Preface XXXI. 
gravity 0°79 at 59° F.) has a corresponding heat 
value of 77,274 B.t.u. One pound of 100 per 
cent. alcohol requires theoretically 9 lb. of air, 
or 111°5 cubic feet,at 62° F., for complete com- 
bustion. Care must be taken to see that the 
right quantity of air is given, because if the 
engine is run on an over-rich mixture acetic 
acid is produced and causes corrosion of the 
engine parts. 
‘A series of tests have been carried out in 
the United States with a view to determining 
whether the petrol engines now in use could be 
run on alcohol, and what improvements could 
be effected in the design to render them more 
suitable. In the trials eight engines ranging 
from 2 to 40 h.p. were’used, three of them 
being high-speed motor-car engines of which 
two were of 4o h.p., the other engines being 
of the internal combustion types such as are 
used in commercial and agricultural operations. 
Each of the eight engines was run on alcohol 
as well as on paraffin and petrol, as many as 
thirty distinct and separate tests being taken 
on some of the engines. The alcohol used 
was virtually the same as that obtainable in 
this country under the name of methylated 
spirit, and consisted of 90 per cent. of ethyl 
alcohol and 10 per cent. of methyl alcohols 
with about o’5 per cent. benzine added, the 
percentages being in volume. Its _ specific 
gravity was about 0°83. The petrol used had 
a specific gravity of -o'71, which is to say that 
