18G Pedler — On tlie Calcutta Coal- Gas. [August^ 



Silliman and Wurtz* that by the admixture of such gases as oxygen 

 and nitrogen with coal-gas, its illuminating power is destroyed very 

 rapidly. 



Thus in the case of air, for every one per cent, added to coal-gas, there 

 is a loss of rather more than one-half a candle power. No doubt a consider- 

 able part of the loss is due to the oxygen present in the air, but there is also ' 

 a considerable part due to the presence of the nitrogen ; I have little doubt 

 that in the case before us, there is a loss of from 3 to 4 candles in 

 the illuminating power of the gas, due to the presence of the nitro- 

 gen. I have also made some series of analyses on the gas supplied at diffe- 

 rent hours of the same night, but have found that practically it has nearly 

 the same composition at whatever time it is collected. A series of three 

 analyses of gas collected at different times on the same evening is given in, 

 the three last columns of the table. 



I have not attempted to make many determinations of the other im- 

 purities present in the gas, that is to say, the amounts of Sulphur and 

 Ammonia, as they are regularly determined by the Gas Examiner to the 

 Municipality. There is, however, no reason whatever why the Calcutta gas 

 should not be as free from these substances as any other gas-supply. As 

 already stated, the quantity of Ammonia present in the gas is enormous, 

 and it is a sign of the most imperfect purification. There is no difficulty 

 in removing the whole of this impurity, and the quantity present is at least 

 fifteen times as much as the maximum quantity that ought to be present. 

 The quantity of Sulphur on the other hand is not so large as might be 

 expected, but this arises probably not so much from the very complete puri- 

 fication of the gas, as from, the fact that Indian coals on the whole do not 

 contain a very large proportion of sulphur. I hope, however, at some future 

 time to return to these two impurities. 



To sum up the result of these experiments, it may be said that it 

 is probable, if care were taken during the manufacture of the gas to ex- 

 clude the nitrogen (which must come in from the air), and also if the car- \ 

 bonic acid present in the gas were removed, that the illuminating power of 

 the Calcutta gas instead of being only 13 candles, would be increased to 

 about 17 or 18 candles. The greater part of the carbonic acid present in 

 the gas is due to the air drawn in during the process of manufacture, the 

 oxygen of which combines with the red-hot coke or carbon forming Carbo- 

 nic acid. The quantity of air which is thus drawn in amounts to about 17 

 per cent, and is the cause of the two impurities nitrogen and carbonic 

 acid. 



*^ American Journ. Science and Arts [2] XL VIII, p. 40. 



