26 PHOTOSYNTHESIS 



such as cost of equipment and limitations of distribution, shows very 

 clearly that all the water powers of the country cannot suffice. 



Much attention has been given to the production of liquid fuel other 

 than petroleum. Thus far the investigations along these lines have almost 

 universally led to the opinion that the substance best suited to these 

 methods is alcohol. This is on the basis that alcohol can be produced from 

 vegetable material and is the most direct route from solar energy. It is 

 thus proposed to develop a photosynthetic industry on the basis of agri- 

 culture, the products of which are to be converted into alcohol by means 

 of fermentation. 



It is characteristic of most discussions of energy that they finally 

 revert to a consideration of our primal source of energy, the sun. It is 

 equally significant that when we arrive at this stage we realize that the 

 green plant still remains the only large scale converter of solar energy 

 through the process termed photosynthesis. 



In the process of photosynthesis nature has worked out a method of 

 utilizing solar energy. In principle this method is probably the most 

 effective imaginable. It is the only chemical reaction we know, induced 

 by visible light, in which there is a great accumulation of energy. The 

 products are easily stored, transported and capable of transformation in 

 numberless ways. As we shall see, the natural process of photosynthesis 

 is not very efficient ; but it can serve as a most valuable guide to the de- 

 velopment of a method of the utilization of solar energy. The chemist 

 need not be timid about competing with nature. He has many cases to 

 his credit in which he has learned to surpass nature both in efficiency and 

 reliability. 



3. The Green Plant as a Converter of Solar Energy 



Photosynthesis is a complex process; for its successful operation a 

 number of elements or factors are essential. These include light, carbon 

 dioxide, water, oxygen, the minute corpuscles called chloroplasts which 

 contain the chlorophyll, and a temperature at which the plant is able to 

 exist. It must also be realized that the process of photosynthesis is inti- 

 mately connected with the life processes of the plant. It is not merely 

 a manufacturing of food which makes possible the life activities of the 

 organism, but the operation of the photosynthetic process is apparently 

 as much dei>endent upon the interplay of enzymatic reactions and the struc- 

 ture of the organism as is respiration. When we consider the difficulties 

 which have been encountered in unravelling the chemistry of the respira- 

 tory process, as for instance the oxidation in the organism of glucose to 

 carbon dioxide and water, it is not surprising that the synthetic reaction, 

 starting with the relatively inert carbon dioxide and involving photo- 

 chemical reactions about which until very recently we knew practically 

 nothing, should appear as such a difficult task. 



Of all the factors which are essential to photosynthesis, light has prob- 



