The sample is heated in an aluminium retort to a temperatur of 520 °C. The products of decomposition pass into a water-cooled receiver; the tar and water are condensed while gaseous products pass to atmosphere. The coke residue and the receiver and its contents are weighed. The mass of tar is obtained by difference to the mass of water determined by entrainment with toluene or xylene. A separate determination of moisture in the coal, also by entrainment with tulene or xylen, is amde so that the decomposition water can be calculated. The peecentage of gas is obtained by subtracting from 100 the sum of the percentages of coke residue, of tar and decomposition water.