258 POPULAR SCIENCE MONTHLY 



is shown by the relative heats of combustion to which reference has 

 already been made. So that, at the present time, it is about an even 

 thing between the two sources of power, weight for weight, with the 

 chances good that American ingenuity will develop an alcohol motor 

 superior to the gasoline motor. 



Alcohol engines used abroad require a preliminary warming up 

 before they will start. They are sometimes started with gasoline, and 

 sometimes 25 per cent, of gasoline is added to the alcohol to cause it 

 to ignite more readily. This may militate against alcohol as a motive 

 power at the outset, but even now there are to be found in the current 

 literature descriptions of alcohol engines which will start even without 

 this brief preliminary warming. 



Numerical data as to the consumption of alcohol per horse power 

 are abundant. On the average, in small motors, the consumption at 

 present may be taken at about one and a half pints of alcohol per 

 brake horse-power hour. Professor Lucke, of Columbia, commissioned 

 by the government, is now engaged upon a series of exhaustive tests 

 of alcohol motors, and his results will be interesting. 



Alcohol burns with a non-luminous flame. There are two general 

 methods by which it may be made to furnish light. First, by adding 

 some liquid, like ' benzine,' to it, which causes the flame to become 

 luminous, and second, to utilize the heat to heat a mantle such as the 

 ordinary Auer von Welsbach gas mantle, to incandescence. 



A mixture consisting of 65 per cent, to 85 per cent, denatured 

 alcohol and 35 per cent, to 15 per cent, of the distillate from coal tar, 

 boiling between 150° and 160° Centigrade (mainly mesitylene) is on 

 the market in Germany. It is known as e Plehn's fluid ' and burns 

 with a luminous flame. 



Before the discovery of mineral oil a mixture of ethyl alcohol and 

 a very pure turpentine which was known as camphene 7 was largely 

 used as an illuminant. It is of course possible to return to the cus- 

 toms of our grandfathers, but unfortunately the price of turpentine 

 has risen enormously in the meanwhile. 



On the whole the other method, burning alcohol with a non- 

 luminous flame to heat a mantle on the plan of the Welsbach gaslight, 

 is probably to be preferred to methods for making the flame itself 

 luminous. It may be a little discouraging to prospective patentees in 



7 Camphene is another word almost as ambiguous as ' benzine.' Camphene 

 is the correct scientific name for a definite chemical compound, a solid terpene 

 of the formula C 10 H 16 . Turpentine is a mixture of pinene,. also of the formula 

 C 10 H 16 , but a liquid, and other similar substances; purified, it contains a higher 

 per cent, of pinene, but is a mixture still, not pure pinene and certainly not 

 camphene. This appropriation of scientific names by dealers to imply a higher 

 degree of purity than actually exists in their wares is a constant source of con- 

 fusion and a real hindrance to the dissemination of accurate knowledge. 



