420 [May 15, 



The theory of Professor Rogers is borne out by these analyses, but, 

 as the chemical results are exceedingly different, the proportion of 

 volatile matter being only half that cited by the American geolo- 

 gist, I think it right to append a letter which I have received 

 from Dr. Percy, in order to show the details of his manipulations, 

 and the pains bestowed by him on an analysis which, in the case 

 of anthracite, is exceedingly difficult. 



Letter from John Percy, M. D. to C. Lyell, Esq. 



Birmingham, Feb. 17.1 845. 

 My dear Sir, 



I have now much pleasure in transmitting to you, in a complete form, the 

 analyses of the specimens of coal which you sent me. The ultimate analysis of 

 coal requires considerable care, as it is difficult, by the ordinary method of com- 

 bustion with an oxidising body, to effect completely the oxidation of all the car- 

 bon. In every instance I have used chromate of lead as the oxidising body, 

 and have employed a degree of heat sufficient partially to melt the Bohemian- 

 glass combustion tube, although defended by inclosing it in thin sheet copper. 

 I have been particularly careful not only to mix, but to triturate, the coal pow- 

 der and the chromate of lead intimately together. The coal powder has been 

 dried in the oil-bath at a temperature ranging between 110° and 120° Centig. 

 The analysis of coal consists of three parts ; viz. 



1. Of the determination of the carbon and hydrogen. 



2. Of the determination of the nitrogen. 



3. Of the determination of the ash. 



The oxygen, of course, is found by deducting the sum of these from the 

 weight of coal employed in analysis. As I have already stated, the carbon and 

 hydrogen were found in the usual way by burning with chromate of lead, as in 

 an ordinary organic analysis. The nitrogen was ascertained by Will's method, 

 which consists in heating the coal with the mixture of soda-lime in a combustion 

 tube ; all the nitrogen is evolved in the form of ammonia, which is retained in 

 the receiver, containing hydrochloric acid ; the hydrochlorate of ammonia thus 

 formed is converted into ammonio-chloride of platinum, from which the quantity 

 of nitrogen is estimated. Lastly, the ash was found by incinerating in a plati- 

 num crucible until every speck of carbonaceous matter had disappeared. 



I shall now proceed to give you all the data obtained by analysis : 



1. PoMEROY Coal, Ohio. Colour of the powder, deep snuff-brown. 



\st Analysis. 

 4*878 grs. gave 



Water, 2-46 = Hydrogen, 0-273, or .5-59 per 100. 



Carbonic Acid, 13 -74 = Carbon, 3 747, or 76-81 do. 



2wd Analysis. 

 5*686 grs. gave 



Water, 2*96 = Hydrogen, 0-328, or 5 76 per 100. 



Carbonic Acid, 15 -97 = Carbon, 4-355, or 76-59 do. 



Nitrogen Analysis. 

 6-90 grs. gave 



Metallic Platinum, 0-836 = Nitrogen, 0*118, or 1-71 per 100. 



