‘i COAL ECONOMY. 
It will be seen that the light oils first pass over, from which benzene can 
‘be obtained. Benzene is of wide industrial use. It is the source from which 
anilin is prepared, and it is from anilin that most of the coal tar colours are 
obtained. On fractional distillation the light oils, after treatment, yield — 
refined benzol, for use as a motor fuel, and solvent naphtha, with a certain 
amount of phenol and pyridine bases. The middle oils pass over next. They 
are rich in phenols and are of value for the manufacture of naphthalene, 
carbolic acid, and other chemicals, especially disinfectants. The creosote 
oils distil over between 230° and 270° C., and are largely used, for example, 
for treating timber, such as railway sleepers, for preservation purposes. The 
fraction distilling above 270° C. is called “ anthracene oil,’ and is the starting 
point from which the series of alizarin colours is derived. The residual 
pitch is used for various industrial purposes, e,g., in the artificial asphalt 
industry, in the manufacture of coal briquettes, &c. There is a large but 
somewhat irregular demand for it. 
The utilization of coal by methods of destructive distillation may be 
effective in three different ways, which are differentiated from one another 
by the primary products obtained. The three methods are :— 
(a) High-temperature carbonization, as carried out at gas works in 
horizontal or vertical retorts at temperatures ranging from 
1,000° to 1,300° C. 
(6) High-temperature carbonization, as carried out at coke works 
at temperatures from 1,200° to 1,300° C. 
(c) Low-temperature carbonization. 
The primary product of the first process—(a)—is a high calorific value gas, 
largely used as an illuminating gas, but now increasingly used for fuel and 
power purposes, and ordinarily known as coal gas. The residual coke, as well 
as the tar and ammonia by-products, are the secondary yields in this par- 
ticular mode of carbonization. In Australia, the ammoniacal liquors from 
_ gas works are generally saved, but the tar is not ordinarily distilled beyond 
the first stage, the main products being refined tar for road-making purposes 
and benzol. In the existing stage of the chemical industry in Australia, 16 
would not ordinarily pay to go beyond the first stage in the distillation of tar, 
as it is not economical to work up the various products except in very large 
quantities. Modern developments in the gas industry are in the direction 
of obtaining the highest possible proportion of the total thermal units in the 
coal in the form of gas for distribution to consumers. No development 
of the gas industry on the lines of the present process of carbonization is, 
therefore, likely to help very materially in the production of fuel oils. Well- 
recognised uses exist for the by-products of the gas industry, and it may fairly 
be expected that the extension of the chemical industry in Australia will 
result in the utilization of these products along natural lines of develop- 
ment. 
In the second high-temperature process—(b)—the operation is conducted 
to obtain the hard firm coke required in metallurgical processes, as for example, 
in the smelting of iron. Considerable quantities of coke oven gas are also — 
obtained, and this is used partly to provide the heat required for carbonization. 
The surplus gas can be used for much the same purposes as coal gas. 
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