278 EARTHS. 



(b.) Not attacked by water, or sulphuric, nitric, or nitro-muriatic 

 acid. Infusible, and unalterable by the blow pipe, and apparently 

 one of the most infusible of bodies. 



(c.) Fluoric acid, with a little nitric, attacks it vigorously. 



(d.) After ignition, chlorate of potash does not affect it at any 

 temperature. Nitre acts upon it violently at a white heat. If a frag- 

 ment of carbonate of soda be introduced into the mixture, it detonates. 



(e.) Vapor of sulphur unites with the ignited silicium, and becomes 

 incandescent. 



(/.) The resulting sulphuret decomposes water rapidly, and evolves 

 sulphuretted hydrogen ; silica is generated, and the water dissolves 

 it, and becomes gelatinous, but after it is dry, it remains a cracked 

 mass, and is entirely insoluble in acids. It is observed that this solu- 

 bility of silica just formed, may explain the existence of siliceous 

 crystals in closed cavities, which could never have contained water 

 enough for the solution of the materials, unless they were originally 

 in a much more soluble state. 



(g.) Silicium burns in chlorine at a red heat, and forms a yel- 

 low volatile liquid, smelling like cyanogen, and depositing silica on 

 the addition of water. 



(h.) Detonates when heated with carbonate of potash, and with 

 the hydrates of fixed alkalies, and of baryta, producing at a tempe- 

 rature below redness, vivid incandescence ; it acts upon the alkali 

 of nitre, after the acid is destroyed by heat. 



(i.) JL non-conductor of electricity. 



j.) Alloys of silicium are obtained by heating silica along with 

 other metals, but silicium once extricated from oxygen, does not form 

 alloys. 



(k.) It stains, and sticks strongly, even when dry, to the glass 

 vessels in which it is kept. 



(1.) When silicium is heated in vapor of potassium it takes Jire, 

 producing a compound of silicium and potassium. 



Remarks. It is not easy to class silicium. It can scarcely be 

 called a metal, as it is infusible, is a non-conductor of electricity, 

 and has none of the physical properties of a metal. It may be re- 

 garded as a combustible, since it burns in chlorine, and those who 

 choose to consider its combination with sulphur and potassium, with 

 emission of heat and light, as a combustion, will of course add those 

 instances as proofs of its combustibility. On the whole, it is perhaps 

 more allied to boron and carbon, than to the metals ; but carbon has 

 two metallic properties ; it is a conductor of electricity, and in the 

 form of- plumbago, and of fused charcoal, it has the metallic lustre. 

 Some of the metals, as uranium, titanium, and columbium, are rather 



* See Aim. de Chem. et de Phys. Vol. XXVII, p. 337, and Ure's Diet. p. 719, 



