Gas-coke,
which is the residue from the gas retorts, is somewhat inferior in heating value to coke made in ovens but it is an excellent fuel where furnaces are adapted to its use. Gas-coke is often stored, by piling it in heaps, in the open and on account of its porous nature it absorbs considerable moisture. Where exposed to the weather the amount of contained moisture depends on the amount of rain or snow the coke has absorbed. This amount is easily determined by weighing a fair sample and driving off the moisture in an oven. The sample should be weighed several times until the weight remains constant.