i 885 •] Recent Developments of Chemical Science. 17 
gallium, indium, thallium, lead, antimony, sulphur, sele- 
nium, and tellurium. 
Frequently : Arsenic, bismuth, tin. 
Never : Gold (occurs only in the free state), sodium, mag- 
nesium, aluminium, silicon, phosphorus. (See h.) 
As oxides : — 
Commonly : Sodium, magnesium, aluminium, silicon, 
phosphorus (see h), and tin. 
Frequently : Zinc and copper. 
Rarely : Lead, antimony, bismuth, and arsenic. 
Group VIII. — The elements of this group, with the ex- 
ception of iron, cobalt, and nickel, never occur in combina- 
tion. Hence we need consider merely these three bodies. 
Iron occurs mostly as oxide, but still also frequently as 
sulphide. Cobalt is met with mostly as sulphide, but often 
also as oxide. Nickel occurs chiefly as sulphide and arsenide, 
and but very rarely as oxide. 
Iron, the first member of this group, approaches closely 
to the elements of the even series, whilst nickel, the last 
member, approximates much to those of the odd series. 
This is a proof that group VIII. affords a gradual transition 
from the even to the odd series. 
The halogens, chlorine, bromine, iodine, and fluorine — the 
most eledtro-negative elements — occur in Nature in com- 
bination with the most eledtro-positive metals, as chlorides, 
bromides, iodides, and fluorides, and (if we disregard a few 
metallic oxychlorides and sulpho-chlorides) never in combi- 
nation with oxygen or sulphur. 
The above-mentioned fadts may thus be summarised with 
reference to Lothar Meyer’s elemental curve : — 
Elements whose position is on descending parts of the 
curve are reduced with difficulty, and never occur in Nature 
in the free state or in combination as sulphides, but always 
in union with oxygen as oxides or double oxides (silicates, 
sulphates, carbonates, &c.) ; whilst the elements which have 
their position on ascending points of the curve are easily 
reduced, and occur almost invariably to a greater or less 
extent in a free condition, or in combination with sulphur, 
and very seldom with oxygen. 
Another investigation by Prof. Carnelley likewise deserves 
notice here, as it connedts itself with the periodic law, and 
thus, indiredtly at least, strengthens the evidence in favour 
of the compound nature of our supposed elements. 
The more immediate objedt of the author’s researches is 
VOL. vii. (third series). c 
