was produced by the acacia and guaiac. He also records the fact 

 that certain toothache remedies containing resin of guaiac colored 

 the mouth blue or green, and, from experiments with albuminous 

 substances, concluded that the color was produced by the albumen 

 in the saliva and the guaiac. 



Planche" in 1810 observed that pieces of certain fresh roots 

 colored tr. of guaiac blue, also that nearly the same effect was 

 produced by sulphurous acid gas and tr. guaiac. 



In 1819 Taddey 19 observed that corn meal and powdered 

 resin of guaiac when mixed with water and exposed to the air 

 became blue. 



Rudolphi 19 found that in the above mixture the color was 

 produced by gluten and guaiac. 



Planche 20 in 1820 gives a list of about 25 plants, the fresh 

 roots of which give a blue color with tincture of guaiac, and states 

 that fresh milk not boiled produces the blue color with tr. guaiac. 

 He was the first to discover that the power of albuminous sub- 

 stance to produce the blue color with tr. of guaiac was destroyed 

 by heat. He experimented upon the action of light and air, suc- 

 cessively examined and rejected the intervention of oxygen, but 

 concluded that action was due to a kind of undetermined cyano- 

 gen. 



Schonbein 21 in 1856 observed that the juice of certain mush- 

 rooms, Boletus luridus and Agaricus sangnincns, colored tincture 

 of guaiac blue but lost their power when heated to 100 C. In 

 1868", he reports that the blue color is formed by ozone, pro- 

 duced by a kind of catalytic action. He arrives at this conclu- 

 sion after a series of experiments with the fresh juice from 

 plants, and tincture of guaiac, under varying conditions of light 

 and air, and with oxygen obtained from other sources. 



In 1872 Struve 23 made some experiments upon the change of 

 pyrogallol to purpurogalline by acacia, saliva and other substances 

 which produced a blue color with tinct. of guaiac, but did not 

 arrive at any definite conclusions as to the true action. 



In 1877 Traube 24 divided ferments into two groups : a. Oxi- 



18 Bulletin de Pharmacia t. II. p. 579, 1810. 



18 Journal de Fisice Chim. etc. 2d. Semestre, 1819. 



' M Journal de Pharmacie t. VI. 1820, pp. 16-25. 



!1 Jour, fur Prakt. Chem. 67, 1856, 496. 



"- Jour, fur Prakt. Chem. 105, 1868, p. 198. 



23 Ann. d. Chem. u. Pharm. 163, 1872, p. 160. 



" 4 Ber. d. Chem. Ges., 10, 1877, p. 1985. 



