LUMINOSITY OF FLAMES CONTAINING SALT VAPOURS. 
81 
The salt vapour is not completely ionised when its concentration is extremely 
small, because of the finite number of flame ions present with which the salt ions can 
recombine. 
Part Y. —The Relative Conductivities of Salts of Different Alkali 
Metals. 
The relative conductivities of salts of different metals were determined with the 
apparatus described in Section III. The two flames were adjusted so that they had 
equal conductivities when the same solution was sprayed into them. 
It was found that when the. concentrations were large the conductivity was nearly 
proportional to the square root of the concentration with all salts. Results proving 
this to be true will be given later in this section. It follows that the ratio of the 
conductivities of any two salts, at equal concentrations, is independent of the 
concentration provided the concentration is large. 
The following table gives the results obtained :— 
Solutions sprayed 
(grammes per litre). 
Ratio of 
conductivities. 
Flame A. 
Flame B. 
B/A. 
18-12Na,C0 3 
23-6 K 2 C0 3 
9-3 
18-12Na,CO s 
25-6KC1 
9'3 
25 • 6 KC1 
20 • 2 RbCl 
0-89 
8 CsCl 
20-2 RbCl 
0-89 
The following table gives the relative conductivities, at large concentrations, of the 
salts of different metals for concentrations such that equal numbers of metal atoms 
are present in the flame in each case. The conductivity for sodium salts is taken 
equal to unity :— 
Salt. 
Relative conductivities. 
NaCl 
1 
Na 2 C0 3 
1 
KC1 
9-3 
k 2 co 3 
9-3 
RbCl 
11-8 
CsCl 
25-02 
These numbers were calculated from the relative conductivities given in the 
previous table. It was shown in Section III. that NaCl and Na 2 C0 3 have equal 
conductivities when present in chemically equivalent amounts. 
M 2 
