38 



nued evaporation the lowering of the boiling-point becomes snuiller 

 and smaller, soon passes tlirongh zero, and then becomes a rise of 

 the boiling-point. This phenomenon shows that a more volatile 

 component with lower boiling-point is formed in the methylrhoda- 

 nide, and that the vaponr is mnch richer in this component than 

 the coexisting liqnid, so that tliis new component can easily be 

 expelled on prolonged evaporation. 



That nnder these circumstances the lowering of the boiling-point 

 of the substance under in\'estigation is tinally replaced by a rise of 

 the boiling-point is easy to understand, as the licpdd contained dis- 

 solved Cdl2. 



That tlie /irst experiment with the first bnlb yielded 123°6, and 

 that with the second bnlb 124°. 8 is owing to this that more vaponr 

 escaped from the second bnlb than from the tirst bnlb before the 

 first determination was made. 



Finally we undertook the chemical investigation of another part 

 of the same liqnid. This chemical investigation consisted in this that 

 we examined whether mustard oil had formed in this liquid. In 

 order to do this we boiled the liquid with dilute sulphuric acid in 

 a flask which was closed by means of a pierced cork with a long 

 glass tube. It is known that in the presence of mustard oil H^S is 

 formed nnder these circumstances, which can be immediately demon- 

 strated by means of a lead-acetate paper laid on the month of the 

 long glass tube. The result was a very clear hydrogen sulphide reac- 

 tion, which quite failed to appear in the investigation of the "pure" 

 methylrhodanide M, which was a conclusive proof that the lowering 

 of the boiling point is accompanied with the formation of mustard 

 oil, so that it is all but certain that the peculiar phenomenon which 

 was observed for the tirst time by Walden must be ascribed to the 

 formation of this substance, and that when the substance behaves 

 as a unary one we shall have to do with the following internal 

 equilibrium. 



CH^SCN ^ CH3NCS. 



It is clear that if on continued investigation the above equilibrium 

 really appears to exist, we have again a very interesting system 

 here, wliich urgently calls for further investigation. This will cer- 

 tainly be taken in h.and ; tirst of all the pseudo-system methylrhoda- 

 nide-methyl mustard oil will be examined, and then by means of 

 catalysers the situation of the unary system \vill be determined in 



^) Probably this contains also a trace of mustard oil, which in the experiment 

 escapes the action of the H3SO4. 



