SiS ARTIFICIAL TAN. 



(an, to promote Its deftrudibility ; and exprefTes his belief 

 that mucilage or gum renders the fubftances that contain It 

 » more deftruftible in the nitric acid, and in fome cafes alfo 



prevents or impedes the formation of the tanning fubftance; 

 which difference he thinks to be caufed by the mucilage 

 being in a Hate of chemical combination in thofe bodies. 



§ III. 



Experiments on A and B. When fulphuric or muriatic acid was added to 

 thcaitificialtan. ^ folution of the new tan, it became turbid and depofited a 

 brown precipitate, which was foluble in boiling water, and 

 was then capable of precipitating gelatine; in which particu* 

 lars it refembles ihe tannin of galls and other vegetable fub- 

 ftances. 



C. Carbonate of potafli, added to a folution of the new 

 tan, deepened the colour ; the liquor became turbid, and de» 

 pofited a brown magma. 



D. Five grains of dried artificial tan were dilTolved in half 

 an ounce of ftrong ammonia : the whole was then evaporated 

 to drynefs ; and being diflblved in water was found not to 

 precipitate gelaten, unlefs a fmall portion of muriatic acid was 

 previoufly added. 



E. Another portion diflolved in ammonia was diflilled : At 

 firft ammonia came over, and afterwards a yellow liquor, that 

 had the odour of burned horn. The refiduum was infoluble 

 hi water, to which it only gave a flight yellow tinge. 



On diftillation it F. The objeft of this experiment is to (hew the ftrange pro- 

 has an odour of -, ^^- ^j^^ ^^^ ^^^ ^f giving produfts analogous to animal 



turccd horn, '^ ■' . . . 



and yields aai- matter (of which it yielded the odour in combuftion on former 

 mouia. trials), though prepared itfelf from vegetable fubflances. 



Some prepared from dry vegetable charcoal was diftilled : 

 Firfi: a liule water came over, then a little nitric acid, then 

 a very fmall portion of a yellowifii liquor: The fire being 

 then raifed, the velfels fuddenly became filled with a white 

 cloud, and fo great a torrent of gas was almoft explofively 

 produced as to overfet the jar : This gas, by its fmell, ap- 

 peared fo be ammonia, and was formed into the cloud by the 

 nitric acid vapour in the vefiels. The next jar of gas, which 

 came flowly over, was carbonic acid, except a very fmall 

 part which feemed nitrogen gas. A bulky coal remained, 

 ihat on incineration gave if grains alhes, which confided 

 \ rincipally of lime. 



G. Fifty 



