CRUDE DRUGS. 669 



reddish-brown and more or less transparent in thin pieces; fusible; 

 odor balsamic ; taste somewhat acrid. 



The powder of guaiac is of a grayish color, but becomes green 

 on exposure to the air, and on heating gives off an odor of ben- 

 zoin. It is readily soluble in ether, alcohol, chloroform, solutions 

 of the alkalies or chloral hydrate. It is sparingly soluble in ben- 

 zol, fixed or volatile oils. The alcoholic solution has a brown 

 color, which is changed to blue by the addition of ferric chloride, 

 or oxidizing agents (as chromic acid or ozone) or through the 

 action of chlorine, bromine or iodine. An alcoholic solution of 

 guaiac is colored blue by enzymes. The blue color is destroyed on 

 the addition of reducing substances. 



Constituents. Several acids are present, including guaia- 

 conic, guaiaretic, guaiacresin, guaiacinic, and guaiacic. GuAiAr 

 CONIC acid (alpha resin) occurs to the extent of 50 to 70 per 

 cent., and forms a brown powder which is insoluble in water, 

 soluble in alcohol and gives a blue color with nitric acid and other 

 oxidizing agents ; and on dry distillation yields guaiac oil and 

 pyroguaiacin. Recent investigations show that guaiaconic acid 

 consists of two crystalline substances : a-guaiaconic acid and 

 ^-guaiaconic acid. The latter crystallizes in rhombohedra and 

 does not give a blue color with oxidizing agents. When a solution 

 of a-guaiaconic acid in chloroform is treated with lead peroxide 

 GUAIAC BLUE is formed, which may be obtained as a blue mass 

 with metallic luster on evaporating the chloroformic solution. 

 On reduction with sulphurous acid it is changed to a-guaiaconic 

 acid. Guaiaretic acid (about 10 per cent.) occurs in 

 colorless needles and forms crystalline salts with the alkalies. 

 Guaiacresin acid occurs in white, shining* plates that are soluble 

 in alcohol and give on dry distillation the same products as guaia- 

 conic acid. Guaiacinic acid (beta resin) occurs as a yellowish- 

 brown powder and yields on dry distillation tiglic aldehyde (di- 

 methyl acrolein). Guaiacic acid forms colorless needles which 

 are soluble in water, but probably does not occur in the natural 

 product, being in the nature of a decomposition product. Guaiac 

 resin also contains a yellow coloring principle, guaiac yellow 

 (about 0.7 per cent.), which occurs in light yellow, hard octa- 

 hedra that are sparingly soluble in hot water and give a blue color 



