Chemical Apparatus. 115 



X 



leaves no excrementitious matter. The flame of 

 oils emits soot, but this is somewhat remedied 

 by having small wicks, and increasing their num- 

 ber, or still better by the lamps with glass chim- 

 neys of Argand's invention, which have great 

 power. Oils scorch the wick and change its tex- 

 ture, so that it does not suck up the whole of the 

 oil: incombustible flax, or asbestos, &c. have been 

 used, and answer the purpose better than cotton. 

 Oils also of themselves leave a fixed carbona- 

 ceous matter which rlogs the wick. Some oils, 

 however, are more completely inflammable than 

 others, as spermaceti is better than train oil. 



2. Peat or JTutf produces a gentle heat; when 

 crude the smoke diminishes the heat, and spoils 

 the vessels ; when it has been red-hot the smoke 

 is expelled, and a kind of charcoal remains. 



3. Charcoal of wood. This is the chief fuel of 

 chemists abroad : it kindles quickly, has few va- 

 pours, produces few ashes, and they have scarcely 

 any disposition to melt so as to clog the vessels. 

 If the ashes do melt, it is only in the smallest quan- 

 tity. It is capable also of producing the intensest 

 heat; it is however soon consumed, and must be 

 quickly renewed. Though the charcoal seems 

 free from fumes, yet there is an evaporation of 

 humidity till it becomes red-hot*. 



* The smoke from common fuel is a> <l iiijt-r >ns as the 

 fume-. <>f ch;irci).,| ; but as it is dirviiMuUhnl hy Ix-ing dis- 

 agree. iLle, we iixoid it before u produces any ill rffccis. 



