CHEMICAL SELECTION OF MOTHERS. 83 



sponds to 12 per cent, sugar. If this volume of the 

 invert-sugar solution is required to discharge the blue 

 color of ID c. c. of the Violette reagent, the beet is not 

 suitable for a mother and is rejected. 



General Remarks Respecting the Method. 



The boiling of juice with acids demands consider- 

 able care, and should be watched from the start, as the 

 surface fro~thing is excessive. To obviate, in a meas- 

 ure, this difficulty, it is proposed to add the acid only at 

 the end of the boiling. Then again, some chemists 

 recommend that acetic instead of sulphuric acid be 

 used, under which circumstances, at least lo to 15 c. c. 

 are needed. There is always a danger of the sulphuric 

 acid combining with substances other than sugar; con- 

 sequently, it is an evident mistake to bring the acid in 

 direct contact with the beet slices.* The juice and 

 acid lead to the best results. Even in this case; there 

 are sources of error, as beet juices always contain a 

 substance very like glucose, which has, itself, an influ- 

 ence on the copper solution which evidently forces the 

 results; under the best of circumstances, the A'iolette 

 method is only approximative. 



Another objection to the method is, that artificial 

 light cannot well be used; the expense of chemicals, 

 gas, etc., are items not to be overlooked when seriously 

 undertaking laboratory selection on a large scale. 

 Furthermore, looking at the method from a practical 

 standpoint, it is entirely too intricate and leads to the 

 best results only in the hands of experts, who should 



•M. Pellet savs tlie action of the acid on tissiips of tlie beet may be 

 avoided in working .ts follows: Divide the operation in two parts; 

 make np with iliebeet and boiliTig wafer a volnnie of 200 c.c., from 

 ■which is taken 100 c.c. of jnice. After filtrntion and decantation, in- 

 Tert with snlphnric acid and dilute until the volume is 200 c.c. ; conse- 

 qnently, there are 10 grams of beets in 400 c.c. These manipulations 

 are tedious and do not avoid the errors, which may be 0.2 to 0.7 per 

 cent, in certain beets not having attained tlieir fnll maturity, or even 

 1 to 1.6 per cent, in beets of inferior quality, or which had undergone 

 changes during keeping. 



