part 3.] 
Tween : Analyses of Rdniganj Coals. 
156 
Analyses of Raniganj Coals, by A. Tween, late of the Geological Survey of India. 
The analyses recorded in the following tables were made in the laboratory of the 
Geological Survey during the years 1870 to 1873. This detailed examination of Indian coals 
was undertaken by Dr. Oldham, then Superintendent of the Survey, in conjunction with 
Colonel Hyde, R. E., then Master of the Mint. A quantity of coal (about four tons) 
was sent by the leading coal companies from each of their principal pits. A large steam 
engine was set apart at the Mint, carefully fitted with instruments for recording the con¬ 
ditions of the experiments throughout, for the direct trial of these wholesale samples, each 
trial extending over several days. Portions of each coal were put aside at intervals during 
the feeding of the furnace, so as to ensure a fair average; and this was sent to the laboratory 
for analysis. Thus, as to sampling, which is so important a matter in the case of analyses, 
when so very small a proportion is actually submitted to examination, it would seem that 
every precaution was taken to ensure a safe result. 
The trials at the Mint were of so tedious a nature, not only in execution but also as 
involving a mass of complicated calculations, that there was necessarily much delay in preparing 
the results, and the publication of the analyses was postponed that all might appear together. 
As these chemical results are, however, quite intelligible by themselves, and have a value 
quite independent of the other method of trial.it seems a pity not to give them to the public. 
They are, indeed, much the more accurate and absolute results of the two, being quite free 
from the many sources of error that beset the grosser method of experiment. The one 
doubt that affects the analytical method is that of correct sampling, and, as has been said, 
every care was taken to ensure safety on this score. Some results of the practical experi¬ 
ments have been obligingly placed at our disposal by the Master of the Mint; hut unless 
accompanied by an account of the process of experiment and of calculation, the information 
would not bo complete. For a like reason we do not publish some tests of the same 
coals kindly furnished by Professor Pedler, who, at Colonel Hyde’s request, had measured 
the evaporating power by Thompson’s calorimeter. Only one small fragment (about two 
or three cubic inches) of each coal was sent, for this experiment, so the results could scarcely 
he taken as representative. 
The chemical examination was conducted in the following manner:—Several samples of 
each coal were sent, corresponding to the number of days of trial at the Mint. These were 
mixed together and broken up into small fragments, avoiding dust as much as possible. 
A portion was reserved, from which the analyses were made, and the specific gravity taken. 
The remainder was burnt in the following manner:—A small portion waB first placed upon 
an open grate and the smokeless flame of a gas burner (over wire-gauze) placed underneath. 
When this was well kindled, the larger quantity was added, and a chimney placed on top ; 
a very perfect combustion was the result, the ash, before being disturbed, retaining the shape 
of the fragments of coal, and scarcely a particle falling through the grate. 
Two hundred grains of each coal were kept at a temperature of 212° for about four 
hours for determining moisture; 50 grains were gradually heated in a closed crucible to 
bright redness for the volatile constituents and coke; 100 grains were burnt in a plati¬ 
num capsule for estimating the ash. The carbon and hydrogen in the dried coal were 
estimated by combustion with oxide of copper in oxygen gas, and the sulphur by fusing with 
nitre, carbonate of soda, and common salt. For the analysis of the ash, 50 grains of the 
larger quantity burnt were taken. This was fused in two portions with the ordinary fusing 
mixture. The acid solution of one portion, after removal of silica, was divided for the 
estimation of the sulphuric acid and phosphoric acid. The remaining constituents were 
determined from the other portion. A separate portion of each ash was examined for 
alkali by digestion with water, but no more than a trace was found in any. 
