THE RED COLOR IN PHENOL. 369 



do not react with each other in the presence of sunlight to form oxygen 

 or hydrogen peroxide and other products according to the von Baeyer 

 assimilation hypothesis. Bach,'"' however, states that he has produced 

 this decomposition in the presence of uranium acetate by passing the gas 

 into a solution of the salt in the sunlight, obtaining formaldehyde 

 and hydrogen peroxide as the products. Euhler"^ severely questions 

 these results. The decomposition of carbon dioxide in the presence of 

 water has been effected by Lob'^ by means of the silent electric discharge, 

 the products being carbon monoxide, oxygen, hydrogen peroxide, formic 

 acid, and formaldehyde. It would thus appear that the reaction between 

 carbon dioxide and water requires the presence of a more powerful 

 catalytic agent than sunlight. From the work of Kastle "'^ and others, 

 it is evident that the presence of phenol, a peroxidase accelerator, would 

 have a beneficial effect upon such a reaction when once it is started. 



CRITICISMS OF SOME OF THE EARLIER WORK. 



While it may be possible that some of the impurities in phenol such as 

 ammonia, tliiophene, creosol, parakresol, etc., may cause a discoloration 

 as stated by Miiller, Sicha, Meyke, Ebell, Hager, Kremel, Mylius, Fabini, 

 and Bidet ; impurities, other than moisture and oxygen, do not cause the 

 coloration of pure phenol. The oxygen of the atmosphere was thought 

 by Hager and Ebell to produce the red color through i1g effect upon the 

 impurities present and not upon the phenol itself. Fabini, while he 

 ascribes the action to hydrogen peroxide, also considers that impurities 

 such as metallic salts and ammonia must be present. 



Although Kohn and Fryer, and later Richardson, proved the cause of 

 the coloration to be hydrogen peroxide, the explanation of the mechanism 

 of the reactions involved is not entered into by them, except that the 

 former hint at the possibility of an indophenol being present. The 

 experimental proof upon which Bach bases his criticism of the work of 

 Kohn and Fryer must be inaccurate. When he attempted to exclude 

 oxygen by working in an atmosphere of carbon dioxide it is highly 

 probable that he did not rigidly accomplish the desired result, or else 

 other impurities were present. 



Because Bach failed to find hydrogen perozide in the mixture of 

 phenol, water, and carbon dioxide it can not be considered proved that 

 available oxygen was not present to react with the phenol. It is very 

 improbable that rosolic acid, corallin, or tropa^olin as suggested by Hager 

 have produced the color in the samples of phenol investigated by him. 



^Ber. d. chem. Ges. (1894), 27, 340. 



"^Ibid. (1904), 37, 3414. Bach's answer, Ibid (1904), 37, 3985; (1906), 

 39, 1672. 



'"Ztschr. f. elek. Chem. (1906), 12, 282. 

 ="Am. chem. Jour. (1908), 40, 251. 



