ANALYSIS ,OF GUM AMMONIACUM. 347 



4. Sulphuric acid dissolves the rcssin of olibanum without 

 heat, forming a red solution, from which water throws 

 down a white precipitate. If it be heated some time, water 

 separates from it a black resin, soluble in nitric acid ; 

 which by evaporation converts it into a brown residminj of 

 an astringent taste mixed with bitterness, and the aqueous 

 solution of which precipitates gelatine, but not sulphate of 

 iron. 



5. If the resin be treated to dryness with eight parts of Converted by 

 of nitric acid at 38^, it is almost wholly converted into the"V"^,^''!.'* ^"'* 

 resiniform matter, the properties of which 1 have already sinoamer. 

 piade known. The waters of elutriation, which contained 



no oxalic acid, yielded by evaporation a residuum, which, 

 when heated afresh with nitric acid, afforded none of the 

 tanning matter discovered by Mr. Hatchett ; but a bitter, 

 soluble substance, partly precipitated on cooling from its 

 solution in boiling water, soluble also in alcohol, and pro- / 

 ducing precipitates in several metallic solutions. 



This substance appeared to me to possess properties ana- 

 logous to those of what I have term<ed resinoanier, but it 

 differs from it in the stability and proportion of its elements. 



Art. VI. Analysis of Gum Ammoniacum. 



§ I. Gum ammoniacum, exposed to a heat not sufficient Action of heat 

 to decompose it, softens easily, and loses 6 per cent of its 

 weight. 



Twenty-five gram. [386 grs.] distilled with a naked fire 

 yielded 12 gram. [185*3 grs.] of liquid, the greater part of 



Fifty gram. [772 grs.] of resin, heated to saturation with solu- 

 tion of potash, dissolved entirely ; and by evaporation were ob- 

 tained 69 gram. [1065 grs.] of solid resinous soap, dry at alow 

 temperature, of a brown colour, and wkich I found to be per- 

 fectly similar to Starkey's soap. Baume and Legendre therefore Surkey's soap, 

 had reason to presume, that only the thick and resinous part of 

 oil of turpentine could really combine with potash; for this 

 alkali acts on volatile oil only by promoting its conversion into 

 resin to unite with it afterward. 



Volatile alkali, diluted with a great deal of water, also combines 

 with resin very readily, and quickly reduces it to the saponaceous ' 

 state. This compound diluted with water act^uues after a time the 

 thicii^e;£S of starch. 



•which 



on ammonia- 

 cum. 



