CHEMICAL SCIENCE. 285 



almost, if not quite as hard as the diamond itself. Crystallized boron resists 

 the action of oxygen even on strong heating, but at the temperature at 

 which diamond burns, boron oxydizcs superficially. Chlorine acts power- 

 fully on boron, which takes fire at a red heat in an atmosphere of the gas and 

 burns to gaseous chlorid of boron. No acid acts upon boron, but acid sulph- 

 ate of potash at a red heat reduces it, sulphurous acid being evolved. Hydrate 

 and carbonate of soda oxydize it slowly at a red heat but saltpetre has no 

 action at this temperature. 



The graphitoid boron is best obtained by heating fluoborate of po- 

 tassium with aluminum. Small masses of boron-aluminum arc obtained, 

 which on solution in muriatic acid leave the boron in small plates, often 

 hexagonal and having the form and lustre of native graphite and graphitoid 

 silicon. The plates arc always opaque. Amorphous boron is best prepared 

 by heating a small piece of aluminum Avith a large quantity of boric acid, 

 purifying tl:e product as above. It is a light chocolate-brown substance, pos- 

 sessing all the properties described by Bcrzelius, Gay Lussac and Thenard. 

 The authors conclude that boron resembles carbon more closely than silicon. 



OX SILICIUM AXD THE METALLIC SILICIURETS. 



Deviile and Caron have presented to the French Academy a memoir upon 

 silicium or silicon which exhibits many points of special interest. The 

 authors find, in the first place, that aluminum is not the only metal which 

 possesses the property of dissolving silicon, but that zinc may also be made 

 to act advantageously as a solvent. The preparation of crystalline silicon 

 by means of zinc is very simple and easy of execution. An earthen crucible 

 is to be heated to redness and a carefully made mixture of three parts of 

 fluosilicatc of potassium, one part of sodium cut in small pieces, and one 

 part of granulated zinc is to be thrown into it. The reaction ensuing is very 

 feeble and not sufficient to effect the fusion of the mass. The crucible must 

 therefore be kept at a red heat until the scoria is completely fused. The 

 heat must not be high enough to vaporize the zinc, or the operation would be 

 lost. After slow cooling, the crucible is to be broken, when a button of zinc 

 will be found, penetrated through its whole mass, and especially on its upper 

 surface, by long needles of silicon. These are groups of regular octahedrons 

 imbedded in each other parallel to the axis which unites the summits of two 

 opposite angles. To extract these crystals, it is only necessary to dissolve 

 the zinc in chlorhydric acid, and then boil the silicon with nitric acid. In 

 this way crystallized silicon may be obtained in more beautiful crystals, and 

 in larger quantity, than by any other method. The only portion of silicon 

 lost in this process, is that disengaged in the form of siliciuret of hydrogen 

 at the moment of the solution of the zinc. If the alloy of zinc and silicon be 

 heated beyond the point at which the metal volatilizes, the silicon remains in 

 the state of a fused mass which is entirely free from zinc. Pure silicon may 

 be fused and run into moulds. In this manner the authors prepared ingots 

 which were presented to the Academy. The authors arc now engaged in 

 studying the alloys of silicon which appear to be of much interest. The 



