ofPigotite and the Resins. 383 



5. That when treated with nitric acid, the native mudesite, as 

 well as the mudesous acid itself, are oxidized and converted into a 

 new brownish-yellow, soluble and deliquescent acid, containing more 

 oxygen, and in the anhydrous state represented by C 12 H 5 O 10 . 



6. That this new acid, the mudesic, combines readily with alu- 

 mina and protoxide of mercury, giving salts of a yellow colour. 

 Both the acids described in this paper are distinguished for their 

 tendency to precipitate alumina and the protoxide of mercury. The 

 mudesate of mercury dried at 300° F., is represented by (2 H y O -f- 

 C 12 H 5 10 ). 



7. That chlorine, when made to act on either of the acids, or 

 their salts of alumina in contact with water, gradually deprives them 

 of all colour, while, at the same time, muriatic acid is formed. Col- 

 lected on the filter, boiled in water till the washings cease to pre- 

 cipitate nitrate of silver, and dried, the white gelatinous, apparently 

 altered mudesite or mudesate, is found on analysis to contain no 

 atomic proportion of chlorine, but to have sensibly the constitution 

 of the mudesic acid, or mudesates prepared by the direct action of 

 nitric acid. The author thinks it not unlikely that a chloro-mudesic 

 acid exists, and may be formed during this process, represented 

 probably by C ]2 H 4 C1 O ]0 , but which he has not succeeded in ob- 

 taining in a separate state. 



The mudesous and mudesic acids are distinguished from each 

 other by giving, the former brown, and the latter yellow precipitates 

 with the neutral metallic salts — by being, the former unaltered, and 

 the latter deliquescent in the air. Both form deliquescent salts with 

 ammonia, and appear to undergo alteration by the long- continued 

 action of hydrosulphuric, or of concentrated sulphuric and hydro- 

 fluoric acids. 



7. On the Constitution of the Resins, Part V. By James F. W. 

 Johnston, Esq., M.A., F.R.S.* 



In this paper the author continues his examination of what are 

 called the fetid resins, and from repeated analyses deduces for the 

 resin of Sagapenum the formula C 40 H 2y O, , and for that of Galbanum 

 C 40 H 27 7 . He then compares the formulae for the four resins : 

 Opoponax = C 40 H 25 14 , Assafcetida = C 40 H 26 O l0 , 

 Galbanum = C 40 H 27 70 , Sagapenum = C 40 H 2 ,,0 9 ; 

 and considers it probable 'that, though no striking analogy among 

 the ^rational formulae for these resins is perceptible, by which their 

 analogy in physical properties can be accounted for, they may pos- 

 sess an analogous rational constitution which future researches may 

 disclose. 



Euphorbium consists of two resins, of which the more soluble, 

 A, gave the formula C 40 H 31 6 . Elemi also consists of two resins, 

 of which the more soluble, A, is represented by C 40 H 32 4 , and the 

 less soluble, B, by C 40 H 32 0„ as had previously been shown by Hess 



* Abstracts of the preceding series will be found in Lond. and Edinb. 

 Phil. Mag., vol. xv. p. 327, and present vol. p. 147. — Edit. 



