M. D e ville on the various forms of Silicon. 26 9 



Then the problem becomes, to find the locus of the vertex of a 

 triangle two of whose vertices move on V, two of whose sides 

 touch U, and the third aU + /3V. Proceeding as in the com- 

 mencement of this paper, we get an equation of the eighth 

 degree, which, however, contains as extraneous factors V, and 

 the square of 



A2/32U + «/3F + A«2V, 



and the equation of the locus i-emains 



a^Y^U + «7/32F + AA'/?*V = 0. 



Trinity College, Dublin, 

 March 18, 185/. 



XLI. Chemical Notices from Foreign Journals. 



By E. Atkinson, Ph.D. 



[Continued from p. 189.] 



DE VILLE* has completed a very important investigation on 

 silicon, and has made out some remai'kable analogies between 

 this element and carbon. Like carbon, silicon has three forms : 

 (1) the ordinary or amorphous silicon corresponding to ordinary 

 charcoal; (2) graphitoidal silicon corresponding to graphite; 

 and (3) octahedral silicon, or the diamond of silicon. 



The amorphous form of silicon which was discovered by Ber- 

 zelius was described by him as being infusible, but Despretz has 

 recently succeeded in fusing it by employing the galvanic cur- 

 rent. Its fusing-poiut appears to be intermediate between that 

 of steel and that of iron. It may also be obtained fused by 

 exposure in a lime crucible to the heat produced by Deville's 



furnace t. 



The best method of obtaining this silicon pure is by the action 

 of chloride of silicon on sodium. This is effected by heating 

 sodium in a large glass tube, and passing over it the vapour of 

 chloride of silicon. An action takes place, the chloride of silicon 

 being absorbed by the sodium with the evolution of light and 

 heat. A mixture of common salt and silicon is thus obtained, 

 from which, by treatment with water, the former is dissolved out 

 and the silicon left behind. Obtained in this way, it has all the 

 appearance of the silicon described by Bcrzelius. 



This form of silicon may also be obtained pure and melted by 

 placing the sodium in porcelain trays free from iron, and heating 

 as before. After the action is over, the trays are broken, the 

 parts unacted upon are rejected, and the fragments of the trays 



* Comptes Rendus, January 14, 185G. Annales de Chimie et de Physique, 

 January 1857. 



t I'liil. Mag. February 1857. 



