Sulsta7ice possessing the Properties of Tannin. 321 



until the whole of the acid had come over j after which it 

 was poured back upon the residuum, and the distillation 

 was thus repeated three times. 



Care w^as taken not to over-heat the residuum, and this, 

 when examined, did not appear to have suffered alteration 

 in any of its properties. 



2. Ten grains of the artificial tanning substance, mixed 

 with ten grains of white sugar, were dissolved in half an 

 ounce of nitric acid, and the whole was distilled to dry- 

 ness. 



The residuum, being then dissolved in boiling distilled 

 water, and examined by solution of gelatine and other re- 

 agents, was found to be unchanged in every respect. 



3. This resembled the former, only that gum arable 

 was employed in the place of sugar. The result was the 

 same. 



4. A quantity of dissolved isinglass was precipitated by 

 a solution of the artificial tanning substance, and the pre- 

 cipitate, having been well washed with hot distilled water, 

 was afterwards gradually dried. It was then digested in 

 strong nitric acid, which after some time acted powerfully 

 upon it> much nitrous oas was evolved, and a dark brown 

 solution was formed. This was evaporated to dryness, 

 and, after having been completely dissolved in boiling di- 

 stilled water, was examined by nitrate of lime, acetite of 

 lead, muriate of tin, and solution of isinglass, all of which 

 formed copious precipitates, similar in every respect to those 

 produced by the artificial tanning substance, which had nol 

 been subjected to the above described process. 



5. A portion of the precipitate, formed by isinglass and. 

 the tanning substance, was dissolved in pure muriatic acid, 

 and u as afterwards evaporated to dryness. Boiling distilled 

 water dissolved only a small part, and the solution, which 

 v/as of a dark beer colour, did not precipitate gelatine, al- 

 though it acted upon muriate of tin and sulphate of iron; 

 for with the former it produced an ash-coloured precipitate, 

 and with the latter a slight dfposit of a reddish brown co- 

 lour. 



6. As so small a part of the precipitated isinglass had 

 been thus rendered soluble in boiling watfT, tb.e residuum 

 was treated with nitric acid, as in Experiment 4 ; after 

 which, being evaporated to dryness, it was found to be 

 completely soluble in water, and precipitated gelatine as 

 copiously as at first. 



7. I dissolved twenty grains of the pure tanning sub- 

 stance in about half an ounce of muriatic acid ; but, after 



Vol. 23. No. fjc. Jan. Ib06. X disuliatiou 



