432 Dr. Clarke's Analysis of a bituminous Limestone. 



1. One hundred grains being placed upon red hot iron for 

 the expulsion of the water of absorption, were thereby diminished 

 ■h of a grain. 



2. The remainder being reduced to powder in a porcelain 

 mortar and exposed to diluted muriatic acid until all effervescence 

 ceased, there remained an insoluble residue of the original dark 

 colour of the limestone, which when carefully washed and dried, 

 weighed 10 grains; allowing therefore for the weight of the 

 carbonic acid and lime, after the expulsion of the water of absorp- 

 tion, S9I grains. 



3. The supernatant acid used in this experiment being decanted, 

 and neutralized by the addition of an alkali, yielded no precipitate 

 of iron to the tincture of galls ; but the prussiate of potass threw 

 down a blue precipitate upon which however no reliance can be 

 placed ; as it is well known that the prussiate of potass is not a 

 satisfactory test of the presence of iron when this metal exists in an 

 inconsiderable portion. 



4. The ten grains of dark brown powder mentioned in No. 2, 

 being collected, washed and dried, were exposed to the heat of a 

 flame of a candle urged by the common blow-pipe, when com- 

 bustion instantly ensued, accompanied by a lambent flame, which 

 continued during some seconds, the powder thereby losing its 

 colour and becoming white ; attended also by a loss of weight, 

 amounting to 1 of a grain. Hence it is manifest that the colour 

 is owing to bitumen. 



5. To ascertain the proportion of alumine v which from its 

 chemical combination with silex remained insoluble in the muriatic 

 acid) a plan recommended by Mr. Holme was adopted. One 

 hundred other grains of the same limestone were calcined in a 

 platinum crucible, and the loss of weight owing to the expulsion 

 of the carbonic acid was found to equal 40 ,'„ grains. 



