208 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



rated from the mother liquors containing the liquid tar acid 

 and a residue of carbolic acid dissolved in them. Complete 

 purification of the carbolic -acid crystals thus obtained is 

 eflected by recrystallization, either by partial fusion or solu- 

 tion in water, with subsequent refrigeration. Carbolic acid 

 of high degrees of purity is obtained by dehydrating these 

 carbolic-acid crystals. Practical Magazine^ Dec.^ 1874, 437. 



DETECTING ADULTERATIONS IN COFFEE. 



Wittstein, in a paper published in " Dingler's Polytechnic 

 Journal," gives a detailed method for testing coffee, which is 

 treated in a great variety of ways for the purpose of impart- 

 ing^ o;reater strens^th or weio^ht, a better color, or some other 

 desired quality. He remarks that roasting, and still more 

 grinding, cofiee renders it almost impossible to apply the 

 necessary tests. The principal vegetable substances used in 

 adulterating coffee are chicory, beet-root, carrot, figs, corn, 

 malt, etc. A simple method of testing coffee for a mixture 

 of chicory is to shake it with water; if pure it remains float- 

 ing for an hour together, whereas chicory sinks. An infusion 

 of burned chicory, diluted with much water and treated with 

 potassium bichromate, undergoes no visible change ; but 

 coffee assumes a deejD brown tint, causing a resemblance to 

 porter. This is only observed, however, Avhere the substance 

 is either entirely coffee or entirely chicory. To detect a 

 mixture of the two, the decoction is diluted with eight times 

 its bulk of water, filtered, and the dilution increased to twelve 

 parts. If the decoction contains pure coffee, on adding to 

 thirty drops of it two drops of concentrated hydrochloric 

 acid, boiling for a few seconds, then adding fifteen drops of a 

 solution of one part of potassium ferrocyanide in eight i3arts 

 of water, and boiling as before, the solution becomes first 

 green, then dark green. Six drops of potash are next added, 

 and the whole is boiled for two minutes, the solution becom- 

 ing first brown and then clear pale yellow, with a slight 

 dirty-yellow precipitate. With chicory alone, the solution 

 finally remains brown and turbid, and after long standing a 

 precipitate falls, the supernatant fluid retaining its brown 

 color. With a mixture of twent3^-four drops of coffee and 

 six of the chicory decoction, a final brown turbid solution is 

 obtained. A decoction of coftee of averacce streno-th contains 



