INORGANIC SYNTHESIS OF 'oRGANIc' COMPOUNDS 49 



like CO2, H2O, Si02, silicates, sulphates and the like which now 

 also belong to natural inorganic chemistry. 



The possible presence of these compounds is a direct result, in a 

 twofold way, of the existence of a primeval atmosphere without free 

 oxygen. First, in such an atmosphere these compounds, which at pre- 

 sent can only be formed in a natural way through the metabolism of 

 living matter, can be built by processes of inorganic chemistry. And 

 not only can they be built up regularly in such an atmosphere, but 

 they are also stable, or at least so stable that they are not destroyed at 

 a rate comparable to that of their formation. This is also due to the 

 reducing character of an atmosphere without free oxygen, in which 

 the present-day oxidizing and decomposition processes do not occur. 



But let us first look further into the reason why in such a primeval 

 atmosphere, which is anoxygenic, i.e. without free oxygen, there is a 

 possibility that simple 'organic' compounds are formed by way of 

 natural inorganic chemistry. This possibility is the direct result of the 

 absence of a shielding layer of ozone, developed from the free oxygen 

 in the higher atmosphere. Ultraviolet sunlight of shorter wavelengths 

 is then not filtered out by the ozone, and can freely reach the 

 surface of the earth. Light of such short wavelength is of very high 

 energy. One result would be, as we have seen, that present-day life 

 would be killed off by such high-energy radiation. Another result, 

 however, would be that this same high energy permits inorganic 

 photochemical reactions at the surface of the earth which do not 

 occur now, because that part of the sunlight which gets through the 

 ozone layer does not have a high enough energy. The shorter ultra- 

 violet radiation of the sun is, in fact, so rich in energy that it may 

 excite several elements of the 'thin soup' to form chemical bonds; 

 in other words, to form molecular compounds through the adsorption 

 of light quanta. This is a thoroughly inorganic process, yet under the 

 circumstances it may produce typically 'organic' molecules, up to 

 and including amino-acids. 



The process is dependent upon the absorption of light quanta from 

 the shorter ultraviolet rays: it is photosynthesis. But it is inorganic 

 photosynthesis. It must not be confused with the organic photo- 

 synthesis which takes place at present in plants through catalytic 

 action of porphyrins or chlorophyll, and mainly using light quanta 

 from the red part of the sunlight. 



