22 ANALYSES OF SUGAR BEETS, 1905 TO 1910. 



Care must be exercised to prevent evaporation and changes of 

 temperature and also to use only a minimum amount of basic lead 

 acetate, generally nearer 3 cc than 5 cc, for clarification. By digest- 

 ing the beet pulp with the alcohol before extraction, the time of 

 extraction is greatly shortened, the pulp becomes thoroughly impreg- 

 nated with the alcohol, and all air is removed, resulting in a good 

 extraction of the whole material. If the pulp is fine and tends to 

 clog the siphon, alcohol-washed cotton may be used as a plug in the 

 extractor before adding the beet pulp, and a fine mesh screen may be 

 placed over the pulp to keep the whole compact in the extractor. 



To determine whether all of the sugar has been extracted or not 

 the following qualitative test is used: 



a-naphthol test for sugars. Add four or five drops of a 20 per 

 cent alcoholic <*-naphthol solution to a few drops of the alcohol 

 coming from the extractor and 2 cc of water contained in a small 

 test tube. Shake well, tip the test tube, and allow from 2 to 

 5 cc of colorless concentrated sulphuric acid to flow down the side of 

 tube; then hold the tube upright, and if sucrose is present a color 

 varying from a faint to a deep violet will be noted at the junction of 

 the two liquids. On shaking, the whole solution becomes a blue 

 violet color. This test is suitable for the results required of it in 

 this work, but it must be remembered that other sugars and sub- 

 stances besides sucrose give this color reaction. 



DISCUSSION OF METHODS. 



For a number of years the proper methods for determining sugar 

 in the beet have been discussed by sugar chemists, especially as to 

 the relative merits of alcohol and of water extraction. As a general 

 rule German sugar chemists favored alcohol methods, while the 

 French favored water methods. Within the last year a truce has 

 been declared and it is acknowledged that for very accurate or 

 control work the alcohol extraction method should be used, but for 

 general work, one of the hot-water digestion methods will give good 

 results and the analyst is less likely to introduce errors in the manipu- 

 lation. With the average sample of beets, the two methods when 

 carefully applied will yield duplicate results but in the case of very 

 abnormal beets one method might give higher figures than another. 

 The instantaneous methods (cold extraction) are only suitable 

 with very fine pulp and the results can be depended upon only when 

 they have been checked against a standard method. With these 

 instantaneous methods as many samples of beets can be analyzed 

 per day as by the indirect method, and it is claimed by many that 

 the Sachs Le Docte hot digestion method or the Herzf eld modification 

 will yield as many determinations in a given time as the indirect 

 method, with the same amount of work, provided the laboratory is 

 fitted for the work. 



