84 
PROFESSOR W. R4MSAY AXD DR. M. W. TRAVERS 
to liquid ; and the critical phenomena are sharp. This is known not to be the case 
with a mixture. Our opinion is that this portion of the table is complete. 
We have next to show that the properties of these elements vary periodically, like 
those of the cognate elements. 
Refvactivities .—The found refractivities of the inactive gases compared with am as 
unity are ;— 
Helium. Neon. Argon. Krypton. Xenon. 
0-124 0-235 0-968 0450 2-368 
We see here a progressive increase with atomic weight. 
The following table gives a resume of the refraction-equivalents of the elements, 
taken from the summary in Ostwald’s ‘ Allgemeine Chemie,’ vol. 1, p. 447 ; the 
refractivities of the inactive mises have been calcidated to the same basis as those of 
O 
the other elements :— 
Hydrogen. 
1-47 
Helium. 
0-47 
Lithium. 
3-8 
Beryllium. 
4-0 
Boron. 
4-0 
Carbon. 
5-0 
Nitrogen. 
4-1 
Oxygen. 
3-5 
Fluorine. 
1-4 
Neon. 
0-89 
Sodium. 
4-2 
Magnesium. 
7-0 
Aluminium. 
8-4 
Silicon. 
7-5 
Phosphorus. 
18-3 
Sulphur. 
16-0 
Chlorine. 
10-0 
Argon. 
3-68 
Potassium. 
8-1 
Calcium. 
10-4 
Scandium. 
Titanium. 
25-5 
Vanadium. 
25-3 
Chromium. 
19-9 
Iron. 
12-0 
Manganese. 
12-2 
Nickel. 
10-4 
Copper. 
11-6 
Zinc. 
10-2 
Gallium. 
Germanium. 
Arsenic. 
15-4 
Selenium. 
30-5 
Cohalt. 
10-8 
Bromine. 
15-3 
Kry])ton. 
5-51 
Rulndium. 
14-0 
Strontium. 
13-6 
A'^ttrium. 
Zirconium. 
21-0 
Niobium. 
Rhodium. 
\ 
Palladium. 
. 22-4 
Silver. 
13-0 
Cadmium 
13-6 
Indium. 
Tin. 
27-0 
Antimonju 
24-5 
Tellurium. 
21-6 
Iodine. 
Xenon. 
Caesium. 
Bai’ium. 
24-5 
9-0 
19-5 
15-8 
Of these, hydrogen, chlorine, bromine, nitrogen, and oxygen, are, with the exception 
