B.— CHEMISTRY. 49 



There is a striking analogy here with anisole and the other phenolic 

 ethers and their nitro derivatives in solution in concentrated sulphuric 

 acid which were referred to above. There can be no doubt that the ether 

 molecules in the acid solution have gained their critical quanta of activa- 

 tion, and yet their activated states must be stabilised in some way, since 

 no measurable sulphonation takes place at ordinary temperatures. When 

 the solution is warmed at 50° the expected reaction proceeds. This 

 stability of the activated states has placed great difficulty in the way of 

 explaining many observations of absorption spectra. 



Now it is very probable that there is one factor which is common to 

 the two sets of observations, namely the existence of a complex, that is 

 to say an adsorption complex of carbonic acid and nickel carbonate in 

 the one and an addition complex or solvate of the ether and sulphuric 

 acid in the other. If the mechanisin of complex formation be considered 

 it would appear that two methods are possible whereby a complex can 

 be stabilised. The most usual case is when two components form a 

 complex with a loss of energy, and such a complex will only be resolved 

 into its components by the supply of energy equal to that lost in its 

 formation. As an example of this type of complex the salt of an organic 

 base such as aniline may be instanced, this type having a positive heat of 

 formation. 



On the other hand it may be suggested that another possibility exists, 

 namely the formation of an addition complex of two components, one of 

 which yields a definite amount of energy to the other. Such an energy 

 transference, so far as external evidence is concerned, will be an isothermal 

 process. It may further be suggested that the amount of energy given 

 up by the first component to the second component is equal to the critical 

 quantum of activation of the second component. Such complexes will 

 not be formed between any two molecules, but only between two which 

 satisfy the conditions, the criterion being that a molecule of one compound, 

 possibly by loss of rotational energy, can give to the molecule of another 

 compound, energy equal to the critical quantum of activation of that 

 molecule. A complex of this type may be denoted by the symbol A~B*, 

 where B has gained its critical quantum of activation at the expense of 

 the rotational energy of A. 



Let it be accepted that such complex formation is possible in order 

 that the properties of these entities and their probable influence on the 

 phenomena under discussion may be critically examined. It may first 

 be concluded that, even though the molecule B has become activated, 

 the reaction characteristic of the activated state will not take place until 

 the energy defect of the molecule A has been restored. In other words 

 the activated state of the molecule B has become stabilised. In the 

 second place the resolution of the complex into a normal molecule of A 

 and an activated molecule of B will be secured by making good the defect 

 in the rotational energy of the molecule A. The formation of a free 

 molecule of B in the activated state is no longer a process of direct activa- 

 tion by radiant energy, which has proved to be impossible, but an increase 

 in the rotational energy which, as is known, can be efiected by means of 

 infra-red radiation. 



This hypothesis may in the first instance be applied to the phenolic 



192S E 



