200 NEW SOUTH WALES COALS. 
Speaking generally, the coals which yield a large percentage of 
volatile hydro-carbons may be said to be the best adapted for the 
manufacture of gas. 
It will also be at once apparent that the specific gravity in 
most cases affords a very good indication of the quality of the 
coal. As a general rule, ordinary coals which possess a hi 
specific gravity contain a large proportion of as 
TABLE II. 
WESTERN District CoALs. 
Proximate Constituents. 
_ Name of Colliery. oa “bydro- et a vn Sp. gr. | Coke. 
prea 
Wallerawang .............. 1:95 | 2725 | 61:86 | 8-04 | .... | 1808 | 1 
Do. vets 151 | sa24 | 55-74 | 950 | .... | 2ose | OM 
Vale of Clwydd ............ 210 | 33:35 | 53-38 | 9:30 | 137 | 1323 | 6% 
Lithgow Valley ............ 1-95 | 3418 | 52:34 | 1012 | 1°41 | 1929 | 6246 
Bowenfells ................ 2-36 | 23°35 | 5654 | 1140 | 1-85 | 1309 | None 
Wide | 200 | 33°55 | 49-07 | 1201 | 157 | 1895 | 628 
- is noticeable that the quantity of ash yielded by these western 
coals is much greater than is yielded by the northern ones, also 
that the specific gravity is higher as a rule. 
e ash in all the specimens examined is white and _— 
whereas many of the northern coals yield ashes of a buff or 
tint, which are often quite loose and flocculent. 
It is a common opinion that the relative amounts of _ 
present in different coals can be approximately estimated by al 
redness of the ash—on the supposition that the whole of the 
phur exists in the coal in the form of iron pyrites—but such 
the case ; on referring to the analyses on the Northern ee 
coals, it will be seen that some of the coals which left pure oa 
coloured ashes contained the largest amount of sulphur & 
that others which left red ashes contained the smallest quantity 
of sulphur. in 
Sulphur may be present in coals in vari 8 
combination with iron as pyrites, which is the most io 
w. . ¢ col 
of all—as sulphuric acid in combination with ; potash ; 
stituents of the coal, such as alumina, lime, magnesia, OF 
or it may even exist in the form of organic compounds. 
