REMARKS 0N DR. THOMSON'S CHEMISTRY. 247 



Speaking of maftich, vol. 3, p. 311. Dr. Thomfon Dr. Thomfon'a 



fays, it is readily foluble in alcohol. In the lame valuable ^ c °"" t ° 



volume, page 332, he informs us, that " that part of maftich 



which is infoluble in alcohol is faid to be pure caoutchouc." 



In invefligating this apparent contradiction, I examined the The Author's 



action of alcohol upon maftich, and found that nearly a fifth ex P erime » ts - 



part of it remained undifiblved. This refiduum, after re- Alcohol leaves 



peated wafliings in alcohol, was white, conliderably elaftic, one „^ th of ,., 

 i .. r ■ • « 1 1 i i . i maftich undif- 



and adheuve; it was inflammable; and when heated became folved, 



brown, emitting inflammable gas. In this ftate it had much refembling 



the appearance of common Indian rubber, but fomewhat Indlan rubber# 



glutinous : It was not in the lead: acted on by water. 



I was induced to try the effects of different menftrua on Comparative ex- 



this refiduum, and on the elaftic gum caoutchouc, with a P e r' ments on "^ 



r .,..,. , - r „, r „ . refidueofmas- 



view to aiceriain their identity or otherwile. Ine tollowing t i c h, and on 



are the refults I obtained : caoutchouc. 



Sulphuric ether, previoufly waftied with diftilled water, 

 diflblved this refiduum as well as caoutchouc. 



Alcohol precipitated both thefe fubftances from their folvent 

 in the form of a white curd. 



Water had no action on the folutions. 



By the nitric acid the refiduum was converted into a yellow 

 brittle porous mafs, nitrous gas being di (engaged from the 

 acid. 



Nitric acid did not a6l fo eafily on caoutchouc; but when 

 raifed to the boiling point it changed it into a fimilar fub- 

 ftance. 



With the fulphuric acid a fubftance like charcoal was form- 

 ed, the acid affuming a dark port wine colour, part of it being 

 converted into fulphureous acid. 



The fame effect was produced by the fulphuric acid on 

 caoutchouc, though not without the afliftante of heat. 



Neither the muriatic qr oxymuriatic acids appeared to have 

 any action on either of thefe fubftances. 



Acetic acid diflblved a fmall portion' of the refiduum, but 

 had no action on caoutchouc. 



Solutions of potafh and ammonia produced no effect on 

 either the refiduum or caoutchouc. 



From the above experiments it will be obferved, that the Thefe appear to 

 acids act with greater facility on the infoluble part of maftich, be the Um -> 

 than on caoutchouc. Notwithflanding this difference in their 



aclion. 



