f78 SPONTANEOUS IGNITION OF CHARCOAL. 



Infine powder Mr. Robin, commissary of the powder mills of Essonne, 

 igmte> s^qn- j^ given an account in the Annaies de Chimie, No. 35, 

 p. 93, of the spontaneous inflammation of charcoal from the 

 black berry bearing alder, that took place the <23d of May, 

 1801, in the box of the bolter, inlo which it had been sifted. 

 This charcoal, made two days be ore, had l»een ground in 

 the mill without showing any signs of ignition. The coarse 

 powder, that remained in the bolter, experienced no altera- 

 tion. The light undulating flame, unextihguishable by 

 water, that appealed on the surface of the sifted charcoal, 

 was of the nature of inflammable gas, which is equally un- 

 extinguishable. 



Moisture pro- The moisture of the atmosphere, of which fresh made 

 saotes this. , , . , . , , . , . 



charcoal 19 very greedy, appears to me to have concurred in 



the developement of the inflammable gas, and the com'-»us-» 



tion of tne charcoal. 



In heaps heats It has been observed, that charcoal powdered and laid 



$ rong y * in large heaps heats strongly. 



and takes fire. Alder charcoal has been seen to take fire in the ware- 

 houses, in which it has been stored. 



About thirty years ago I saw the roof of one of the low 

 wings of the Mint set on fire by the spontaneous combustion 

 of a large quantity of charcoal, that had been laid in the 

 garrets. 



Fired in Mr. Malet, commissary of gunpowder at Pontailler, near 



pounding. Dijon, has seen charcoal take fire under the pestle. He 

 also found, that when pieces of saltpetre and brimstone were 

 put into the charcoal mortar, the explpsion took place be- 

 tween the fifth and sixth strokes of the pestle. The weight 

 of the pestles is 80 pounds each, half of this belonging to 

 tKe box of rounded bell metal, in which they terminate. 

 The pestles are raised only one foot, and make 45 strokes 



jp a minute. 

 Jnpredients ft* Jn consequence of the precaution now taken, to pound 

 * r u o n u po d wder m the charroa', brimstone, and saltpetre separately, no explo- 

 jatejy. sions take place ; and time is gained in the fabrication, since 



the pasu- is made in eight hours, that formerly required four 



and twenty. 

 ^Manufacture. Every wooden mortar contains twenty pounds of the 



mixture, to which two pounds of water are added gradually, 



■ Th r 



