ARTIFICIAL TAN* '31 



fo as to make them yield tan ; which opinion was corroborated 

 by experiments made by decoftion of chicoree (probably en- 

 dive) root, prepared in the fame manner, which produced a 

 precipitate with gelaten after feme time, though not at firfl, 

 which was apparently diflblved in boiling water, but depofited' 

 again in its original ftate, on cooling. The author therefore 

 is inclined to believe that the tanning fubftance is really de- 

 veloped in many vegetable matters by heat alone; but that a 

 certain degree of heat, not eafy to determine is abfolutely ne- 

 cellliry for this efFeft. 



A ("mail quantity of nitric acid added to any of the decoc- Nitric acid added 

 tions juft mentioned, and evanorated to drynefs, produced a ^? ^'^^'^ ^^'^"*=- 



■' * . tions gives tan- 



refiduum, having all the properties of the tan produced from ning properties 

 QQ2i\^ to their refidu^. 



§ VI. 

 The produ6tion of a variety of the tanning fubftance before 

 mentioned, by the a6tion of fulphuric acid on the refms, am- 

 ber, &c. fuggefted the following experiments on camphor; 

 the refults of which tend to increafe the knowledge of its pro- 

 perties. 



Experiments on Camphor zdih Sulphuric Acid. 



The only fafts hitherto related relative to the efFefts of i\xU 

 phuric acid on camphor, arc that a brown or reddifli brown 

 foiution is formed, from which water precipitates the camphor 

 unchanged ; but this only happens at a certain period of the 

 operation ; for if it be longer continued, the following efFeds 

 will be produced. 



A. One ounce of concentrated fulphuric acid was added Experiments 

 to one hundred grains of camphor, which diflblved gradually, ^^^\ "^ "'?^ 

 after firft becoming yellow ; in about an hour, the liquor having 

 progreflively changed to reddifti brown, brown, and at lad 

 biackifh brown, much fulphureous acid gas was produced, 

 and continued to encreafe during four hours, when the whole 

 appeared a thick black liquid, having no other odour but that 

 of fulphureous acid ; alter two days the produ(^ion of the gas 

 was much diminifhed ; the containing alembic was then put in 

 a fand bath, moderately hot, by which more fulphureous gas 

 was obtained ; but (his foon abated ; at the end of two da)s 

 more, fix ounces cf water was gradually added, by which the 



liquor 



