215 
Mr. Hatchett on an artificial tanning Substance. 
Having thus by means of nitric acid obtained solutions from 
asphaltum, from jet, from several of the pit-coals, and from 
charcoal, I evaporated them to dryness in separate vessels, 
taking care in the latter part of the process to evaporate very 
gradually, so as completely to expel the remainder of the 
acid without burning the residuum ; this, in every case, proved 
to be a brown glossy substance, which exhibited a resinous 
fracture. 
The chemical properties of these residua were as follows. 
1. They were speedily dissolved by cold water and by 
alcohol. 
2. Their flavour was highly astringent. 
3. Exposed to heat, they smoked but little, swelled much, 
and afforded a bulky coal. 
4. Their solutions in water reddened litmus-paper. 
5. The same solutions copiously precipitated the metallic 
salts, especially muriate of tin, acetite of lead, and oxysulphate 
of iron. The colour of these precipitates was commonly brown, 
inclining to that of chocolate, excepting the tin, which was 
blackish-gray. 
6. They precipitated gold from its solution, in the metallic 
state. 
7. They also precipitated the earthy salts, such as the 
nitrates of lime, barytes, &c. &c. 
8. The fixed alkalis, as well as ammonia, when first added 
dissolved, have been noticed by Professor Lichtenstein in Cr ell’s Chemical 
Annals, 1786; by Mr. Lowitz ; (Crell’s Chem. Journal, translated into English, 
Vol. II. p. 255;) and by Mr. Jameson, in his Outline of the Mineralogy of the] 
Shetland Islands, &c. 8vo. edit. p. 167. 
