ClIEJIUAL SELECTIO-V OF MOTHERS. 119 



Analysis of Beet Juices in the Legras Laboratory. 



The polarization is unique, rapid, and most inter- 

 esting, two instruments being in constant use, and in 

 connection with them the Pellet continuous tube* is 

 employed. It, however, differs from the one just 

 described, and is known as the siphon method; it is 

 sho\\n in engraving (Fig. 44). The arrangement is 

 most simple, a rubber emptying tube at one end, and 

 at the other a covered glass tube with rubber attach- 

 ment. To the filtrates in glasses are added a few drops 

 of pure acetic acid; the glasses are carried to the sac- 

 charimeters in six Ijaskets of twenty compartments 

 each. The number assigned to the beet at the com- 

 mencement when it entered the laboratory is carefully- 

 continued through the entire series of manipulations 

 to which the samples, juices, etc., are submitted. 



The assistant places the rubber tube m one of 

 these conical glasses, precaution being taken to slightly 

 slant the glass, so as to give a greater depth of penetra- 

 tion to the juice. Cn the emptying tube is a Mohr 

 pinch-cock; this is opened when the chemist is ready 

 to make a new observation and the sugar solution is 

 siphoned into the continuous tube. The assistant 

 changes the glass for another with a fresh sample 

 before it is entirely empty; otherwise, there would be a 

 loss of time, due to the siphoning of all the juice in the 

 circuit. About eight observations may be made per 

 minute. Precautionary measures must be taken to 

 screen the observer's eyes from the brilliant light of a 

 lamp placed in front of the instrument; this excellent 

 arrangement is' shown fn the engraving. Under these 



*It nmst. never be lost sight of, that the continuous method requires 

 ureat care for its first working, that is to say. that the tubes with their 

 attachments must be made by a person thoroughly familiar with the 

 lequirements. Many mistal<es liave been made by depending upon 

 some contrivance furnished bv a novice; furthermore, the results may 

 vary with the chemist in cliarge, wlio had best make a preliminary 

 practice on sugar solutions of known strenstli. Tlie method Is most 

 excellent tor mother selection, and is recommended by Pellet for all 

 classes of polariscope work. 



