110 
Journal of the Mitchell Society [ Navember 
above mentioned. Wax tailings could be used with an easily cak- 
ing coal. 
“Pitch made from producer-gas tar is not yet on the market, 
but it will produce excellent briquets with a lower percentage of 
binder than other coal-tar pitches. It will doubtless be available 
in the future. 
“Briquets excellent in all respects except that they are not 
waterproof can be made by using 1 per cent of starch as a binder, 
the cost 'of which is 20 cents per ton of briquets produced. Extra 
care is necessary in drying and handling these briquets, and this 
adds to their cost. 
‘ ‘The waste sulphite liquor from paper mills also producees 
excellent briquets except that they are not waterproof . At present it 
is a troublesome waste product dissolved in much water. Its utili- 
zation for this purpose will bear further investigation. 
“Of inorganic binders, magnesia might be utilized, as its prob- 
able cost would not exceed 22 to 30 cents per ton of briquets pro- 
duced. Other inorganic binders, while available as regards price, 
would not make first-class briquets. 
“The briquetting of lignite coal offers a peculiarly difficult 
problem. If the lignite cakes in the fire, asphaltic residues from 
petroleum or water-gas tar pitch may be used as binder, larger 
percentages being required than for ordinary coals. The most 
promising binders for lignites that do not cake are starch, sul- 
phite liquor, and magnesia. Lignites may be briquetted without 
binder if they are to be burned on grates specially constructed to 
overcome the tendency to fall to pieces in the fire. 
“Attention is called to the suggested method of deciding as to 
the value of coal-tar pitch for briquetting purposes. The method 
is likewise applicable to asphalts and petroleum residues gener- 
ally; (1) The pitch or tar is distilled and all oils coming off 
below 270° C. are rejected as being of no value; (2) the flowing 
point of the portion to be used in briquetting is determined (this 
should generally not be less than 70° C.) (3) the pitch is 
extracted with carbon disulphide. The smaller the amount of 
residual carbon the more satisfactory is the pitch. The less read- 
ily the coal cakes the higher must be the flowing point of the 
pitch. If a pitch cracker is used, the pitch to work successfully 
