35 



naturally led to expect the same for methjh'lioclaiiide, and it was 

 now naturally supposed tliot the methylrhodanide, as it is obtained 

 in the preparation, is not yet in internal equilibrium, and that the 

 lowering of the boiling point or the increase of the vapour tension 

 which occur, are a consequence of the setting in of the internal 

 equilibrium which is possibly reached with appreciable velocity under 

 the influence of the said salts. These salts would therefore be catalysts. 

 Now it is known that in sealed tubes heated to 180° methyl- 

 rhodanide is partly converted to the isomer methyl mustard oil ^). 

 We have here an intramolecular atomic shifting 



S — CeeeN N = C = S 



As methylrhodanide boils at 130,5° and the isomer, the mustard oil 

 at 119°, this con\'ersion when accelerated by the said salts, might give 

 rise to a lowering of the boiling point resp. increase of vapour tension. 



This consideration led us to the supposition that the internal equi- 

 librium which was mentioned just now, might be an equilibrium 

 between the isomer molecules CH3SON and CHgNCS 



CH,SCN :^ CH3NCS. 



Before we now proceeded to test this supposition, the difference 

 of vajiour tension between pure methylrhodanide and a saturate 

 solution of Cdlj in methylrhodanide was examined at different tem- 

 peratures in a small tensimeter, in which mercury was used as the 

 liquid measuring the tensions. 



It was remarkable to see that in the first moments the saturate 

 Cdl^-solution possessed a smaller vapour-tension, but soon the diffe- 

 rence of vapour tension passed through zero, and then obtained the 

 opposite sign. At 25° the position of the mercury manometer appeared 

 not to change any more after a fortnight, and the increase of vapour 

 tension amounted to 11,2 mm. Hg. The same experiments were also 

 made at higher temperatures, ' and, as was expected, they gave a 

 greater difference of vapour tension as result. These were, however, 

 less reliable quantiratixely, because mercury seems to have analysing 

 power at higher temperatures. Accordingly glass-spring manometers 

 will be used to obtain more accurate results when the investigation 

 is continued. 



After it had thus appeared that by the addition of Cdl^ after a 

 transient decrease of vapour tension actually an increase of vapour 



1) For allylrhodanide conversion lo nnislard oil alicady takes place after distil- 

 lalion under atmosphei'ic pressure. 



. 3* 



