possessing the Properties of Tannin. 65 



Even the decoction of coffee did not yield any precipitate 

 by this method, until several hours had elapsed, and I found 

 that the precipitate so formed was permanentiv soluble in 

 boiling water. But to explain this, we must recollect, it is 

 extremely probable, that some peculiar nicety is required in 

 the roasting of such bodies before the tanning substance can 

 be developed ; and this seems to be corroborated by some 

 experiments which I made on the decoction of a sort of 

 coffee prepared from the chicoree (1 suppose endive) root, 

 which was given me by Sir Joseph Banks ; for although this 

 decoction did not afford an immediate precipitate with 

 solution of gelatine, and although the precipitate was also 

 apparently dissolved by boiling water, yet upon cooling, the 

 same precipitate was reproduced in its original state. I am 

 therefore inclined to believe, that the tanning substance is 

 really developed in many of the vegetable bodies by heat, but 

 that a certain degree of temperature, not very easy to deter- 

 mine, is absolutely requisite for this purpose. 



Before I conclude this section, it may be proper to ob- 

 serve, that when a small quantity of nitric acid was added 

 to any of the above-mentioned decoctions, and when these 

 had been subsequently evaporated to dryness, and afterwards 

 dissolved in distilled water, they were converted into a 

 tanning substance perfectly similar to that which is produced 

 by the action of nitric acid on the varieties of coal. 



§VI. 

 In the preceding paper, a variety of the tanning substance 

 was slightly noticed, which was formed by the action of 

 sulphuric acid upon common resin, elemi, amber, &c. &c. 

 and as an instance has occurred of the formation of the 

 same substance from camphor, accompanied by circum- 

 stances which tend to increase our knowledge of the proper- 

 tics of the latter, I shall here describe this experiment. 



Experiment on Camphor with svlphitric Acid. 



The effects produced on camphor by sulphuric acid have 

 been bufvery superficially examinedj for all that has hitherto 

 been stated an)ounts to this, that camphor is dissolved by 



Vol. 24. No. 93. Fvb. 1806. E sulphuric 



