77 
on the Nature of certain Bodies . 
gene, there was a most intense ignition before the tempera- 
ture was nearly raised to the red heat ; the potassium entered 
into vivid inflammation, where it was in contact with the 
boracic acid. When this acid had been heated to whiteness, 
before it was introduced into the tube, and powdered and 
made use of whilst yet warm, the quantity of gas given out 
in the operation did not exceed twice the volume of the acid, 
and was hydrogene. 
I could only use twelve or fourteen grains of each of the 
two substances in this mode of conducting the experiment ; 
for when larger quantities were employed, the glass tube 
always ran into fusion from the intensity of the heat produced 
during the action. 
When the film of naphtha had not been carefully removed 
from the potassium, the mass appeared black throughout ; but 
when this had been the case, the colour was of a dark olive- 
brown. 
In several experiments, in which I used equal parts of the 
acid and metal, I found that there was always a great quantity 
of the former in the residuum, and 'by various trials, I ascer- 
tained that twenty grains of potassium had their inflammabi- 
lity entirely destroyed by about eight grains of boracic acid. 
For collecting considerable portions of the matters formed 
in the process, I used metallic tubes furnished with stop-cocks, 
and exhausted after being filled with hydrogene. 
When tubes of brass or copper were employed, the heat 
was only raised to a dull red ; but when iron tubes were 
used, it was pushed to whiteness. In all cases the acid was 
decomposed, and the products were scarcely different. 
When the result was taken out of a tube of brass or copper. 
