, Dr F^'fe on the Prevent ion of Smoke ^ S^c, 53 



« Numerous statements have been given of the amount of 

 ^evaporation produced by the combustion of fuel in the mOi>t 

 approved furnaces. In the experiments, the results of which 

 I liave given in the published papers already alluded to, the 

 utmost from Scotch coal of good quality was Q.io lb. of water 

 from 32 for each pound of coal ; and if we suppose the eva- 

 porative power of Scotch coal to be to that of English coal as 3 

 to 4, then, in the furnace that I used, the result would have 

 been as 8.8 with a similar consumpt of fuel, which is nearly the 

 same as that obtained by others. The highest products on re- 

 cord, with which I am acc^uainted, are those of Parkes, given 

 in the Transactions of the Institution of Civil Engineers, vol. iii. 

 part 1. ; and by Henwood also in the same Transactions. In 

 one trial by Mr Parkes, in which every precaution was used 

 to prevent, as much as possible, the loss of heat, the evapora- 

 tion from Newcastle coal was 10.32 from 212, which, allow- 

 ing the degrees of heat in steam beyond 32 to be 1136, as 

 stated by Despretz, would be reduced to 8.68 from 32. In 

 my trials with Scotch coal it was Q.Q ; and keeping in view the 

 comparative strength of English and Scotch coal, the results 

 very nearly agree. In one of the trials recorded by Henwood, 

 100 lb. of Newcastle coal evaporated 16.95 cubic feet of water 

 from 94, which gives 10.54 lb. for each pound of fuel, and re- 

 ducing this to 32, the result is 9.96. 



The quantity stated in the above trials is far short of what 

 it is said coal ought to evaporate, whether we calculate this 

 from the quantity of oxygen which it requires for complete 

 combustion, or from the known composition of the coal. 



In the paper on the Heating Power of Coal-gas, published 

 in the Transactions of the Society for 1840, I have stated 

 that it required the consumpt of about 16 feet of gas to boil 

 off 1 gallon of water from 32, consequently it would requu'e 

 1.6 to boil off 1 lb., i. e. 7000 grains. Now 1 of gas requires 

 on an average about 1.8 of its bulk of oxygen for combustion, 

 supposing the gas to be about the sp. gr. 570. 1 foot of oxy- 

 gen weighs 587 grs., or nearly so, and 587 x 1.8=1057, con- 

 sequently the oxygen necessary for the consumption of 1 foot 

 of coal-gas, of the quality stated, will weigh about 1057 grs. 



