convenient 
quantity, such as that of half a pint ; when it must be saturated 
with carbonate of ammonia, and boiled with an excess of this 
salt, till all the materials that it contains, capable of being pre- 
cipitated, have fallen to the bottom of the vessel. 
The solution must then be separated by the filter, and the 
earths and metallic oxides retained. 
It must be mixed with nitric acid till it tastes strongly sour, 
and evaporated till the boracic acid appears free. 
The fluid must be passed through the filter, and subjected 
to evaporation till it becomes dry ; when, by exposure to a 
heat equal to 450° Fahrenheit, the nitrate of ammonia will be 
decomposed, and the nitrate of potash or soda will remain in 
the vessel. 
It will be unnecessary for me to describe minutely the 
method of obtaining the remaining earths and metallic oxides 
free from each other, as I have used the common processes. 
I have separated the alumine by solution of potash, the lime by 
sulphuric acid, the oxide of iron by succinate of ammonia, the 
manganese by hydrosulphuret of potash, and the magnesia by 
