FERMENTED AND DISTILLED LIQUORS. 81 



23. DETECTION OF STARCH. 



First destroy the color of the jelly by treatment with sulphuric acid and potassium 

 permanganate and then test with iodin. Bring the solution of jelly nearly to the 

 point of boiling, add several cubic centimeters of dilute sulphuric acid and then 

 potassium permanganate until all color is destroyed. By this treatment the starch 

 remains unaffected. The test for starch is not necessarily an indication of its addition 

 as an adulterant. It is almost always present in the apple, and occasionally in other 

 fruity, and unless it is present in the jelly or other fruit product in considerable 

 amounts it may be due to that source. 



24. DETECTION OF GELATIN. 



The presence of gelatin in jellies and jams is shown by a higher content of nitrogen. 

 Precipitate a concentrated solution of jelly or jam with 10 volumes of absolute alcohol 

 and determine nitrogen in dried precipitate by the Gunning method. a 



25. DETECTION OF AGAR AGAR." 



Cook the jelly with 5 per cent sulphuric acid, add a crystal of potassium perman- 

 ganate and allow to settle. If agar is present the sediment will be rich in diatoms, 

 which can be detected by use of microscope. 



26. THE DETERMINATION OF HEAVY MKTALS. 



Treat 100 grams of the preserve directly in a large porcelain evaporating dish with 

 sufficient concentrated sulphuric acid to thoroughly carbonize the mass. If much 

 water is present evaporate the material to a sirupy consistency before treating with 

 the acid. From 15 to 25 cc of strong acid has been found sufficient to thoroughly 

 carbonize the amount specified. Then ash the material, transfer the ash to a beaker 

 of about 400-cc capacity, slightly acidify it with hydrochloric acid, and boil for a few 

 moments. Methods for separation and determination of metals are given on page 52. 



XIV.-FERMENTED AND DISTILLED LIQUORS. 



By W. D. BIGELOW, 

 In charge of Food Laboratory, Bureau of Chemistry, U. S. Department of Agriculture. 



(A) WINE. 



The determinations of most value in judging the purity of wine are alcohol, gly- 

 cerol, extract, ash, total and volatile acids, and reducing sugar. The actual percent- 

 age of these substances present is of interest, but much more important are certain 

 relations between them, such as ash to extract, extract to alcohol, alcohol to glycerol, 

 alcohol to acids, and volatile acids to total acids. Examination for preservatives and 

 foreign coloring matter must also be made. Search is sometimes made for lead, which 

 may result from cleansing bottles with the aid of shot; for copper and arsenic, which 

 sometimes result from the use of insecticides and fungicides on the grapes; and for 

 barium and strontium, which are sometimes used in southern Europe to remove the 

 excess of sulphate introduced by plastering. A qualitative test is often made for 

 nitrates to detect the addition of (impure) water, and for dextrin to determine 

 whether glucose has been used in the preparation of the wine. 



Information regarding the manner of preparing the wine is often afforded by the 

 determination of tannin, potassium sulphate (for plastered wines), and of phos- 

 phoric acid. 



A. Boemer, Chem. Ztg., 1895, 1, 552. 



*>C. Marpmann. Ztschr. f. angew. Mikrosk. 1896, 2, 260. 



Hi-48 No. 6502 6 



