50 SECTIONAL ADDRESSES. 



ethers, all the relevant facts of which have already been stated. The 

 quantitative relation between the absorption bands of these substances 

 leaves little or no doubt that each ether in concentrated sulphuric acid 

 solution has in some way gained its critical increment of activation, and 

 in spite of that fact the ether does not undergo sulphonation at ordinary 

 temperatures. It has always been very difficult to understand why this 

 activated state is a stable one and why the reaction characteristic of that 

 state does not take place unless the solution is warmed. The explanation 

 is simple enough on the present hypothesis. The entity present in 

 sulphuric acid solution is a complex or solvate of the ether and sulphuric 

 acid, in which the ether molecules have gained their critical quanta 

 of activation at the expense of the rotational energy of the sulphuric acid 

 molecules. The reaction to give the sulphonic acid and water cannot 

 take place within that complex, since the photochemical experiments 

 prove that the reaction takes place between the activated molecules of 

 the ether and free sulphuric acid molecules. The complex molecule, 

 therefore, will be stable below a certain temperature. On raising the 

 temperature the defect in the rotational energy of the sulphuric acid 

 molecules will be made good and the sulphonation will then take place. 



The hypothesis also offers an explanation of the temperature coefficient 

 of the photosjTithesis of carbohydrates from carbonic acid, referred to 

 above. In this case the complex is the adsorption complex of carbonic 

 acid and nickel carbonate, in which the carbonic acid molecule has gained, 

 at the expense of the rotational energy of the nickel carbonate molecule, 

 its critical quantum of activation to the intermediate level. So long as 

 the complex exists the carbonic acid will not undergo reaction when it is 

 irradiated by white light, and in consequence no measurable reaction 

 takes place at the lower temperatures, even though the carbonic acid 

 molecule may be raised by the absorption of light to its higher energy 

 level. When the temperature is raised the energy defect of the nickel 

 carbonate is made good and the activated carbonic acid molecules are 

 set free. Two alternatives exist as regards the final activation of the 

 partially activated carbonic acid molecules by their absorbing light. 

 Either the partially activated molecule gains its second increment of 

 activation by absorption of the photochemical quantum when it exists 

 in the complex, in which case the increase in temperature will set free 

 the fully activated molecule, or the second increment of activation is 

 gained by the absorption of the photochemical quantum at the instant 

 the partially activated molecule is set free by the rise in temperature. 

 In either case the fully activated molecules react to give activated 

 formaldehyde and oxygen, this being mmediately followed by the 

 polymerisation of the activated formaldehyde to give the hexoses. The 

 evidence is strongly in favour of the first alternative, as will presently be 

 explained. 



It must be emphasised that the temperature is a most important 

 factor, and there must be for every complex a characteristic temperature 

 limit, below which it is completely stable. In the case of the phenolic 

 ether complexes with sulphuric acid it happens that this temperature 

 lies above 15°, since the sulphuric acid solutions of the ethers undergo no 

 measurable change when allowed to remain at that temperature for 



