B.— CHEMISTRY. 51 



some weeks or even months. The ether may be quantitatively recovered 

 when the solution is poured on to crushed ice. In the case of the adsorp- 

 tion complex of nickel carbonate and carbonic acid the characteristic 

 temperature limit lies at 1-2°, as shown by the dotted extension of the 

 straight line in fig. 3. 



When the temperature is progressively raised above the characteristic 

 limit an increasing number of complexes will be resolved in unit time, 

 and the reaction velocity will increase. It may be said, therefore, that 

 the stability of the complexes progressively decreases as the temperature 

 is raised above the temperature limit, and it follows that there must be 

 an upper temperature limit above which the complex will have no 

 measurable stability, and at this temperature the reaction velocity of a 

 simple chemical reaction will reach a maximum and will indeed be 

 instantaneous, if such a word can be applied to a process involving the 

 mixing together of the reactants. The photosynthesis reaction is 

 differentiated by the fact that it consists of two stages, and the tempera- 

 ture limits concern only the stability of the adsorption complex character- 

 istic of the first stage. 



The hypothesis of complex formation also offers an explanation of 

 the phenomena of photoluminescence. There is one outstanding fact in 

 connection with the activation of the phosphorogen in a phosphore which 

 indicates the presence of a complex of the type we are deabng with. In 

 all cases where the activating wave-lengths have been measured, these 

 are longer than those which are characteristic of the phosphorogen in the 

 free state. This at once leads to the view that each phosphorogen molecule 

 has formed a complex with a molecule of the diluent, and within that 

 complex the phosphorogen exists at a level of higher energy content than 

 the normal. The stability of the complex will be determined by the 

 temperature as it can only be resolved into its components by the supply 

 of infra-red radiation to make good the defect in the rotational energy of 

 the diluent molecule. Even though the phosphorogen component is 

 raised to a still higher level by absorption of its characteristic quantum 

 at the ultra-violet frequency, the complex will remain in its stable state 

 provided that the temperature is below the lower limit characteristic of 

 the complex. An instance of an exactly analogous phenomenon is the 

 very striking fluorescence of benzaldehyde in concentrated sulphuric acid 

 solution. In this case the aldehyde within the complex absorbs and 

 radiates energy without its stability being affected. It may therefore be 

 suggested that even after the phosphorogen has been raised to a higher 

 level of activation than that which it reaches in the actual formation of 

 the complex, the new state is no less stable than the complex itself. If 

 that be so the whole of the phenomena of photoluminescence which have 

 been previously described will find a simple explanation. There will be 

 a lower temperature limit below which the activated complex will be 

 completely stable, that is to say no phosphorescence will be observed. 

 When the temperature is raised above the lower limit the region of partial 

 stability will be entered and phosphorescent emission will begin, and 

 progressive rise of temperature will progressively increase the number 

 of complexes that are resolved and the intensity of the phosphorescence 

 will increase. Since there are present a finite number of complexes the 



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