PURITY OF ALCOHOL 103 



ing for four hours or longer indicates the pres- 

 ence of molasses alcohol. Neither domestic nor 

 foreign alcohols respond to this test. 



10. Pass hydrogen sulphide gas through 20 

 c.c. of the alcohol for from two to five minutes, 

 then add a few drops of ammonia and allow to 

 stand for four hours. The alcohol should re- 

 main colorless. If it becomes yellowish or 

 brownish, the presence of traces of metal, ex- 

 tractives or tannin is indicated. By this test 

 many of the samples of imported alcohol are 

 shown not to be up to standard. 



11. To 10 c.c. of the alcohol add 1 c.c. of a 

 solution of potassium permanganate (1-1000). 

 Allow to stand twenty minutes, the develop- 

 ment of a yellowish or brownish color indicates 

 the presence of aldehyde. Many of the im- 

 ported alcohols show this impurity in more 

 than traces. Our redistilled alcohol does not 

 show it. 



12. To 5 c.c. of the alcohol add two drops of 

 a one per cent aqueous solution of furfurol, un- 

 derlay this, kept cold in a stream of water, with 

 5 c.c. of sulphuric acid. The formation of a 

 colored zone, gradually becoming pink, shows 

 the presence of amylic alcohol. This is an ex- 

 ceedingly delicate test and by making a stand- 

 ard solution of amylic alcohol the proportion 



