47o SCIENCE PROGRESS 



The close agreement throughout the whole range of con- 

 centration of the two sets of a values is highly remarkable. 

 It is to be clearly understood that the values of a in the second 

 column are calculated indirectly on the basis that the true 

 degree of ionisation y is actually given by the conductivity- 

 viscosity ratio, whilst no such assumption is involved in the 

 data of Maclnnes and Parker. If the above agreement is con- 

 firmed by results with other substances it will afford proof that 

 the conductivity-viscosity ratio is a substantially correct measure 

 of ion concentration though not of ion activity. Unfortunately 

 sufficiently accurate freezing-point data are not available for 

 HC1 to enable corresponding computations to be made in the 

 case of this substance. Such data are much to be desired. It 

 will be observed that Ellis's conclusion does not bear out 

 G. N. Lewis's contention, viz. that the conductivity-viscosity 

 ratio is in error owing to the probability that the speed of 

 the ions increases as their concentration increases. Of course 

 so long as such changes are relatively small we are justified in 

 regarding the conductivity-viscosity ratio as substantially 

 correct. For KC1 this is fairly certain. For HC1 it is not yet 

 certain. 



INORGANIC CHEMISTRY. By C. Scott Garrett, D.Sc 

 Analytical. — The problem of quickly providing a supply of 

 water for drinking and culinary purposes is one which is of 

 almost daily occurrence in these stirring times. For armies in 

 the field, for troops in fresh training grounds, for munition 

 factories planted out in the wilds, sea-borne supplies for 

 expeditions or for fleet units, this provision of sterilised water 

 is an urgent problem . As a rule the simplest and most effective 

 method of sterilisation is by the addition of a small quantity of 

 chloride of lime, calcium chloro hypochlorite. One objection 

 to this method of sterilisation is the rather unpleasant taste 

 which is produced in the water. This, however, is of small 

 importance so long as it does not arise from the presence of 

 free chlorine derived from the hypochlorite either directly or 

 by its interaction with traces of free mineral acids originally 

 present in the water supply. 



Free chlorine is very deleterious and ought to be avoided 

 at all costs, and it is on this account that the new sensitive 

 test for its presence (Le Roy, Compt. rend. 1916, 163, 226) is of 



