52 PHOTOSYNTHESIS 



the necessity of investigating other forms of fuel has been very generally 



recognized. 



Probably foremost among these "synthetic fuels" is alcohol, ihis 

 has been used in limited amounts for motor fuel for many years. Owmg 

 to a complex of economic reasons the development of the industry has 

 had many difficulties to contend with. There are in general two methods 

 of alcohol formation : in the first can be included those synthetic methods 

 which start with ethylene or acetylene and in another the fermentation of 

 various vegetable materials. Regarding the first of these Monier- 

 Williams =^^ concludes: "On the general question as to whether, apart from 

 cost of production, it is sound policy to look to synthetic alcohol as one of 

 the motor fuels of the future, the following points may be considered. The 

 source of the carbon in synthetic alcohol is coal, while in fermentation 

 alcohol it is derived from atmospheric carbon dioxide. Although the 

 world's reserves of coal are ample, and there is little danger of their being 

 exhausted within a reasonable period, it is likely that the cost of raising 

 the coal will gradually increase as the more easily worked seams are 

 used up and the accessibility of the material diminishes. 



"Economy in the use of coal is a matter of national importance, and 

 it is questionable whether alcohol is the most economic form in which the 

 available carbon can be utilized as motor fuel. On the face of it, it would 

 seem preferable to work in the direction of utilizing more directly the 

 heat of combustion of acetylene, possibly by polymerizing it into hydro- 

 carbons of higher boiling-point, rather than to add to it the elements of 

 water which represent so much dead weight in the resulting fuel. Quite 

 apart from this there is the question of the electrical energy required 

 for the manufacture of calcium carbide from lime and coke. Where ample 

 water power is available, the demands made upon coal are limited to that 

 necessary for the actual formation of the carbide in the furnace. It is 

 claimed, however, that under the most favorable conditions electrical 

 power may be obtained almost as cheaply in the neighborhood of coal- 

 fields as near waterfalls. Where coal is used as a source of power, it has 

 been estimated that the amount consumed in the manufacture of synthetic 

 alcohol is nine times as great as that required for the same quantity of 

 fermentation alcohol. 



"Another point which has been raised has reference to the value as 

 a fertilizer of calcium cyanamide, prepared from calcium carbide by the 

 Frank-Caro process. One ton of carbide will yield approximately 110 

 gallons of alcohol. If the carbide is used for the production of calcium 

 cyanamide, Ca.N.CN, the nitrogen thereby made available for crops 

 amounts to 550 to 600 pounds. Applied to potato land under normal 

 weather conditions this quantity of nitrogen should result in an increase of 

 over 20 tons in the crop yield. Twenty tons of potatoes will yield at 



" Monier-Williams, C. W., Power Alcohol. Oxford Technical Publications. 

 London, 1922, p. 184. 



