CHEMICAL SELECTION OF MOTHERS. 85 



sible indication of what the conditions are. The quan- 

 tity of pulp to be weighed is either 16.29* grams or 

 26.048 grams, according to polariscope used. This 

 sample is placed in a vertical tube over a fliask in which 

 alcohol is being boiled. The vapors of alcohol falling 

 upon the beet pulp will carry back to the flask the 

 sugar dissolved; as the evaporation goes on, the siigar 

 solution becomes denser and denser, and ceases when 

 the pulp has been entirely exhausted of its sugar. The 

 usual polarization follows. By the German polariscopes, 

 one knows in one reading what the sugar percentage 

 is. If it is found necessary to make a large number 

 of analyses at one time, the Soxhlet appliance may be 

 arranged in the battery, and several flasks heated at the 

 same time to a temperature of 95 degrees C. Evi- 

 dently, the great objection to any of these appliances 

 based on the alcohol method of extraction, is that the 

 operation must always be repeated in order to obtain 

 accuracy in the final results. Another source of error, 

 unless in expert hands, is the danger of adding an 

 excess of sub-acetate of lead, which chemical, according 

 to Pellet, has a tendency when in the presence of alco- 

 hol to diminish the rotatory power of sugar, or even in 

 certain cases to precipitate a portion of it. There is 

 always a certain amount of alcohol lost, which adds 

 considerably to the expense. By all alcohol methods, 

 hot or cold, it is most essential to have the pulp in a 

 cream-like condition; otherwise, with all possible care, 

 the sugar percentage will be less than the reality. 



(b) Hot and Cold- Water Methods. f 



The hot and cold-water methods for the analysis 

 of samples of beets have of late years undergone many 



*At the coTigress of cljemists lield in Paris duriTiff 1896. it was con- 

 cluded that the weight for French polariscopes should be 16.29; this 

 has yet to be officially accepted, but we have adopted it. 



t We have not nsed the term aqueous for the simple reason that 

 t)ie word isnot altosetlier in keeping witli the general practical style 

 of tlie present writing. * 



