153 P^ COPAL VARKISHES. 



feparate again *. When the camphor Is diflblved in the fpirit, 

 the finall bits of copal thrown into it and inftantly made to boil, 

 the motion of ebullition keeps the camphor fufpended, moves 

 the copal about in the fpirits, the furface of each bit of copal 

 is diflblved, and the whole of it foftened and enlarged, and by 

 —and why Mr. continual boiling may be diflblved ; but ray friend did not pro- 

 S.'s friend failed, ceed in this way ; he reduced his copal to a very fine powder, 

 thinking, perhaps, that would facilitate the folution ; he then 

 added the camphor, diflblved in the fpirit of turpentine, but 

 fearful of giving too much heat, fet it by the fide of his fire 

 till it was warmed, then moved it into a warmer place, and 

 at lad made it boil ; the confequence was that the camphor + left 

 the fpirit and united with the copal to form one folid coherent 

 mafs at the bottom of the veflel ; the thicknefs of this mafs 

 prevented the heat from penetrating to the fpirit fo foon as i' 

 otherwife would have done ; and, when at laft it did boil, the 

 camphor had entirely left it, and of courfe it was impoffible 

 that any folution (hould take place. 



Three times was the folution attempted in this manner, but 

 when on a fourth trial by myfelf a fufficient quantity of cam- 

 phor was added and the boiling heat immediately applied, the 

 folution went on, but not fo favourably as in my other attempt, 

 becaufe the copal was united into one mafs at the bottom of 

 the veflel, and no more could be expofed to the a6lion of the 

 folvent than the furface ; but, in the other experiment the 

 copal was broke into very fmall bits and the furface of each 

 expofed to the full adion of the folvent ; of courfe a greater 

 quantity was diflx)lved in the fame fpace of time. 

 Thelnftanccof Had this gentleman been fatisfied with the experiment he 

 failure here ^^jg^ jjy hm^fgif he might have reported, from his own expe- 

 mentioned might . •^, ,7 , ,.S , r 



have been urged rience, that copal could not be diflblved by the procefs I had 



againft the defcribed ; and yet in point of fa£l, nothing could have been 



more untrue : from this it may be fairly deduced that when 

 perfons who are unufed to fuch experiments do undertake them 

 they (hould be fcrupuloufly exa6l in following the directions 



* Six montlis ago I reduced fome copal to this ftatej it has re- 

 mained ever fince expofed to the open air in a hot room, and ftill re-n 

 mains foft, the particles adhering to each other. 



f When the fpirit of turpentine was poured off from the copal 

 it was perfeftly colourlefV, and by the fmcU did not in the leaft ii 

 dicate the prefence of camphor. 



giv< 



