Q56 6tJJ * -ARABIC AND GTJM ADRACANTH^ 



VI. 



Experiments on Gkm Arabic and Gum Adraca'nth. 

 By M, Vauquelin *. 



Red gum adra- JL EN" grams of red gum adracanth produced on combuftion 

 combuftion^f tl,ree digrams and a half of white allies. Thefe allies 

 hundredths diflblved in muriatic acid with effervefcence, and gave forth 

 ofnmir^t°ha ean odour of Sulphurated hidrogen. Their folution depofited 

 little iron and a precipitate by ammonia, which was phofphate of lime and 



nme? 11316 Qt ° Xide ot ir0n * The oxalate of ammonia precipitated from it 



much lime. Thus red gum adracanth contains in 100 parts 



about 3f of aflies, which was compofed for the moft part of 



carbonate of Jime, a fmall quantity of iron, of phofphate of 



lime, and perhaps of a very minute portion of alkali. 



"White gum 2. Ten grains of white gum adracanth fubmitted to the 



adracanth left a fame proofs, gave three decigrams of alhes, which wese com- 



which contain- P°fed of the fame principles as the red kind, with the ad- 



cd the fame dilion of a little potafh. 



prmc^ples and fr Ten gft | n | of gQm ^^^ hmnt ^ ^ ^^ ] eft thrce 



Gum arable left decigrams of afnes, which were compofed of the fame 



3 containing no e | ements as t ^ e preceding, except that they gave no fign of 



the prefence of alkali or of fulphur. 



Opacity and I formerly thought that the opacity of gum adracanth, and 



difficult folu- th e difficulty of its folution in water, might be occafioned by 

 bility of gum ,". „ , , r , r 



adracanth. a greater proportion of earthy matter; but after thele ex- 



periments it appears, that they are due to another caufe. 

 The lime in T<he Jime which I found in the gum, which I am about to 



gums is com- mention, was doubrfefs- neither in the llate of carbonate, and 

 forminaa ' ' ' ^' ^ e * s ' n tliat °^ quicklime ; for the folutions of the gum 

 ibluble fait. were not in the leair alkaline, but on the contrary, flightly 

 acid ; at leaft a bit of the gum rubbed on fome paper well 

 ' jnoificned (with blue vegetable juice) made it fentibly red. 

 It is alfo certain, that oxalate of ammonia and carbonate of 

 polalh oceaiion precipitates in the folution of gum arabic, and 

 that acetite of lead does not form any. It follows from this, 

 that the lime is moft probably united to fome acid in the 

 gums, which doubtlefs is a vegetable acid ; for in being 

 decomposed they leave their bales combined with carbonic 



* Annales de Chimie, Tom. 54. 



acid; 



