104 ZYGOPHYLLE^. 



Description — The resin occurs in globular tears ^ an inch to 1 inch 

 in diameter, but much more commonly in the form of large compact 

 masses, containing fragments of wood and bark. The resin is brittle, 

 breaking with a clean, glassy fracture ; in thin pieces it is transparent 

 and appears of a greenish brown hue. The powder when fresh is 

 grey, but becomes green by exposure to light and air. It has a slight 

 balsamic odour and but little taste, yet leaves an irritating sensation 

 in the throat. 



The resin has a sp. gr. of about 12. It fuses at 85° C, emitting a 

 peculiar odour somewhat like that of benzoin. It is easily soluble in 

 acetone, ether, alcohol, amylic alcohol, chloroform, creasote, caustic alka- 

 line solutions, and oil of cloves ; but is not dissolved or only partially 

 by other volatile oils, benzol or bisulphide of carbon. By oxidizing 

 agents it acquires a fine blue colour, well shown when a fresh alcoholic 

 solution is allowed to dry up in a very thin layer and this is then 

 sprinkled with a dilute alcoholic solution of ferric chloride. Reducing 

 agents of all kinds, and heat produce decoloration. An alcoholic solu- 

 tion may be thus blued and decolorized several times in succession, but 

 it loses at length its susceptibility. This remarkable property of 

 guaiacum was utilized by Schonbein in his well-known researches on 

 ozone. 



Chemical Composition — The composition of guaiacum resin was 

 ascertained by Hadelich (1862) to be as follows : — 



Guaiaconic Acid, , . . . . . . . 70'3 per cent. 



Guaiaretic Acid, . . . . . . . . lO'o ,, 



Guaiac Beta-resin, . . . . . . . 9"8 ,, 



Gum, 37 ,, 



Ash constituents, . . . . . . . .08 ,, 



Guaiacic Acid, colouring matter (Guaiac yellow), and | ^.^ 



impurities, ....... i " 



If the mother liquor obtained in the preparation of the potassium 

 salt of guaiaretic acid (vide infra) is decomposed by hydrochloric acid, 

 and the precipitate washed with water, ether will extract from the mass 

 Guaiaconic Acid, a compound discovered by Hadelich, having the 

 formula C^H^O^". It is a light brown, amorphous substance, fusing at 

 100° C. It is without acid reaction but decomposes alkaline carbonates, 

 forming uncrystallizable salts easily soluble in water or alcohol. It is 

 insoluble in water, benzol, or bisulphide of carbon, but dissolves in 

 ether, chloroform, acetic acid or alcohol. With oxidizing agents it 

 acquires a transient blue tint. 



Ouaiaretic Acid, C'"H"®0^ discovered by Hlasiwetz in 1859, may be 

 extracted from the crude resin by alcoholic potash or by quicklime. 

 With the former it produces a crystalline salt ; with the latter an amor- 

 phous compound : from either the liquid, which contains chiefly a salt 

 of guaiaconic acid, may be easily decanted. Guaiaretic acid is obtained 

 by decomposing one of the salts referred to with hydrochloric acid, and 

 crystallizing from alcohol. The crystals, which are soluble also in ether, 

 benzol, chloroform, carbon bisulphide or acetic acid, but neither in 

 ammonia nor in water, melt below 80° C, and may be volatilized with- 

 out decomposition. The acid is not coloured blue by oxidizing agents. 



By exhausting guaiacum resin with boiling bisulphide of carbon a 

 slightly yellowish solution is obtained (containing chiefly guaiaretic 



