RECENT ADVANCES IN SCIENCE 367 



of the atom, considerable attention has been devoted to the 

 problem of discovering the part played by the electron in 

 chemical affinity and in the mechanism of chemical change. 

 This problem has been investigated from several points of 

 view, with a certain, though limited, amount of success. 



One of the most promising of the different modes of in- 

 vestigation is that in which the attempt is made to determine 

 whether chemical reactions in general involve the production 

 of free charged particles, and if so, to determine the constitution 

 of such particles. It has long been recognised that many 

 reactions which occur in solution, especially when the dielectric 

 capacity of the solvent is great, involve the production of 

 charged ions which are capable of taking part in definite chemical 

 reactions. Such processes are already familiar to us in the 

 well-known phenomenon of electrolytic dissociation. This, how- 

 ever, only clears up a part of the problem. There still remains 

 the question of the production of charged particles, possibly 

 as an intermediate stage, in the case of reactions in which no 

 ionising solvent is present, reactions, in short, between pure 

 substances. 



During the past ten years numerous researches have been 

 carried out by Haber, Tanatar, Bloch, de Broglie, and others 

 upon the ionisation produced in gases when a gas reacts with 

 a solid or liquid, e.g. an alkali metal or an alloy of such metals. 

 Definite evidence of ionisation has been obtained in these cases, 

 but the interpretation of the results is much complicated by 

 the fact that such reactions are heterogeneous, and conse- 

 quently physical surface effects may be entering into the 

 phenomenon in addition to any effects brought about by the 

 chemical change itself. To obtain the simplest conditions it is 

 necessary to investigate homogeneous reactions ; in particular, 

 reactions between gases which are capable of occurring with 

 sufficient rapidity at ordinary temperatures. The first step in 

 this direction has been made by A. Pinkus (Journ. Chimie 

 physique, 16, 201 (191 8)). The problem to be settled is simply 

 this : does a chemical reaction of itself entail the production 

 of gaseous ions ? 



Pinkus has investigated the two reactions : 



2NO + 3 = 2N0 8 

 and 2NO + Cl a = 2NOCI 



