Physical Relations of Osmium. ~ 299 
‘stannic and (the rutile form of) titanic acid. The bichloride of 
tin and potassium, too, is reported as crystallizing in regular 
octahedrons, like the corresponding salts of iridium, platinum, 
and palladium. 
The arsenic section, as given by Dana, includes nitrogen, 
phosphorus, arsenic, antimony, bismuth, osmium, and tellurium. 
The last-named is marked as doubtful, and should decidedly be 
-placed with sulphur and selenium, to which it is analogous in 
by far the greater number of its compounds. 
In one of the interesting memoirs lately published by Dumas, 
on the numerical relations subsisting among the atomic weights 
of the elements, the arsenic series is thus given :— 
Atomic weights. 
Nitrogen epegneg. 
Phosphorus. . . . 14417=81 
Arsenic . . . . .« 144174+44=75 
Antimony . .. . 144+17+4+88=119 
Bismuth. . . . .. 144174+176=207 
and the parallelism of this series with that of chlorine, iodine, 
&c., is supposed to be shown in the following lines :— 
F (19) Cl (35:5) Br (80) I (127) 
N (14) P (31) As (75) Sb (122) 
in which a common difference of 5 is assumed between the two 
members in each of the vertical columns (a difference not strictly 
brought out in the case of phosphorus and chlorine), and in 
which a higher atomic weight is assigned to antimony than in 
the preceding Table. Osmium is not included; but in a supple- 
mental note since published, we find it placed, with an equivalent 
somewhat higher than that usually adopted, in the sulphur group, 
serving to complete the following two lines of equivalents :— 
Mg (12:25) Ca (20) Sr (43°75) Ba (68:5) Pb (103°5) 
O (8) S (16) Se(89°'75) Te (645) Os (99°5) 
between the paired members of which a common difference of 4 
is supposed to exist. 
Let osmium and ruthenium be brought into the arsenic group, 
and the series of atomic weights will then stand thus :— 
Atomic weights. 
Nitrogen . .. . 14 
Phosphorus . . . 144+17=31 
Ruthenium. . . 14417422=53 
Arsenic . . . . 14417444=75 
Osmium . . . . 144+17+466=97 
Antimony, . . . 144+17+4+88=119 
Bismuth . . 2... 144+17+4+176=207 
