and on Alcoholic Engines. 4 1 



It is not a little remarkable, that several respectable writers, 

 whilst treating on the force of vapours, have been careful to 

 point out the great ceconomy of fuel which would attend the sub- 

 stitution of alcoholic vapour for steam as a first mover of ma- 

 chinery; and their only obstacle or objection to its universal 

 adoption is its high price, though even that they suppose might 

 in certain situations be more than compensated by the saving 

 of costly fuel*. Their chief reason for giving such a decided 

 preference to alcoholic vapour is, no doubt, its low tempera- 

 ture and small latent heat compared to those of steam having 

 the same tension ; and from which they allege an equal force 

 could be produced in the cylinder of an engine with a much 

 less expense of heat. But with every deference to such au- 

 thorities, I cannot help thinking that the supposed ceconomy 

 of fuel from the causes just mentioned, is fully counterbalanced 

 by other circumstances : so that upon the whole, an equal force 

 of* steam can really be produced with as little heat as the other, 

 and probably even less, if Dr. Ure's experiments, from which 

 I shall now calculate, be correct. 



Let us compare the quantities of heat which would be ex- 

 pended in heating water and alcohol from 45° Fahr. to their 

 respective boiling points of 212° and 175°, and in vaporizing 

 them so as to produce elastic forces equal to that of the atmo- 

 sphere, in two equal cylinders of engines. 



According to Dr. Ure, 200 grains of such steam being con- 

 densed in 32,340 grains of water, raised its temperature 6°'5, 

 or from 42° to 49°*5 Fahr. Hence '^f§f? X 6'5 = 1051°"05 

 is the range through which 32,340 grains of steam would have 

 heated the water, supposing the rate uniform : but to this we 

 should add 4° # 5 for heating the 200 grains from 45°, the tem- 

 perature of the air, to 49°'5; and we have 1055°*55 for the 

 heat spent in elevating the temperature of the water from 45° 

 to 212°, and in converting it into vapour: exclusive of a com- 

 pensation to be noticed presently. 



Again, the condensation of 200 grains of alcoholic vapour 

 raised the temperature of 32,340 grains of water 3°, or from 

 42° to 45°; wherefore, &f$3^ x 3 = 485°*1 is the rise of -tem- 

 perature which alcoholic vapour would have produced on its 



* I am not certain whether we owe this ingenious delusion to the distin- 

 guished Spanish engineer, M. Betancourt. But it has been favourably no- 

 ticed by our own countrymen, and Dr. Ure in particular has eulogized it in 

 the most glowing terms, without seeming to have been in the least aware 

 that it ran directly in the face of those very experiments of his own, from 

 which he was attempting to calculate its oeconomical qualities. — Phil. 

 Trans, for 1 818. Phil. Mag. vol. liii. 



Vol. 68. No. 339. July 1826. F weight 



