from the Coal Mines, near Newcastle. 391 



With 43*5 measures of the same gas, and 22*9 of explosive mixture, the 

 loss in eight minutes was 21*7, the platinum ball being introduced warm. 



With 55 measures of the same gas, and 7 of explosive mixture, a cold 

 platinum ball caused a loss of 6 - 3 in six minutes. 



The action was equally rapid with the other gases, nearly the whole ex- 

 plosive mixture disappearing within the first or second minutes after the 

 introduction of a platinum ball, whether warm or cold. In no instance did 

 barytic water subsequently admitted, detect in the residue a trace of car- 

 bonic acid gas. 



When to any specimen of fire-damp, hydrogen was added, the action of 

 platinum always revealed the presence of air. When the quantity of air 

 was small, the action of platinum was of course slow, nor did it in 

 that case indicate with fidelity the quantity of air present, a portion of 

 oxygen not uniting with hydrogen. Thus in the fire-damp from the yard 

 coal seam Burraton Colliery, nitrous gas indicated the presence of 6"2 per 

 cent, of air, and platinum only 3"3 per cent. In the gas from the Bensham 

 Seam, Wallsend Colliery, nitrous gas indicated the presence of 9 per cent, 

 of air ; whereas platinum detected only 5 per cent, in one trial, 8*5 per 

 cent, in a second, and 6 per cent, in a third. A certain degree of impedi- 

 ment to the action of platinum by marsh gas, is thus rendered apparent. 

 But when the fire-damp was freely mixed with air, then after the hydrogen 

 gas platinum acted freely, and I have found, under such circumstances, the 

 indications from platinum to coincide with those from nitrous gas. Thus 

 in fire-damp from the low main coal seam, Killing-worth Colliery, of speci- 

 fic gravity 08226, platinum and hydrogen indicated 9"4 per cent, of oxy- 

 gen, equivalent to 46'5 of air, and in two experiments with nitrous gas 

 precisely the same result was obtained. A ball of platinum may hence be 

 applied to determine the air in fire-damp, even when its quantity is small, 

 by first diluting the gas with a known quantity of air, or enlivening the 

 action of the platinum by adding some explosive mixture. 



To those chemists who chance to be practically conversant with the 

 action of platinum on gaseous mixtures, the evidence above adduced as to 

 the freedom of fire-damp from hydrogen, carbonic oxide, olefiant gas, sul- 

 phuretted hydrogen, and similar inflammable gases, will, I doubt not, be 



