ON PLUMBAGO 181 



evident that, during the ustulation and distillation of plum- 

 bago, no sublimate or anything like a sublimate is driven off. 



SECTION VI. 



There was one circumstance observable which deserves 

 the greatest attention, viz. the aerial acid which was expelled 

 during the saturation of the fixed alkali (Sec. in. (d)). I 

 was led by this to mix 15 grs. of levigated plumbago with 

 8 scruples of nitre, and to put it into a small retort of thick 

 glass. A large empty bladder was adapted to the retort, 

 and it was placed upon live coals. As soon as the nitre 

 entered into fusion, the mass in the retort took fire, and the 

 bladder became distended. After the whole was cooled, I 

 detached the bladder from the neck of the retort, and found 

 that the air contained in it occupied as much room as 36 oz. 

 of water. Lime-water absorbed one-third of this air, and 

 by the remainder flame was supported. Plumbago therefore 

 contains likewise aerial acid ; a great part of which is attracted 

 by the alkali of nitre. 



SECTION VII. 



One might perhaps suppose that this aerial acid arose 

 from the nitre itself. To this I answer, if such was really 

 the case, we should obtain aerial acid in all other detonations 

 with nitre. I therefore mixed (a) half a drachm of tin filings 

 with 2 drms. of nitre, and detonated the mixture in the 

 manner above mentioned. I thus obtained as much air as 

 occupied the space of 4 J oz. of water ; but this air contained 

 not the least mark of aerial acid ; it did not extinguish a 

 candle. (&) From 1 drm. of regulus of antimony, detonated 

 with 2 drms. of nitre, a quantity of air was obtained, which 



