322 Experiments and Remarks on a Substance 



distillation to drvness, the residuum in every respect ap- 

 peared to be unchanged. 



In addition to the above experiments may be added, that 

 the solutions of the artificial tanning substance seem to be 

 completelv imputrescihle, neither do they ever become 

 nioiildv, like the infusions of galls, sumach, catechu, &cc. 



Having thus ascertained the very unchangeable nature of 

 this substance, i made the following comparative experi- 

 nients on galls, smnach, Pegu cutch, kascutti, coaunon 

 cutch, and oak bark. 



8. Twenty grains of powdered galls were dissolved in 

 half an ounce of the strong nitric acid; the solution was 

 then evaporated to dryness, and the residtmnT dissolved iu 

 boiling water. This did not produce the smallest effect on 

 dissolved gelatirie. 



9. A strong infusion of galls, evaporated to dryness, and 

 treated as above, was totally deprived of the tanning property. 



10. Isinglass precipitated by the infusion of galls was 

 dissolved in nitnc acid, and examined as in Expernnent 4 j 

 but no trace of tannin could be discovered. 



11. Twenty grains of sumach wtTC dissolved in half an 

 ounce of the strong nitric acid, and treated as in Experi- 

 ment 8 ; after which it appeared that the tannin was de- 

 stroyed. 



12. Twenty grains o-f Pegu cutch (which contains a con- 

 siderable quantity of mucilaoe) were subjected to a similar 

 process, by which much oxalic acid was obtained, but every 

 restige of tarmin was obhterated. 



13. Twenty grains of the catechu called kascutti afforded 

 results similar to the above. 



14. Twenty grains of the common cutch or catechu, 

 being dissolved in nitric acid, evaporated to dryness, dis- 

 solved \n water, and examined by solution of isinglass, 

 rendered the latter turbid : a tenacious film was deposited, 

 which was insoluble in boiling water, and was evidently 

 composed of gulatine and tannin. 



13. Twenty grains of prepared oak bark, by the like 

 treatment, afforded a solution in water, which still acted 

 in some measure upon gelatine, as it caused a solution of 

 isinglass to become slightly turbid ; and a film, completely 

 insoluble in boiling water, was, as in Experiment 14, de- 

 posited on the sides and bottom of the vessel. 



16. Infusions were prepared, as nearly as possible of 

 equal strength, from galls, sumach, shavings of oak wood, 

 oak bark, and the artificial tanninij substance: half an 

 ounce, in measure, of each was then put into separate 



glasses. 



