ART OF TANNING* 71 



1 . I iniufed tan, in the (late of fine powder, for fome hours lnfufion of tan 

 in water; I filtrated this folution, and treated it with Hme^^P^;- 

 water ; I obtained a preeipitaie in confiderablc abundance, wa ter. 

 which I collected upon a filtre, dried, and afterwards treated 



with alcohol, in order to afcertain whether it were foluble in 

 this menftruum ; but the alcohol was not even coloured by it. 



2. Wifhing to afcertain whether the lime had a greater affi- Acids difengage 



nity for the acids than for the tannin with which it was com- a p !! lve r Ulen \v„ 



matter horn the 



bincd, I treated four drachms of the precipitate of which I lime; 

 have fpoken above, with nitric acid diluted with water, with 

 the acid of a very gentle heat ; a pretty briik effervefcence 

 took place with a difengagement of carbonic acid gas; after 

 four hours infufion, I filtrated the liquor, which had affumed 

 a very deep tinge, and there remained upon the filtre a black 

 pulverulent fubftance, brilliant, having an acerb and very 

 flightly bitter tafle ; this refiduum weighed a little lefs than 

 two grammes. 



3. In order to afcertain whether the nitric acid had dif- by combining 

 folved any lime, I treated the liquid which I had filtrated with the lime ' 

 with the acidulous oxalate of potath, and I obtained an abun- 

 dant precipitate ; on which account I conjectured, that fince 



the nitric acid had diffolved the lime, the Jubilance which I 

 had obtained upon the filtre muft be tanin, as the precipitate 

 obtained by the mixture of the lime-water and of the infufion 

 of tan, was produced by the union of the tanning principle 

 and of the lime. In order to afcertain this point, I treated 

 one portion of it with water, and the other with alcohol ; I let 

 thefe fubftances infufe in the land bath for twenty-four hours : 

 the water became ltrongly coloured, and the alcohol more fo; and thepulveru. 

 but all the tannin (hitherto I only prefume that it is fuch) was 

 not diffolved ; the alcohol diffolved only a little more than 

 half of it, and the water lefs. I treated thefe two liquids, 

 after having filtrated them, with a folution of glue, and I ob- 

 tained a precipitate fimilar to that which is obtained by mixing 

 infufion of tan with the fame folution, but of a much darker 

 colour, and a little lefs elaflic. When I treated them with 

 the muriate of tin, I obtained a precipitate which became 

 gelatinous; when I treated them with lime-water, the tanin 

 combined with the lime, and reproduced the tanate of lime 

 already formed. 



According 



lent matter is, 

 tanin, 



