ARTIFICIAL TAN. , 3QJJ 



eflfential properties they proved fimilar to thofe formed 'by the 

 varieties of tannin hitherto known, except that they contained 

 no galtic acid or mucilage. 



Animal coal from iiinglafs was alfo tried in the fame manner, Refiduumof 

 this diflblved very (lowly, but left a little of the coal ^^^^^ 

 changed, its folution was of a deeper colour, and managed as qualities, nearly, 

 the others defcribed, produced fimilar effects with the re- 

 agents, except fome difference in the colour of the precipi- 

 tates; and alfo gave an infoluble precipitate from the folu- 

 tion of iiinglafs; by which the curious fact is proved, that 

 one portion of the (kin of an animal may be made to convert 

 another into leather. 



Coak gave a fohition refembling that of pit coal, but did a "d of coak alfo. 



not produce the fame yellow precipitate. 



Thefe experiments (hew, that the tanning fubftance is beft Tanning fufa- 

 . r , , . • ; , • , ftance beft pro- 



procured from carbonaceous matter when it is uncombmed « ure d from car- 



with any fubftance but oxigen ; which was confirmed by h ™> uncombined 



experiments on Bovey coal, SuiTex coal, Surturband from butoxken."* 



Iceland, and deal faw-duft, which being dilToKed in nitric 



acid, and evaporated, the refidues diffolved in water, neither 



precipitated gelalen, or (hewed any other figns of tanning 



matter; but when the fame materials are charred, and 



treated as before defcribed, they copioufly produced the 



artificial tan ; as did alfo teak wood, which Mr. Hatchett had 



proved to contain neither tannin or gallic acid in its un- 



chaired itate. 



Mr. Hatchett had made feveral experiments on the flow Carbonization of 

 carbonization of vegetable matters in the humid way, princi- b^fufphuric* ^ 

 pally by fulphuric acid, occafionally diluted.- Concentrated acid, 

 fulphuric acid poured on any refinous fubftance reduced to 

 powder, diffolves it in a few minutes ; the folution is trans- 

 parent, of a )dlow brown colour, and a vifcid oil-like con- 

 fidence, but after being placed on the fancl bath, grows darker, 

 evolves fulphuric acid gas, and at laft becomes a thick liquid 

 of an intenfe black. 



Sulphuric acid of the above ftrength poured on common Effects of folu- 

 turpentine dilTolves it readily, if a portion of the folution is t |°" j° n fu]p P b" r '; c 

 then dropped into cold water, a precipitate of common yellow acid dropped iu to 

 refin is formed ; if after another hour or two, another portion wate S* 

 is treated in the fame way, the re tin produced is of a dark 

 brown, and that thus formed from a folution that has flood 



£v« 



