M. St.-Claire Deville on Alloys of Silicon. 115 



zinc, and one part of sodium, is projected into it. The reduc- 

 tion of the siheon is accompanied by a very feeble action, which 

 is not enough to produce complete fusion of the substances ; and 

 it is necessary to heat the crucible to redness, and to maintain 

 it in this state until the contents are completely fused. 



The heat must not be so high that the zinc would volatilize ; 

 the crucible is allowed to cool, and when broken is found to con- 

 tain a regulus of zinc saturated in its whole mass, but especially 

 at its upper surface, with fine long needles of silicon. To extract 

 them, it is merely necessary to dissolve the excess of zinc in hy- 

 drochloric acid. 



In this manner large crystals of silicon are obtained with ease, 

 and in greater quantity than by any other method. It is pos- 

 sible that zinc, from its many useful qualities, may become a 

 most valuable agent in the preparation of elements by metallic 

 solution. 



If the zinc-silicon be heated, the zinc is gradually volatilized, 

 but a very high temperatm'c is necessary for this. Pure silicon 

 may be melted and cast in moulds. Copper and silicon unite in 

 various proportions. A very hard, brittle, and white alloy, con- 

 taining 12 per cent, siheon, is obtained by melting together three 

 parts silico-fluoride of potassium, one part sodium, and one part 

 of copper, at such a temperature that the fused mass remains 

 covered with a very liquid scoria. The copper takes up the whole 

 of the silicon, and remains as a white substance less fusible than 

 silicon, which may serve as basis for other alloys. An alloy with 

 5 per cent, silicon has a beautiful bronze colour, and will pro- 

 bably receive important applications. 



Silicon and iron combine to form an alloy which is a sort of 

 fusible steel, in which carbon is replaced by silicon. The sili- 

 ciurets are all of them quite homogeneous, and are not capable 

 of being separated by liquation. 



A new determination of the atomic weights of cobalt and of 

 nickel has been made by R. Schneider*. The numbers hitherto 

 adopted, 29-55 for cobalt, and 29-49 for nickel, rest upon the 

 determinations of Rothoff; and Berzelius considered that the 

 small difi'erence arose from an error of observation, and that the 

 two metals have the same atomic weight. Rothoft's method con- 

 sisted in converting a weighed quantity of pure oxide into the 

 chloride by solution in liydrochloric acid, and then evaporating 

 the excess of hydrochloric acid, and determining the chlorine in 

 the pure chloride as chloride of silver. 



]}ut the method cannot be considered very reliable; for 

 although chlorine determinations are accurate, the preparation 



* Poggcndorff's Annakn, July 1857. 

 12 



