1813.] 



Analysis of Graphite, 



299 



and indicated titanium, though still probably combined with a 

 small residue of iron. 



In this manner I found that 200 grains of this graphite, after 

 being boiled in water, and burnt with saltpetre, left a residue 

 which consisted of 



Black oxide of iron . , , II '6 grains. 



Silica 7*0 



Alumina 4*6 



Oxide of titanium 6 3 



29-5 



The graphite previously examined had exactly the appearance 

 of this last specimen. It follows from it that English graphite is 

 not quite free from copper. The two specimens differed a little 

 from each other in their specific gravity. 



That of the first was 2*250 



That of the second 2*320 



When we boll English graphite in nitro- muriatic acid, nitric 

 acid, or muriatic acid, these acids dissolve ten per cent, of the 

 constituents of graphite which are not charcoal. This separation 

 of these constituents from the charcoal in this way is rather 

 against the supposition that the charcoal is chemically combined 

 with the iron, or with any of the other constituents. The 

 charcoal of wood exhibits very different properties. Whether in 

 this last the charcoal is already oxydized, as it seems to be in 

 graphite, or whether, as Berthollet supposes, it be united to 

 hydrogen, are quite different questions. The Spanish graphite 

 frequently contains foreign bodies in distinct masses. These are 

 sometimes crystallized. When we boil it in water, we obtain a 

 solution of sulphate of iron and sulphate of copper. When the 

 graphite is burnt with saltpetre, we frequently find traces of 

 chromium in it. Besides these foreign substances, I have like- 

 wise found iron pyrites in this graphite. It is not improbable 

 that it contains likewise copper ])yrltes. The only reason for 

 suspecting the accuracy of this supposition is the small proportion 

 of copper obtained when the graphite is burnt, and the residual 

 ashes analysed. 



I boiled pounded Spanish graphite in water, in order to re- 

 move the soluble salt, and burnt 200 grains of it with ten times 

 its weight of saltpetre in a silver crucible. The combustion did 

 not take place till the heat had been continued for a considerable 

 time. But as soon as the powder was introduced, there imme- 

 diately appeared on its surface the greenish blue flame which 

 characterizes pyrites. 



The saline ley obtained by washing the residue of the combus* 



