PRELIMINARY REPORT ON PEAT. 299
The ash, fixed carbon and volatile matter (other than water) together add up to ioo% in each case. The sulphur and nitrogen are part of the volatile matter determined separately. The percentages of ash and fixed carbon added together give the amount of coke which may be obtained from each sample, for in the process of coking enough heat is used to drive off all the other ingredients.
The fuel value is given in "British thermal units" per pound. A British thermal unit is the quantity of heat required to raise the temperature of a pound of water one degree Fahrenheit, or, to be more precise, from 50 to 510 F. If the fuel value is given as io,ooo B. T. U., for instance, this means that a pound of the material if burned under the most favorable cul'ditions could be made to raise the temperature of 5 tons of water I', or 7 t)il -1, etc.