on the Vapour of Acids* 291 
1000), I colledled 39 dw. 6 gr. of the volatile acid, of the 
fpecific gravity of 1340, and 130 oz. meafures of dephlogifti- 
cated air of the purefl kind, viz. of the fiandard of 0.15. 
It is eafy in this manner to colled: a great quantity of de- 
phlogifticated air ; hut the principal objection to the procefs is, 
that after ufing a few times, the earthen tubes become tender, 
and too eafily break, efpecially in heating or cooling. It is 
alfo difficult to lute the retort containing the acid and the 
earthen tube. The air produced in this manner is filled with 
the denfeft white cloud imaginable. 
Going through the fame procefs with fpirit of nitre, the 
refult was in all respects limilar, but much more fir iking, the 
produdion of both dephlogifticated air and phlogifticated acid 
vapour being prodigioufly quicker, and more abundant. Ex- 
pending 5 oz. 8 dw. 6gr of lpirit of nitre, 1 colleded 600 oz. 
meafures of very purl dephlogifticated air, being of the ftan- 
dard of o.'2. 1 alfo colleded 1 oz. 7 dw. I4gr. of a greenifh 
acid of nitre, which emitted copious red fumes. All the appa- 
ratus beyond the hot tube was filled with the denfeft red vapour, 
and the water of the trough in which the air was received was 
fo much impregnated with it, that the fmeil was very ftrong ; 
and it fpontaneoufly yielded nitrous air fever.al days, juft as 
water does when impregnated with nitrous vapour. Perceiv- 
ing the e miifion of air from the water, after it had flood fome 
time, I filled a jar containing 30 oz. meafures with it, and 
without any heat it yielded two oz. meafures of the ftrongeft 
nitrous air. 
Taking the fpecific gravity of the acid before and after this 
diftillation, the former was to the latter as 1471 to 1182. 
When the weight of the air produced in this experiment, and 
that of the liquor diftilled, is compared with that of the acid 
7 before 
