CHEMICAL SELECTIOX OF MOTHERS. 117 



tube does not fill rapidly, or the funnel does not empty 

 itself, the difficulty may be overcome by slightly 

 increasing the slant of the tube, by raising the funnel. 

 If the flask is too low, there is danger of siphoning 

 the tube; the funnel is then lowered. Precaution must 

 be taken to have the curved glass tube, at the empty- 

 ing extremity, of a suitable length. When the day's 

 observations are finished, the tube should be washed 

 with distilled water and kept full until again used; then 

 the washing should be done with acidulated water and 

 a saccharine liquor of about the same strength as the 

 sugar solution to be analyzed. 



j\I. Pellet recommends that the washing be done 

 in another room from where the polarizations are to be 

 carried on. The reason being that the difference of 

 temperature of the water used and the room would 

 be sufficient to leave traces along the inner surface of 

 the tube, which might alone be sufficient to influence 

 the results. For washing the tube before using, it js 

 proposed to use the liquid from the flask, K (Fig 43), 

 which may be considered as an average for the day's 

 observations. This funnel continuous-tube attachment 

 may be applied to any polariscope, but should be made 

 to exactly suit the requirements. The space necessary 

 is about 25 to 30 m. m. greater than would be needed 

 for an ordinary tube. 



Continuous Polarization. 



In beet-seed selecting laboratories, the Pellet con- 

 tinuous tube for polariscope has been a most important 

 innovation. By the use of a polariscope and an ordi- 

 nary observation tube, in the hands of an expert, 1000 

 readings have been made in twelve hours. Several 

 assistants are frequently needed to accomplish these 

 results, since about 50 such tubes are riecessary. These 

 have to be carefully filled, screwed together, emptied 

 and washed; frequent accidents occur and the item of 



