99 



-with many oxydising substances (nitrous acid, chlorine, &c.). It 

 •consists of about 70°/^ guaiaconic acid, 10°/^ acid guaiacum-iesin, 

 10°/q beta-resin, and of guaiacic acid, and guaiacum-yellow. 



Guaiaretic Aciclo C40 H26 Os + HO. In guaiacum-resin, 

 •constituting 10°/^ of it. Boil the jiulverised resin with half 

 its weight of caustic lime and sufficient water for half an hour, 

 strain, dry the residue and exha^^st with hot alcohol, distil ofi' 

 the alcohol from the tincture, dissolve the remnant in soda-ley, 

 allow the solution to stand cold, pi-ess the soda salt, recrystallise 

 in water with a little caustic soda, decompose with hydrochloric 

 acid, and crystallise in alcohol. — Soft, small warty and scaly 

 crystals, of a faint odour of vanilla, when crystallised in acetic 

 acid inodorous bi-ittle needles, when crystallised in diluted alcohol 

 shining laminse ; fuses at 75° to 80° under loss of water, by rapidly 

 heating mostly volatilised without decomposition ; insoluble in 

 water, dissolves in 1"8 parts alcohol of 90°/^, likewise in ether, 

 also in chloroform, sulphide of carbon, acetic acid, benzol ; in con- 

 centrated sul^^huric acid with purple colour, and repi-ecipitable by 

 water with white colour ; little soluble in liquor of ammonia. Its 

 compounds with the fixed alkalies dissolve I'eadily in water. 



Guili:=:Ci2 Hii Oil. Just as scarcely any part of a i)lant is 

 without fibre, so in all likelihood no plant is without gum ; at all 

 events, gum is obtained in every phyto-chemical analysis, though the 

 quantity obtained is sometimes exceedingly small. Being in- 

 soluble in ether, and as alcohol dissolves scarcely traces of it, the 

 ^um always occurs in aqueous extracts, being exti-acted completely 

 on account of its ready solubility in the solvent. The qualitative and 

 quantitative determination is efiected by boiling the extract (pre- 

 pared with cold water) for a short time, filtering ofi" a flocky tur- 

 bidity (albumen), concentrating to a small bulk at a gentle heat, and 

 mixing the residue with alcohol of 95% in small quantities as long 

 as any cloudiness is produced. The viscid, dough-like precipitate is 

 washed with alcohol, re-dissolved iii as little water as possible, the 

 solution precipitated as before with alcohol, the deposit washed 

 with alcohol, dried at 100°, and weighed. 



The gum, as obtained by this process, contains generally more or 

 less foreign matters, as inulin, sugar, dyeing substances, minei'al 

 salts, (fee, to remove which completely is most difficult or im- 

 possible. Should the gum, thus repeatedly precipitated with 

 alcohol and then diied perfectly, be soluble in an equal weight of 

 cold water, then it contains either no inulin or only so little 

 (one-fifth per cent, or less) that this can be left out of considera- 

 tion. But, as inulin is convertible into gum with comparative 

 ease, it is also possible that a portion of the gum obtained may 

 have been originally inulin. 



Another contamination of the gum, obtained as above, consists 

 of pigments of various kinds. They are almost never absent, and 



H 2 



