Structural and Magneto-optic Rotation. 417 



might be expected that the resultant polarization would be 

 influential in determining the final form assumed. 



In the following experiments two coils, made of german- 

 silver wire carefully insulated by asbestos wrapping, furnished 

 at once the required temperature and magnetic field. The 

 coils were 160 mm long, with an opening into which a tube of 

 16 mm diameter would snugly fit. They were composed of four 

 layers of wire each containing forty turns, one end of each 

 layer being brought out so as to permit of connection in series 

 or in opposition, thereby making it possible to eliminate the 

 magnetic effect without altering the temperature. With the 

 current strength employed, which was from two to three 

 amperes, each coil, with layers connected in series, gave a cal- 

 culated magnetic field of between forty and fifty C. G. S. units. 



The determinations were all made in pairs : one in a mag- 

 netic, the other in a neutral coil ; and the period of heating 

 varied from two to four days for each experiment, this being 

 the limit set by the unavoidable carbonization which, if carried 

 too far, detracts from the delicacy of the polariscope reading ; 

 while the incidental evolution of carbonic acid results in such 

 an increase of pressure that, though the tube should withstand 

 it, partial loss of contents by violent effervescence upon open- 

 ing the tubes is inevitable.* 



As a rule the tubes contained 5 grms. of dextrotartaric acid 

 with 3 cm3 of water and, in order to reduce the pressure by 

 expelling the air, were sealed while the contents boiled. At 

 the conclusion of the experiment the tubes were emptied into 

 50 cm3 flasks, from which the portions tested were filtered into 

 the polariscope tube. 



Preliminary tests seemed to indicate a slight influence point- 

 ing toward a tendency of the molecules under these conditions 

 to group in the same way, that is to produce one product more 

 abundantly than the other. 



In order to determine certainly whether or not this effect 

 was invariable, a series of some twenty determinations was 

 made under carefully regulated conditions. The quantities of 

 tartaric acid were accurately weighed and the water measured 

 with equal care. To avoid any possible effect due to difference 

 of pressure each pair of tubes was exhausted by a water pump 

 and sealed off at the same instant and at the same length. 

 The temperature of the two coils was accurately equalized, 

 each being then protected from loss by radiation by means of 

 loose coverings of asbestos and finally enclosed in the same 



* It may be worth observing that the glass tubes thus employed have so 

 yielded to the pressure at the temperature of these experiments as to make their 

 further use impossible, unless perchance reannealing should restore their strength. 

 The glass, however, did not appear to be chemically acted upon as it is by pure 

 water when heated to that temperature. 



