GUAIAC 361 



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 benzoin. It 

 is readily soluble in ether, alcohol, chloroform, solutions of the 

 alkalies or hydrated chloral. It is sparingly soluble in benzol, fixed 

 or volatile oils. The alcoholic solution has a brown color, which is 

 changed to blue by the addition of solutions of ferric chloride, or 

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

 chlorin, bromin or iodin. An alcoholic solution of guaiac is colored 

 blue by enzymes. The blue color is destroyed on the addition of 

 reducing substances. 



The powder when examined under the microscope shows numer- 

 ous lemon-yellow or dark-brown resin masses, which when mounted 

 in solutions of hydrated chloral are wine-colored at the margin; 

 few fragments of tissues with characteristic sclerenchymatous cells 

 and fibers; few crystals of calcium oxalate in monoclinic prisms. 



Constituents. Several acids are present, including guaiaconic, 

 guaiaretic, guaiacresinic, guaiacinic, and guaiacic. Guaiaconic 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 investi- 

 gations show that guaiaconic acid consists of two crystalline sub- 

 stances: a-guaiaconic acid and /3-guaiaconic acid. The latter crys- 

 tallizes 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 having a 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 alka- 

 lies. Guaiacresinic acid occurs in white, shining plates that are 

 soluble in alcohol and give on dry distillation the same products as 

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

 brown powder and yields on dry distillation tiglic aldehyde (dimethyl 

 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 con- 

 tains a yellow coloring principle, guaiac yellow (about 0.7 per cent), 

 which occurs in light yellow, hard octahedra that are sparingly sol- 

 uble in hot water and give a blue color with concentrated, sulphuric 



