440 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



expense of the ice saved, and a beer of superior quality pro- 

 duced. 6 B, November 17, 1873, 1140. 



DETECTION OF PICRIC ACID IN BEER. 



The method for detecting picric acid in beer, suggested by 

 Pohl, according to Brunner, will indicate the presence of one 

 sixty-fifth of a grain of the acid in a pint of beer, if conduct- 

 ed as follows: Immerse a piece of white woolen yarn in the 

 beer, acidified with hydrochloric acid, on a water-bath. Since 

 extractive matter will be precipitated by picric acid, and will 

 impart a dirty, brownish-yellow coloration to the yarn, treat 

 the latter with warm dilute ammonia water, which will ex- 

 tract all the picric acid; filter, and concentrate the solution 

 on a water-bath to a small volume, and add a few drops of 

 cyanide of potassium. The smallest trace of picric acid will 

 be indicated by a red coloration, due to the formation of iso- 

 purpurate of potassium. 5 (7, 1873, xlv., 360. 



DETECTION OF FOREIGN BITTER PRINCIPLES IN BEER. 



The following method for the detection of alkaloids and 

 other poisonous substances and bitter principles in beer, em- 

 ployed by DragendorfF, is also followed by Kubicki, on ac- 

 count of its simplicity and inexpensiveness. The liquid to be 

 investigated was evaporated on a water-bath to the consist- 

 ency of sirup, 3 to 4 times its volume of 85 per cent, alcohol 

 was then added, and the whole allowed to remain, without 

 heating, for 24 hours, in order that the gum, dextrine, albu- 

 men, etc., might separate. It was then filtered, and the alco- 

 hol was completely distilled oiF. The residual liquid was al- 

 lowed to rest, after cooling, for 10 to 20 hours, for the separa- 

 tion of any residue of the above substances, and then filtered. 

 The filtrate was acidified with dilute sulphuric acid, and 

 shaken for half an hour with about \ to \ its volume of pe- 

 troleum naphtha, then poured into a burette having a glass 

 stop-cock ; and after complete separation of the liquids, by 

 standing, the aqueous portion was drawn off* for further treat- 

 ment, and the petroleum carefully washed with distilled 

 water to free it from any adhering portions of the aqueous 

 liquid, then filtered, and the filtrate evaporated without the 

 aid of heat. The object of this was to prevent the loss of cer- 

 tain volatile substances, and, if possible, to obtain the peculiar 



