Preface xxix. 



to separate benzol or benzine from the alcohol 

 to obtain pure or dutiable spirit. In just the 

 same way it is quite impossible to separate 

 wood spirit or methyl alcohol from the pure 

 spirit by redistilling, as, although the wood 

 spirit boils at a lower temperature, they both 

 distil over together. In England it is the 

 custom to add one-third of i per cent, of mineral 

 naphtha to the alcohol as a further precaution. 

 It would seem, therefore, that a use could be 

 found for as much benzol as could be produced 

 in denaturing alcohol and rendering it more 

 suitable for fuel. The supply of benzol would 

 be at least sufficient to cope with the demand 

 for the mixed fuel, and it could not be affected 

 in a price war, because the cheapness of 

 alcohol would be the determining factor, and 

 not the price of the comparatively small per- 

 centage of benzol. A mixture of pure 100 per 

 cent, alcohol with 9-12 per cent, of 90 per cent, 

 benzol gives the best results in practice. 



" The calorific value of alcohol is little more 

 than half the calorific value of petrol by weight, 

 but taking volumes into consideration the 

 difference is not so marked, because alcohol is 

 the heavier fuel. As will be mentioned later, 

 experiments have been made which have shown 

 that the thermal efficiency of a petrol engine is 

 not so high as that of one specially designed 

 for using alcohol, and that the net value per 

 unit of volume is not far from the same with 

 both fuels. Alcohol, in fact, compares much 



