and Properties of Silicmm. 261 



by bringing it into cqntact with the latter at a red heat. I 

 did not try any other process. 



If sihciuni is heated in a current of chlorine, it takes fire and 

 continues to burn. If the gas contains atmospheric air, some 

 silica remains in the form of a slight skeleton. Silicium burns 

 equally well in chlorine, whether or not it has lost its combus- 

 tibility in the air. The product condenses and presents a yel- 

 lowish liquid when it contains an excess of chlorine, but which 

 is without colour when it is freed from this excess. This li- 

 quid is very fluid; it evaporates almost instantaneously when 

 exposed to the air, yielding white vapours, and leaving a re- 

 sidumii of silica. It has a very penetrating smell, which may 

 be compared in some degree to that of cyanogen. Thrown 

 into water, it floats on the top : it generally dissolves in it, or 

 leaves a little silica. If the quantity of the water is small, a 

 drop, for example, on as much chloride of silicium, this en- 

 velops it, and the silica remains in a frothy semi-transparent 

 mass. This liquid is analogous to the combinations of the 

 other electro-negative bodies with chlorine. It reddens lit- 

 mus paper: it is the second example known of a liquid com- 

 bhiation formed by silicium. 



At common temperatures potassium has no action on chlo- 

 ride of silicium; but when heated in the vapour of the latter 

 substance it takes fire and produces a compound of potassium 

 and of silicium. The iodide of potassium does not combine 

 with silicium. 



SiUcium is neither dissolved nor attacked by the sulphuric, 

 nitric, or muriatic acids, and not even by aqua regia. In its 

 combustible state it is slowly dissolved by fluoric acid with the 

 evolution of hydrogen ; but in losing its combustibility it loses 

 also the property of dissolving in this acid. It is, on the con- 

 trary, dissolved with rapidity, even in the cold, by a mixture 

 of the nitric and fluoric acids, nitrous gas being given out. 

 Combustible silicium is dissolved by digestion in a solution of 

 caustic potasli ; but when rendered incombustible, it is no 

 longer attacked by the alkalies in the humid way. 



Silicium, when once isolated, combines with the metals with 

 much difficulty. Its remarkable affinity for platinum is known 

 by the experiments of M. Boussingault ; but it may be lieated 

 as often and as long as we choose in a platinum crucible, 

 without any combination taking place. But if we endea- 

 vour to reduce silicium by ])otassium in a platinum crucible, 

 the silicium penetrates deeply into the platinum wherever 

 this is touched by the j^otassium. Copper, silver, lead and tin, 

 heated with silicium by th<; blowpipe, do not seem changed 

 in tlicir appearance, nor in llieir ductility; notwithstanding 



when 



