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Royal Institution :• 



acid contains only one atom of hydrogen, and can form only one class 

 of salts and ethers ; whereas sulphuric acid contains only two atoms 

 of hydrogen, and can form only two classes of salts and ethers ; 

 phosphoric acid contains three atoms of hydrogen, and can form 

 three classes of salts and ethers. One-third, two-thirds, or three- 

 thirds of its hydrogen may be displaced by a metal or basic radical, 

 or the hydrogen may be partly or wholly displaced by two or three dif- 

 ferent metals, or by two or three different radicals, or by a mixture of 

 metals and radicals, thus :— EtKCuPO 4 , or H (NH 4 ) NaPO 4 , &c. 



(S.) There is yet another primary hydride to be considered, 

 namely, that of silicon, the siliciuretted hydrogen of Wohler. The 

 composition of this body has not been ascertained. It has been 

 ascertained, however, that the substance from which it is obtained 

 by the action of chlorhydric acid, is a silicide of magnesium, 

 represented by the formula Mg 4 Si, whence the formula of siliciu- 

 retted hydrogen is assumed to be H 4 Si, analogous to that of marsh- 

 gas, H 4 C, a conclusion strongly confirmed by the composition of 

 chloride of silicon, which is undoubtedly CI 4 Si, that is, a chloro- 

 representative of siliciuretted hydrogen Each primary hydride, 

 hitherto considered, has yielded a remarkably stable acid, formed 

 by the addition of four atoms of oxygen to the hydride ; and hydride 

 of silicon ought to behave in the same manner, thus : — 



Chlorhydric acid .... H CI H CIO 4 Perchloric acid. 



Sulphydric acid . . . . H 2 S H 2 S O 4 Sulphuric acid. 



Phosphamine H 3 P H 3 P O 4 Phosphoric acid. 



Hydride of silicon . . H 4 Si H 4 Si0 4 Silicic acid. 

 Now whether or not H 4 SiO 4 is the correct formula for silicic acid, 

 it is certain that the great majority of simple and well-defined sili- 

 cates may be referred to that type, as. illustrated in the Table* 

 Orthosilicates. 



Et 4 Si0 4 



Li 4 SiO 4 



Na a H 2 SiO 4 



Ca 4 Si0 4 



Mg 4 SiO 4 



Ca a Mg a Si0 4 



Zn 4 SiO 4 



Gl 4 SiO 4 



Ce 4 SiO 4 



Fe 4 SiO 4 



Fe 2 Mn 2 Si0 4 



Cu 2 H 2 Si0 4 



Al 2 Ca SiO 4 



Al 2 Mn SiO 4 



Silicic ether. 

 Silicate of lithium. 

 Silicate of sodium. 

 Silicate of calcium. 

 Olivine, Chrysolite. 

 Batrachite. 

 Zinc glance. 

 The next Table illustrates the general relations of the perchloric 

 salts and ethers to their sulphuric, phosphoric, and silicic analogues. 

 The existence of the silicated compounds corresponding to the 

 formulae in italics, has not yet been established. 

 Acids, Salts, and Ethers. 

 fNaCIO 4 

 EtCIO 4 



Phenakite. 



Cerite. 



Fay elite. 



Knebelite. 



Dioptase. 



Anorthite. 



Karpholite. 



HC1 



HC10< 



