88 Dr Colquhoun o?i the Argillaceous Ore of Iron. 



In order to determine both the proportionate amount, and 

 also the composition of the earthy ingredient of the coals used 

 in Scotland by the iron manufacturer, several specimens were 

 taken both of the splint, and of the cherry coal. It was easy 

 to discover the first of these points ; but the incineration of the 

 coal proved to be a work of so much tediousness, that it was 

 necessary to conduct the analyses upon very small quantities 

 only, and the results, therefore, so far as regards the quantita- 

 tive proportions of the ash, are stated not without some diffi- 

 dence as to their minute accuracy. 



A very perfect specimen of splint coal, on being incinerated, 

 left 4.28 per cent, of a pure white-coloured earthy residue. 

 One hundred parts of this residue, on being analyzed, proved 

 to be composed of the following parts : 



Silica - - , - 75 



Alumina - - 12 



Peroxide of iron - - 4 



Lime - . , 2 



Sulphate of lime - - 7 



100 



When calcined in a strong red heat, in a covered platinum 

 crucible, which, again, was inclosed within a second, in order 

 to exclude as much as possible the atmospheric air, this coal 

 afforded 52.76 per cent, of coke. 



Upon incinerating a specimen of a different splint coal, which 

 was not quite so perfect in its characters as the last mentioned, 

 there was left 3.82 per cent, of ashes of a pure white colour. 

 The constituents of these ashes bore the following relative pro- 

 portion to each other : 



Silica - - - 58 



Alumina - - 32 



Magnesia . - - 2 



Lime - - - 1 



Oxide of iron - - Trace 



Sulphate of lime - - 7 



100 



