24(? REMARKS ON DR. THOMSON'S CHEMISTRY, 



andbyHoffmann. Hoffmann alfo, by the method he employed in diflblving 

 amber with cauftic nitre, evinced that, he was acquainted with 

 this property in alcalies. Dr. Thomfon defcribes Mr. Hatchett 

 as the firft difcoverer of the aclion of alcalies upon refin. The 

 fa£b above quoted will lefTen the originality, without diminifii- 

 ing the value of Mr. Hatchett's ingenious experiments. 



How therefore it can be true that, «' all chemifts both 

 ancient and modern, have affirmed, that the alcalies do not 

 exert any action on the reiins" ] cannot eafily difcern, um? 

 lefs indeed we impute to them the mod palpable contradic- 

 tions, an error which I believe is not often found in their 

 writings. 



Dr. Thomfon Page 340 in the fame volume, Dr. Thomfon afferts, that 



aflferts, that one fandarach is not foluble in alcohol, about a fifth part of it re- 

 fifth of fandarach . . • . ' 

 is infoluble in maimng unditlolved; and deicnbes the infolubie part as pol- 



akohoi. feffing peculiar properties, differing from fandarach, and calls 



it fandaracha. It ought not to be concluded, that Dr. Thomfon 



himfelf can have chemically examined every fubflanre he muft 



have occafion to defcribe in a work which embraces lb great 



a variety ; but the importance of fandarach as an ingredient 



in varnifhes being nearly equal to that of any other refin, this 



fubftance certainly deferves more attention from chemifts 



than has hitherto been beftowed on it. The properties of this 



refin as mentioned by Dr. Thomfon, are ftated to reft folely 



on the authority of Giefe, no other chemift having examined 



it. 



Experiment. It Upon trial I found that fandarach was foluble in eight times 



proved foluble in fa weight of alcohol, a very minute proportion only being left, 



weight of ' which appeared to confift almoft entirely of extraneous matter. 



alcohol. Confequently the fubftance Dr. Thomfon has denominated 



fandaracha can have no exiftence in this refin. It is proper 



to obferve, that the refin I made ufe of was lelecled fine, and 



is known in commerce by the names of gum juniper and 



fandarach. From the obvious disagreement in the refu/ts, 



perhaps we ought to conclude, that the fubftance employed 



by Giele in his experiments was not true gum fandarach *. 



* Looking to fome chemical notes, I find that when three or four 

 tears of fandarach were put into pure alcohol, and left for a day, 

 a fmall quantity of thick fluid remained at the bottom, which, 

 however, was taken up by agitation, and the whole became femi- 

 opake: — It is remarkable, that this fubftance is not foluble in tallow 

 or oil, as common refin is. N. 



4 Speaking 



