28 BATES AND JACKSON: QUARTZ-WEDGE SACCHARIMETER 



in which it was coupled with percentage of composition of solu- 

 tions. These two methods of determining the volume of solution 

 checked satisfactorily. 



The measurements of the absolute rotations of the solutions 

 were made on a large polarimeter with a silver scale reading to 

 thousandths of a degree. The temperature of the solutions was 

 controlled by an air bath placed between the polarizing and 

 analyzing systems of the instrument. It was cooled below 20°C. 

 by ice water and then heated electrically to 20°C. Regulation 



TABLE I 



Summary of Data on the Rotation op the Solutions 



was secured more closely than 0?05 C. The light source was the 

 so-called yellow-green line, X = 5461 A, from a quartz mercury- 

 vapor lamp. 



Three different makes of saccharimeters were used in order to 

 eliminate the possibility of some peculiarity of instrument con- 

 struction affecting the measurements. They were a Bates type 

 Fric, a Schmidt and Haensch, and a Julius Peters. Two instru- 

 ments were used in each experiment, one of which was always 

 the Bates type Fric. It was enclosed in a wooden thermostat 

 with automatic temperature control to within a few hundredths 

 of a degree. The saccharimeter readings were made in a large 



