Chemical Examination of the Fire-Damp. 207 



tion of water corresponding to the quantity of explosive mixture so 

 introduced, without the production of any carbonic acid. But if 

 carbonic oxide or olefiant gas were present, then cold spongy pla- 

 tinum would not act at all, a small proportion of explosive mixture 

 being employed ; and if the action were forced by using hot 

 spongy platinum, or by the free introduction of explosive mixture, 

 then would carbonic acid as well as water be generated. 



To apply these facts to the case in point, some very active pla- 

 tinum balls, of the size of peas, were made from a mixture of pipe- 

 clay, spongy platinum and the yellow ammoniacal chloride of 

 platinum, the materials being mixed with water so as to form a 

 plastic mass, which after receiving the required size and form, 

 was gently dried, and ignited for an instant before the blow-pipe,* 

 and were introduced into the gaseous mixture over mercury, 

 sometimes cold and at others warm, ten or twenty seconds after 

 incandescence. Their action on all the samples of fire-damp was 

 precisely of the same character with fire-damp, oxygen being pre- 

 viously added or not ; the platinum balls, whether cold or warm, 

 were completely inactive. On adding some explosive mixture 

 to the fire-damp, the platinum balls acted readily to their full ex- 

 tent. To give some instances : 



I. With fire-dam,p from theyardcoo.l seam Burraton Colliery^ 

 the specific gravity of which was 0-600. 



With 46-5 measures of this gas, and 12"5 of explosive mixture, 

 a platinum ball, nearly cold, caused in ten minutes a loss of vol- 

 ume equal to 12 measure. 



In a second trial the loss in ten minutes was 13-6 in a mixture 

 of 49 measures of fire-damp, and 14-1 of explosive mixture, 



II. With fire-damp from the Benshatn coal seam, Wallsend 

 Colliery, the specific gravity of which was 0-6024. 



In a mixture made with 34-3 measures of fire-damp, and 13-1 

 of explosive mixture, a platinum ball introduced warm, caused in 

 six minutes a loss of volume equal to 12-4 measures. 



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. 



* Before use the little balls were always ignited. 



