238 



W. Odling, Esq, 



[March 30, 



formulae, by formulae which do not express any speculative view 

 whatever, but merely indicate the indisputable fact that these bodies, 

 or their representatives, differ from one another in composition, by 

 the successive increments of one, two, three, and four oxygen 

 atoms. 



Phosphoric acid H3PO4, is the representative on the phosphorus series, 

 of sulphuric acid H2SO4, on the sulphur series, and of perchloric acid 

 HCIO4, on the chlorine series ; but whereas perchloric 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 radicle, or the hydrogen may be partly or wholly 

 displaced by two or three different metals, or by two or three different 

 radicles, or by a mixture of metals and radicles, thus : EtKCuPOi, 

 or H(NH4)NaP04, &c. 



(^.) 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, how- 

 ever, that the substance from which it is obtained by the action of 

 chlorhydric acid, is a silicide of magnesium, represented by the for- 

 mula Mg4Si, whence the formula of siliciuretted hydrogen is assumed 

 to be H^Si, analogous to that of marsh gas H4C, a conclusion strongly 

 confirmed by the composition of chloride of silicon, which is un- 

 doubtedly Cl4Si, that is, a chloro-representative of siliciurretted 

 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 : 



Now whether or not H4Si04 is the correct formula for silicic acid, it 

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

 may be referred to that type, as illustrated in the table. 



O RTHOSILICATES. 



Et^ Si04 



Li4 Si04 



Na«H, Si04 

 Ca^ SiOs 



Mg4 Si04 



Ca,Mga Si04 

 Zn, Si04 



Silicic ether. 

 Silicate of lithium. 

 Silicate of sodium. 

 Silicate of calcium. 

 Olivine, Chrysolite. 

 Batrachite. 

 Zinc glance. 



GI4 Si04 



Ce^ Si04 



Fe^ Si04 



FcsMua Si04 



Cu^Hs Si04 



Al^Ca Si04 



AlsMn Si04 



Phenakite. 



Cerite. 



Fayelite. 



Knebelite. 



Dioptase. 



Anorthite. 



Karpholite. 



