635 



§ 3. \n connection witli tliese data we can make the following 

 remarks. 



The substitution of the bromine in hroniohenzene by iodine, makes 

 the value of u at the same temperatures increase, just as we formerly 

 observed with the substitution of chlorine by bromine in the 

 cJilorohenzene. This behaviour is evidently opposite to what was 

 formerly stated in the case <"f the molten halogenides of the alcali- 

 metals. In agreement with our previons experiences, the substitution 

 of H 'm the benzene-nucleus by CH„ makes the value of fi increase 

 ihromobenzene and o-hroinotohume) ; and the same holds good for 

 the substitution of H by a A'^O^-group, by halogenides, or by the 

 r/co,i7/-radical ; in genei'al by substitution of H by radicals built up 

 from strongl}- electronegative atoms. This seems to be a general 

 rule. An analogous phenomenon is observed, if aromatic hydrocarbon- 

 radicals substitute the H-aionK : a comparison of the kexyl-, or 

 heptylamines with diphenijl-, and dibenzylainine makes this very 

 evident, and just in the same way a comparison of ncetophenone 

 and benzophenone. The fi-<-curve for ethylcinnamylate lies beneath 

 that for viethylcinnnmylnte, and the same is the case with mono- 

 inetbyhniUne in comparison with aniline itself. On the contrary, the 

 value of f« for aniline is very much increased by substitution of the 

 H of the amino-group by two isobutyl-vad\ca.\s. 



The addition of hydrogen in pyridine, this thus being transformed 

 into piperidine, makes the (t-^curve of the former compound fall ; 

 for thiophene it lies beneath that for piperidine. 



Some curves for ainylaniines are reproduced here also for the 

 purpose of comparison. This is connected on the OJie hand with the 

 substitution of the alom ' .S' ' in thiophene by tiie combination : 



— iV = CH — , and perhaps on the other hand with the presence of 

 the unsaturated f-atoms in pyridine, in comparison with tliose in 

 piperidine. However it must be remarked here at once, that evidently 

 this last may not be considered a general rule, as for instance the 

 curve of benzene lies lower than that for cyclohe.i:ane. Certainly 

 a number of constitutive influences are superposed one upon the 

 other, thus prohibiting the statement of the precise connection lietween 

 the value of ft and the degree of saturation of the C-atoms in this 

 case, to a more or less degree. 



We intend to finish here untill a later date the investigation of 

 organic compounds with the series here described. 



University Laboratory for Inorganic 

 (ivoniiujeii, August 1915. and Phy.tiral Chemistry. 



