on the Newry pitch-stone, &c. 31 g 
nese ; and in the liquor from which the sulphate of lime was 
extracted, there was no sulphate of magnesia. 
The alumina boiled in sulphuric acid and mixed with sul- 
phate of potash was converted into alum, leaving nothing in 
solution. 
The first thing which caught my attention in the course of 
this process, was the appearance of a black insoluble matter 
in the muriatic solution from which the silica had been sepa- 
rated. As it evaporated with considerable rapidity, in conse- 
quence of the great heat of the sand bath, a rim was left from 
time to time on the surface of the pan of dry salt, which, 
from being orange, became white, and shortly after a black 
powder used to separate from it, fall to the bottom of the pan, 
and remain undissolved. 
This I at first suspected to be oxide of manganese ; but 
having collected it, I found that it was insoluble in acids, and 
that it burned away at a red heat. 
I then conceived that some carbon had accidentally got 
into the liquor ; but as the same phenomena recurred with 
every experiment, and I repeated my analysis many times, I 
became convinced that it belonged to the stone. Other circum- 
stances, however, put it out of doubt. 
To obtain the alkalies, if any existed in the stone, I pursued 
each of the methods usually recommended ; that invented by 
Rose, and practised by Klaproth ; that of Sir Humphry 
Davy ; the new process by Ceruse ; and the action of acids 
on the stone ; by the last of which I finally abided. 
Klaproth mixed 100 grains of the pulverised stone with 
300 of nitrate of barytes, ignited them in a porcelain cru- 
cible, and neutralised the mass with muriatic acid, which he 
