24 PYROTECHNY. • [l. 



Charcoal. — Violette has applied highly heated steam to 

 char wood, for the purpose of making a superior charcoal 

 adapted to the manufacture of common gunpowder. The wood 

 being enclosed in a cylinder, concentric within another which 

 is heated, the steam from a low-pressure boiler is highly heated 

 in a tube-coil, in the same fire which heats the cylinder, and 

 enters the outer cylinder at one end, from which it enters the 

 wood and expels the more aqueous and less combustible vo- 

 latile portions. A black or red coal is produced, according to 

 the heat and length of exposure to the steam. (Lond. Journ. 

 50. 1849, and J. Fr. Inst. (3) xvii. 281.) 



Pure Oxygen. — According to Poggendorff, Chevreul, and 

 Vogel, the oxygen made from commercial chlorate of potassa 

 always contains chlorine derived from some perchlorate in the 

 original salt. After repeated crystallizations the chlorate will 

 yield pure oxygen. (Buch. Rep. iii.) 



Preventing and extinguishing Comhustion. — To render com- 

 bustible substances incapable of combustion, at least incapable 

 of spreading fire, is evidently a desideratum, and various sub- 

 stances have been proposed at different times to effect this 

 result. In most cases they have been solutions, which are 

 applied to the surface of wood, &c., and penetrate it but a 

 short depth, or not at all. Of these, silicate of potassa (soluble 

 glass) has been most preferred. Their action is, however, 

 limited to the prevention of inflammation from sparks falling 

 on a surface thus prepared. R. A. Smith (Phil. Mag. xxxiv. 

 and Amer. Journ. 2d ser. viii. 118) proposes impregnating 

 wood, &c. with a solution of sulphate of ammonia, which, if 

 heated, is resolved into sulphurous acid, nitrogen, &c., which 

 would tend to extinguish commencing combustion. 



The following composition, among others, has been given for 

 extinguishing fires : a mixture of 1 part powdered sulphur, 1 

 part red ochre, and 6 parts copperas, added to the water of a 

 fire engine is said, from experiment, to do five times as much 

 execution in extinguishing fire as water alone ; it also di- 

 minishes the annoyance of smoke and steam. It doubtless 

 operates in a large measure from the evolution of sulphurous 



