16 REPOKT 1887. 



what is the amonnt of the forces at work in these chemical changes ? 

 What laws govern these forces ? Well, even in spite of the results with 

 which recent researches, especially the remarkable ones of the Danish 

 philosopher Thomsen have enriched us, we must acknowledge that we 

 are yet scarcely in sight of Maxwell's position of successful prediction. 

 Thermal chemistry, we must acknowledge, is even yet in its infancy ; it 

 is, however, an infant of sturdy growth, likely to do good work in the 

 world, and to be a credit to him who is its acknowledged father, as well 

 as to those who have so carefully tended it in its early years. 



But recent investigation in another direction bids fair even to eclipse 

 the results which have been obtained by the examination of thermal 

 phenomena. And this lies in the region of electrical chemistry. 

 Faraday's work relating to conductivity of chemical substances has been 

 already referred to, and this has been since substantiated and extended 

 to pure substances by Kohlrausch. It has been shown, for example, that 

 the resistance of absolutely pure water is almost an infinite quantity. 

 But a small quantity of an acid, such as acetic or butyric acid, greatly 

 increases the conductivity ; but more than this, it is possible by determi- 

 nation of the conductivity of a mixture of water with these two acids to 

 arrive at a conclusion as to the partition of the molecules of the water 

 between the acids. Such a partition, however, implies a change of 

 position, and therefore we are famished with a means of recognising the 

 motion of the molecules in a liquid, and of determining its amount. 

 Thus it has been found that the hindrance to molecular motion is more 

 affected by the chemical character of the liquid than by physical 

 characters such as viscosity. We have seen that chemical change is 

 always accompanied by molecular motion, and further evidence of the 

 truth of this is gained from the extraordinary chemical inactivity of pure 

 unmixed substances. Thus pure anhydrous hydrochloric acid does not 

 act upon lime, whereas the addition of even a trace of moisture sets up a 

 most active chemical change, and hundreds of other examples of a similar 

 kind might be stated. Bearing in mind that these pure anhydrous com- 

 pounds do not conduct, we are led to the conclusion that an intimate 

 relation exists between chemical activity and conductivity. And we need 

 not stop here ; for a method is indicated indeed by which it will be 

 possible to arrive at a measure of chemical affinity from determination 

 of conductivity. It has indeed been already shown that the rate of 

 change in the saponification of acetic ether is directly proportional to the 

 conductivity of the liquid employed. 



Such wide-reaching inquiries into new and fertile fields, in which we 

 seem to come into nearer touch with the molecular state of matter, and 

 within a measurable distance of accurate mathematical expression, leads 

 to confident hope that Lord Rayleigh's pregnant words at Montreal may 

 ere long be realised : ' It is from the further study of electrolysis that we 

 may expect to gain improved views as to the nature of chemical reactions, 

 and of the forces concerned in bringing them about ; and I cannot help 



