12 McBAIN 



common, that Luther has come to the conclusion that it is not 

 worth while discussing whether Kohlrausch's Law is strictly 

 quantitative or not until the experimental data are more reliable. 



QUALITATIVE EXPERIMENTS. 



Qualitative or semi-quantitative experiments are sufficient to 

 show whether a given component of a solution moves toward 

 the anode or toward the cathode during electrolysis. In order 

 that the results may be decisive as to the constitution of the 

 solution, however, further experiments must be made to find 

 whether or no the component in question is present in colloidal 

 form ; this has been done in recent papers from the Leipsic 

 laboratory. 



If the experiment is carried out by electrolysing the solution 

 between two other " electrode solutions," the presence of one 

 of the components of the intermediate solution in the cathode 

 compartment may justly be regarded as evidence that the com- 

 ponent in question formed a constituent of some cation ; the 

 converse, however, is not necessarily true. It is possible that 

 the component which in the intermediate solution formed part 

 of a cation might have acted as anion in the cathode solution, 

 and that it was consequently, in large part at least, driven out 

 as soon as it entered. The experiments of Richards and Bonnet 

 in 1904, and of Lind in 1903, offer a case in point; the authors 

 are however doubtless justified in the conclusions which they 

 draw, for the rate of transformation of the various modifications 

 of chromic sulphate into each other is notoriously slow. 



ARRANGEMENT OF THE ABSTRACTS, ABBREVIATIONS USED. 



In the following abstracts general information is given in a 

 paragraph which does not require further explanation. In the 

 tables, the first column gives the chemical measured ; the sec- 

 ond the concentration (m denotes mols, that is gram-formula- 

 weights) ; the third the temperature ; the fourth the number of 

 grams of silver or copper deposited in the voltameter, indicated 

 by the abbreviation " g Ag," *' g Cu," etc. ; the fifth the per- 

 cent change in the composition of the middle (supposedly unal- 

 tered) portions, calculated by myself; the sixth, the number of 

 experiments (" ex ") ; the next indicates which electrode solution 



