36 



tension takes place, the tbllowing experiment was undertaken. A glass 

 vessel filled with methjlrhodanide and an excess of Cdl^ was exhausted, 

 and then kept for 6 weeks in a thermostat of 20°. 'fhen the vessel 

 was opened and the liquid investigated, in the first place as to its 

 boiling [)oint, and in the second place as to the formation of mustard oil. 

 Before we proceeded to the determination of the boiling point of 

 this liquid the boiling-point of the pure methylrhodanide used by 



us, was examined, by the exceedingly 



convenient method of Smith ^), which 



enables us to investigate extremely 



smajl quantities of substance. A tube 



of the shape indicated in fig, 1, is 



filled with the liquid which is to be 



rp^ I I I examined, then fastened to a thermo- 



/^\ f meter (fig. 2), and placed in a suitable 



v«X ^^m ^ V///j^ liquid bath, which is slowly heated, 



and vigorously stirred. At the boiling- 

 point a continuous stream of vapour 

 ^ 40 ^ ^^ bubbles escapes from the open end. 



If then the temperature is again 

 V\%. 1. Fig. 2. slowly lowered, the escaping of the 



vapour bubbles will suddenly cease as soon as the temperature has 

 fallen somewhat below the boiling-point. This point can be sharply 

 observed, and the experiment may be so often repeated till all the 

 substance has evaporated. 



As we used an oil-balh, and CHjSON easily dissolves in oil at 

 130°, we made the narrow tube a of the boiling bulb open into a 

 tube h which was ± 2 mm. wider. In this way we succeeded in 

 making the escaping vapour bubbles very clearly visible and prevented 

 that they immediately dissolved in the rapidly moving oil. 



When the experiment was repeated till almost all the liquid was 

 evaporated, the pure methylrhodanide gave the following result: 



1) Americ Chem. Soc. 32, 897 (1910). 



