C 231 J 
XV. On a Method of analyzing Stones containing fixed Alkali, by 
Means of the Boracic Acid. By Humphry Davy, Esq. F. R.. S. 
Professor of Chemistry in the Royal Institution . 
Read May 16, 1805. 
I have found the boracic acid a very useful substance for 
bringing the constituent parts of stones containing a fixed alkali 
into solution. 
Its attraction for the different simple earths is considerable 
at the heat of ignition, but the compounds that it forms with 
them are easily decomposed by the mineral acids dissolved in 
[ water, and it is on this circumstance that the method of analysis 
is founded. 
The processes are very simple. 
100 grains of the stone to be examined in very fine powder, 
must be fused for about half an hour, at a strong red heat, in 
a crucible of platina or silver, with 200 grains of boracic acid. 
An ounce and half of nitric acid, diluted with seven or eight 
times its quantity of water, must be digested upon the fused 
mass till the whole is decomposed. 
The fluid must be evaporated till its quantity is reduced to 
an ounce and half or two ounces. 
If the stone contain silex, this earth will be separated in the 
process of solution and evaporation ; and it must be collected 
upon a filter, and washed with distilled water till the boracic 
acid and all the saline matter is separated from it. 
