PROPERTIES OF ELEMENTS OF SOIL. 55 



bamboo and rattan with an armor of flint, from which may 

 be struck sparks. Entering into the composition of all soil, 

 and hard and unyielding as it appears, forming not only the 

 solid rock, but the delicate flower, which that supports; 

 forming combinations with the metals of soil whose gradual 

 decomposition is the birth of fertility, silicon demands a 

 detail of its properties, commensurate with the high func- 

 tions it performs. 



68. Silicon, in the purest state yet obtained, is a dull 

 brown powder, soiling the fingers. It dissolves in fluoric 

 acid, and in caustic potash. Heated in air or oxygen gas, it 

 burns vividly, and is partly converted into silica. Heated 

 in a closed crucible, it shrinks very much, but does not 

 vaporize. Heat has altered all its properties. It has be- 

 come a deep chocolate color. It sinks in oil of vitriol, one 

 of the heaviest of fluids ; it will dissolve in no acid, except 

 a mixture of nitric and fluoric ; caustic alkali has no action 

 on it, nor will it burn in the intensest flame of air or oxygen 

 gas. No other simple substance is so changed by heat. 

 The only substance exhibiting analogous properties, is 

 carbon. 



Silicon burns in vapor of sulphur, and forms sulphuret of 

 silicon. This easily dissolves in water, sulphuretted hydro- 

 gen escapes, and silica remains in solution. These are facts 

 of the highest importance in agriculture. 



69. Whether heated or not, silicon is oxidated when heated 

 with dry potash, and converted into silicic acid. In its pure 

 state, this is a rough, gritty, tasteless powder. When 

 heated, it runs like red-hot ashes, and the lightest puff* blows 

 it away. It is not melted in the strongest heat of a wind 

 furnace. Silicic acid exists in two states, soluble or insolu- 

 ble in water. It is perfectly insoluble, after having been 

 heated red-hot. Sulphuret of silicon, as has been noticed 



