xxx. The Fermentation of Cacao 



more favourably with petrol than is popularly 

 supposed. The fuel consumption of internal 

 combustion engines using alcohol is from 370 

 to 380 grm., or about 13 oz. to 13-5 oz. per 

 effective horse-power hour ; and when using 

 alcohol of a calorific value of 6,000 calories 

 there is obtained a thermal efficiency of some 

 22 per cent. At one time alcohol was in 

 commercial use in Berlin for automobile work, 

 but by reason of its high price, compared with 

 that of petrol, its use was discontinued ; and in 

 Paris it has been used successfully with an 

 equal proportion of benzol for motor-buses. 



" In internal combustion engines using alcohol 

 the explosive mixture can be compressed to 

 a much higher degree than can a mixture of 

 petrol vapour and air before self-ignition takes 

 place. When the alcohol is hydrated, the 

 compression can be carried still further, so that, 

 although the fuel is poorer, a larger percentage 

 of it can be converted into useful work. In 

 practice the compression is carried to 10 or 14 

 atmospheres, this high figure being made 

 possible by the water which is present in the 

 alcohol used. It is a fact that alcohol when 

 slightly adulterated with water is a better fuel 

 than when pure. 



"As to the properties of alcohol, from experi- 

 ments the heat value of alcohol appears to lie 

 between 13,310 and 11,664 B.t.u. per lb., the 

 latter value being the one most generally 

 accepted. One gallon of pure alcohol (specific 



