30 BATES AND JACKSON: QUARTZ-WEDGE SACCHARIMETER 



From the data on the rotation of the normal solution for 

 X = 5461 A and the latter ratio, the value for X = 5892.5 A was 

 computed to be 34?617 at 20? 



For X = 5892.5 A the normal plate has 0?003 greater rotation 

 than the normal solution, while for X = 5461 A it has 0?073 

 lower rotation. The rotary dispersion curves of the plate and 

 solution thus cross at about X = 0.585 /*. 



The slight differences between the rotary dispersions of quartz 

 and of sugar cause differences in the saccharimeter readings when 

 illuminated by various light sources. If, instead of the Wels- 

 bach mantle the saccharimeter is illuminated by the source 

 X = 5892.5 A the calculated reading would be 99?99 S. ' 



The normal solution causes a rotation of wave length 5461 A 

 which is by calculation 0.19 2 S higher than that of wave 

 length 5892.5 A. Experimentally the difference was found to 

 be 0?18 B £. 



By combining data of two previous investigators on the rota- 

 tion of quartz 1 mm. thick with our values for the rotation of 

 the normal plate, the thickness of the latter is found. This 

 calculation yielded the two values 1.5934 mm. and 1.5940 mm. 



The measurements of the rotations of the normal solutions 

 for monochromatic light, afforded sufficient data for the exact 

 calculation of the specific rotations since rotations, length of 

 solution, and concentration were accurately known. The 

 following values were obtained: 



Mx°i 5 892.5^66?529 



K n f 54 Gi ^=78?342 



The mean of the best previous determinations of the specific 

 rotation of the normal solution for X = 5892.5 A is 66? 502 with 

 which our value is in substantial agreement. On the other hand 

 Schonrock calculated the specific rotation from the conversion 

 factor 34? 657 and the saccharimeter reading of the normal solu- 

 tion for X = 5892.5 A. This gave for the rotation of the nor- 

 mal solution 34? 667 and the specific rotation 66? 627 which value 

 is considerably too high. Our own value of the specific rotation 



