A NEW CONSTITUENT OF THE ATMOSPHERE. 237 
approximate mean between the atomic weights of chlorine and potassium) to be the 
atomie weight of the lighter element, and 40 the mean atomic weight found, and 
supposing that the second element has an atomic weight between those of bromine, 
80, and rubidium, 85:5, viz., 82, the mixture should consist of 93°3 per cent. of the 
lighter, and 6°7 per cent. of the heavier element. But it appears improbable that 
such a high percentage as 6°7 of a heavier element should have escaped detection 
during liquefaction. 
If the atomic weight of the lighter element were 38, instead of 37, however, the 
proportion of heavier element would be considerably reduced. Still, it is difficult te 
account for its not having been detected, if present. 
If it be supposed that argon belongs to the eighth group, then its properties would 
fit fairly well with what might be anticipated. For the series, which contains 
Sy Pu and Mi Ane and (Ole to walk 
might be expected to end with an element of monatomic molecules, of no valency, we., 
incapable of forming a compound, or if forming one, being an octad ; and it would 
form a possible transition to potassium, with its monovalence, on the other hand, 
Such conceptions are, however, of a speculative nature; yet they may be perhaps 
excused, if they in any way lead to experiments which tend to throw more light on 
the anomalies of this curious element. 
In conclusion, it need excite no astonishment that argon is so indifferent to reagents. 
For mercury, although a monatomic element, forms compounds which are by no means 
stable at a high temperature in the gaséous state ; and attempts to produce compounds 
of argon may be likened to attempts to cause combination between mercury gas at 
800° and other elements. As for the physical condition of argon, that of a gas, we 
possess no knowledge why carbon, with its low atomic weight, should be a solid, while 
nitrogen is a gas, except in so far as we ascribe molecular complexity to the former 
and comparative molecular simplicity to the latter. Argon, with its comparatively 
low density and its molecular simplicity, might well be expected to rank among the 
gases. And its inertness, which has suggested its name, sufticiently explains why it 
has not previously been discovered as a constituent of compound bodies. 
We would suggest for this element, assuming provisionally that it is not a mixture, 
the symbol A. 
We have to record our thanks to Messrs. Gorpon, KrLuas, and MatrHews, and 
especially to Mr. Percy WiuuiAms, for their assistance in the prosecution of this 
research. 
ADDENDUM (by Professor W. Ramsay). 
March 20, 1895. 
Further determinations of the density of argon prepared by means of magnesium 
have been made. In each case the argon was circulated over magnesium for at least 
