S6 . TANNING MATTER, 8zC, 



1. 



Experiments, Two hundred grains of oak bark, reduced into vcrv 

 iidarsubstancc ^^^^^ fragments, were infused in about four ounces of 

 having the cha- water, after which the infusion was examined by dis- 

 racters 6f tan- solved isinglass, and yielded a considerable precipitate. 



2. 



Two hundred grains of the sp^rae sort of bark were 

 slightly roasted, and afterwards digested in water ; a much 

 darker coloured liquor was obtained than in the former 

 case ; but although it afforded precipitates by the addi- 

 " tion of the muriate of tin, acetite of lead, and sulphate 



of iron, yet not tine smallest effect was produced by so- 

 lution of isinglass. 



3. 

 The residuum, with the remaining part of the above 

 mentioned liquor, was then digested w^ith a small portion 

 of nitric acid; this was co'.npletely evaporated, and a 

 brown solution was formed by water, w hich abundantly 

 precipitated gelatine. 



4. 

 One ounce of oak bark, reduced into very small frag- 

 ments, was repeatedly digested in different portions of 

 water until the whole of its tannin w as extracted. The 

 residuum or exhausted bark (as it is called by the tanners) 

 was dried, and was afterwards moderately roasted. It 

 was then moistened with diluted nitric acid, which was 

 evaporated in a heat not much exceeding 300° until the 

 bark was become perfectly dry. This was digested in 

 water, and speedily formed a yellow^ish-brown liquor, 

 which abundantly precipitated gelatine. 



5. 

 The bark, which after being exhausted of its natural 

 tannin, had thus afforded the artificial tanning substance, 

 was repeatedly treated with water until the whole of this 

 last was extracted. The bark was then again slightly 

 roasted, was again moistened with nitric acid, and was 

 gently heated and dried as before. Water beirg poured 

 on it and digested, formed a brown solution, which copi- 

 ously precipitated gelatine. 



1 'The 



