219 



taining the largest amount of oxygen of any resin hitherto ana- 

 lysed. The resin of jalap, obtained by evaporating the alcoholic 

 extract, and afterwards boiling it in water, is represented by 

 C40 H34 Ojg, and in the amount of oxygen it contains is only 

 surpassed by the resin of scammony. It is interesting to remark 

 that these two resins in their effects on the animal economy are as 

 nearly related as these formulae show them to be in chemical consti- 

 tution. 



The resin of labdanum, extracted by alcohol from the crude 

 labdanum and evaporated, gave the formula 04,, H33 Og ; but this 

 extract, softened in the air and water, took up from it a bitter sub- 

 stance of a brown colour. After boiling in water, the pure resin 

 is represented by C40 H33 O^. 



The Berengela resin, previously analysed by the author before he 

 was aware of the conditions necessary to be attended to in order to 

 obtain a resin in its normal state, is expressed by the formula 

 C40 H30 O7 ; and the resin of Retin asphalt, also previously analysed 

 by the author, by C40 Ho^ Og. 



The resin of ammonia, extracted by alcohol from the crude gum 

 resin, is represented by C40 H^^ Og ; the resin of opoponax by 

 C40 O14; and that of assafoetida by C40 Hog O^q. 



A striking relation appears between the formulse for the resins of 

 ammonia and assafoetida, the former being C40 H05 Oy, the latter 

 C40 Hgg Oio, as if the latter were merely a hydrate of the former. 

 The author considers this relation, and concludes that it is only ap- 

 parent, and that probably in neither of the resins does any of the 

 hydrogen exist in combination with oxygen in the state of water. 



This leads the author to inquire into the general action of a 

 slightly elevated temperature on the resins, and he concludes that in 

 all cases when a resin in its normal state is heated a few degrees 

 above its melting point, it begins to suffer partial decomposition, 

 accompanied by the solution of water, and always by more or less 

 of a volatile, generally oily compound, sometimes containing less 

 and sometimes more oxygen than the resin which has been sub- 

 jected to heat. In the case of some resins, especially such as 

 are agreeably fragrant, and are expressed by the second of the 

 author's general formulae C40 H24 + a: O^, benzoic acid is one 

 bf the products of decomposition at a moderate temperature. 

 Thus the resin of dragon's blood gives only a trace of benzoic 

 acid, with water and a red volatile compound ; while the resin 

 of benzoin gives much benzoic acid. Some resins give off vola- 

 tile matters and diminish in weight long before they reach the 

 fusing point ; as is the case with the resin of benzoin, of which 

 the melting point is high. With regard to the special action of 

 such temperatures in altering the atomic constitution of the resins, 

 the author finds that each resin undergoes a change, probably pecu- 

 liar to itself, and probably depending on the nature of the organic 

 radical it contains. Thus, the formula for the resin of retin asphalt 

 (= Cjo H07 Og) by prolonged heating at the melting point becomes 

 ^40 H37 O5. Ammonia resin (= C40 H03 Op) by heating at 270*^ 



