366 C4IBBS. 



dissolved in a very small quantity of water containing just enough 

 potassium hydroxide so that the resulting solution is almost neutral, a 

 copious precipitate of the steel-blue crystals of coeriilignon is obtained 

 on adding a drop of the hydrocoerulignon reagent. If the solution be- 

 comes too alkaline through the addition of too much caustic alkali it 

 can be made acid with acetic acid before the addition of the Liebermann 

 reagent. An aqueous solution of phenoquinone will also give this reaction 

 for quinone, the coerulignon crystals being very characteristic. This 

 is to be expected from the fact that phenoquinone is a compound of 

 very slight stability.-^ 



Hydrogen peroxide has been found to react with hydrocoerulignon, 

 producing the characteristic coerulignon crystals. The samples of red 

 phenol which were found to react with the hydrocoerulignon reagent 

 were tested for hydrogen peroxide and while traces were indicated by 

 both the vanadic acid and the titanic acid reactions, the amounts seem to 

 be too small to account for so great an oxidation of hydrocoerulignon. 

 Any considerable amount of hydrogen peroxide would hardly be ex- 

 pected to be present if it reacts with the phenol to produce oxidation 

 products. 



One cubic centimeter of red phenol dissolved in about 15 cubic 

 centimeters of water will liberate iodine from the potassium iodide 

 reagent (potassium iodide dissolved in water with or without the 

 addition of a little ferrous sulphate) as shown by the addition of starch 

 solution. The blue color does not appear at once for the reason that 

 the phenol reacts with the first portions of iodine set free. After some 

 minutes, however, the blue starch compound is unmistakably present. 



Another method which is in some respects more satisfactory for 

 producing the reaction, is the addition of 1 cubic centimeter of the red 

 phenol through a pipette reaching to the bottom of a test tube containing 

 the solution of potassium iodide and starch, with or without a trace of 

 ferrous sulphate. Immediately above the red layer will appear the 

 starch-iodine blue. On gently rotating the test tube the blue starch 

 compound will float upward, through the colorless reagent. Colorless 

 crystals of phenol will not produce this reaction. While quinone will set 

 iodine free from a solution of potassium iodide its presence is not 

 conclusively proved by this test for the reason that the hydrogen peroxide 

 which may be present will produce the same reaction. 



If the theory that the red color is caused by a phenol solution, or 

 condensation of the oxidation products of phenol, principally quinone, 

 is correct, phenol in dilute solutions under the same conditions of 

 moisture, oxygen, and light rays should be oxidized and the solutions 

 should be colored only by these oxidation products. Mixtures of the 



-' Jackson and Oenslag;er, loc. cii. 



