Pentose, Formaldehyde and Methyl Alcohol 449 



224 (2184) 



Concerning the detection of pentose, formaldehyde and 

 methyl alcohol. 



By JAMES B. SUMNER. 



[From the Departments of Physiology and Biochemistry, Medical 

 College, Cornell University, Ithaca, N. Y.] 



Bial's reagent, as ordinarily made up, does not keep. It is 

 better to dissolve the orcinol and ferric chloride in alcohol, (6 gm. 

 orcinol, 40 drops ferric chloride in 200 c.c. alcohol). Heat 5 

 c.c. of sugar solution with 15 drops of the above and an equal 

 volume of fuming hydrochloric acid. A blue color develops if 

 pentose is present. 



When formaldehyde is subjected to this test a white precipi- 

 tate is formed if 0.1 mg. per c.c. is present. Upon heating the 

 precipitate turns brown. Acetaldehyde gives a precipitate 

 which does not turn brown. With minute quantities of formal- 

 dehyde there is no precipitate but if the test is made strongly 

 alkaline a strong green fluorescence is observed. 



Orcinol can be used to detect methyl alcohol as follows : 



Distill off the alcohol, using a Vigreux column and allowing 

 as little water to pass over as possible. Place 1 c.c. of the dis- 

 tillate in a large hard glass test tube, which is free from 

 scratches. Add 2 c.c. of 6.7 per cent, potassium dichromate solu- 

 tion and 2 c.c. of 62 per cent, sulfuric acid. Mix at once and 

 let stand for 10 minutes. Add 15 c.c. of distilled water, mix and 

 heat in boiling water for 10 minutes. Add 1 c.c. of a 0.5 per 

 cent, aqueous solution of orcinol. Mix well and continue the 

 heating for 30 minutes. If the original alcoholic distillate con- 

 tained 5 per cent, of methyl alcohol a heavy white precipitate 

 will appear after 5 minutes heating. With 0.5 per cent, methyl 

 alcohol a faint precipitate is formed after heating for 30 minutes, 

 or upon cooling. To show smaller quantities of methyl alcohol 

 add a slight excess of sodium hydroxide, heat for a few min- 

 utes and filter. The filtrate will show a green fluoresence if 

 traces of the methyl alcohol were present. Formic acid, acetone, 

 furfurol, amyl alcohol and acetaaldehyde do not interfere with 

 this test. Glycerine interferes if added to the distillate ; acrolein 

 interferes if present in considerable amount. 



