( 346 ) 



On the Graphite or Black-Lead of' Ceyhn. 



Several years ago, splendid specimens of graphite were pre- 

 sented to me by one of my pupils, who brought them from the 

 island of Ceylon, where, he informed me, the mineral occurs in 

 masses varying in magnitude from the size of a nut to several 

 inches in diameter, imbedded in gneiss. Mr J. Prinsep has 

 lately, in the " Gleanings of Science," an interesting periodical 

 published at Calcutta, published the following analysis of one of 

 the varieties : Carbon Q%S, iron 5.4, silica 21 .0, alumina 9.3, lime 

 0.2, magnesia 0.1, manganese a trace, and loss 1 .2, — 100. Sus- 

 pecting, from the large proportion of earthy impurity in this ana- 

 lysis, that some of the matrix had remained mechanically mixed 

 with the graphite, Mr Prinsep made the following additional 

 analyses : 1 . The graphite,, uncleaned, left, as above, iron and 

 earth, per cent. 37.2. 2. Roughly cleaned, left a residue per 

 cent. 18.5. 3. Crystals selected with care, 6.0. 4. Another trial 

 left the very small proportion of 1.2. The two last residua 

 did not entirely dissolve in muriatic acid ; indeed the former 

 yielded 0.3 of silica on analysis. This statement is illustrative 

 of the accuracy of Karsteh's view of the composition of gra- 

 phite, namely, that it is a mere modification of carbon, and 

 the iron and earths are accidentally mixed parts*. The gra- 

 phite of the Himala Mountains yielded to Mr Prinsep the 

 following ingredients : Carbon 71.6, iron 5.0, silica 15.0, alu- 

 mina, &c. 8.4 = 1 00.0. The English graphite was found by 

 Mr Prinsep to yield, hygrometric moisture 2.7, carbon burnt 

 off with difficulty 53.4, iron taken up by acid 7.9, earthy im- 

 purities 36.0 = 100.0. As this variety was marked of '* supe- 

 rior quality ,"*' it follows that, chemically considered, it is inferior 

 to the kinds found in Ceylon and the Himalas. 



The Ceylon graphite, Mr Prinsep informs us, has only been 

 known commercially for five or six years ; the government had 

 shipped small quantities of it to England by way of trial, and 

 it answered so well, that they were induced to receive it, amongst 

 other articles, in lieu xxf revenue, at a fixed valuation, when they 

 were suddenly surprised at the quantity of this novel currency 



• Karsten's interesting experiments on graphite will be found in one of the 

 volumes of this Journal. * 



