As oxides or 



198 Prof. T. Carnelley on the Periodic Law, 



§ 10. (3) OCCURRENCE OF THE ELEMENTS IN THE COMBINED 



State in Nature. — In reference to what is said under this 

 section, F, 01, Br, I, and the elements of Group VIII. must 

 be neglected, as they will be considered further on, §§ 11, 12. 



Elements belonging to odd series usually occur in nature as 

 sulphides or double sulphides* ', i. e. in combination with a nega- 

 tive element belonging to an odd series, and only in very few 

 cases as oxides ; whereas elements belonging to even series, on 

 the other hand, usually occur as oxides or double oxides (form- 

 ing silicates, carbonates, sulphates, aluminates, 8fc.\ i. e. in 

 combination with a negative element belonging to an even series, 

 and never (with two exceptions) as sulphides. 



Thus :— 



Elements belonging to Even series : — 



Commonly. Li (lithia mica, &c.) K (nitre, 

 felspar, &c), Eb, Cs, Be, Ca, 

 Sr, Ba, B, Sc, Y, La, Yb, C, Ti, 



douMeTxTdes i Zr > Ce > Th > V > Nb > Di > Ta > °> 



double oxides. | Cr, Tb, W, Mn. 



Frequently. N (in nitre), Mo. 

 {^Rarely or never. None. 



The only two of these elements occurring as sulphides are : — 



Commonly. Mo. 



Very rarely. Mn (also 0, as S0 2 in volcanic 

 gases). 



Elements belonging to Odd series : — 



Commonly. Cu, Ag, Zn, Cd, Hg, Gra, In, Tl, 

 As sulphides Pb, Sb, S, Se, Te. 



(selenides, tel- J Frequently. As, Bi, Sn. 

 lurides). ] Never. Au (occurs only in free state in 



nature); Na, Mg, Al, Si, P (for 

 these see § 5). 



f Commonly. Na, Mg, Al, Si, P (for these see 



As oxides J § 5), and Sn. 



* | Frequently. Taxi, Cu. 

 [ Rarely. ' Pb, Sb, Bi, As. 



§ 11. Group VIII. — The elements of this group, except Fe, 

 Co, and Ni, never occur in nature in the combined state, and 

 therefore need not be considered in this connexion. As regards 

 the first triad of the group, 



* Also as selenides, tellurides, and arsenides. 



{ 



