82 
PROF. H. A. WILSON ON THE ELECTRICAL CONDUCTIVITY AND 
The following table gives the relative concentrations (proportional to metal atoms 
per unit volume) for which the conductivities are equal. These numbers are also 
only correct for large concentrations. The concentration is taken as unity in the 
case of caesium :—- 
Metal. 
Atomic weight. 
Concentration. 
Na 
23 
626-0 
K 
39 
7-25 
Rb 
85 
4-48 
Cs 
133 
1-00 
The equation 10 4 /r = - (b + ac), which was found to represent the results 
c 
obtained with caesium chloride, can be applied to the other salts also. 
The constant a is proportional to the large concentrations in grammes per litre 
which give equal conductivities. The constant b has the same value for all salts 
when the concentrations are taken proportional to the number of metal atoms in unit 
volume. • When the concentrations are expressed in grammes per litre b is propor¬ 
tional to the molecular weight of the salt actually present in the flame. Since 
chlorides and carbonates give equal conductivities it is probable that chemically 
equivalent amounts give equal numbers of salt molecules in the flame. Probably 
the carbonates and chlorides are decomposed into oxides. The constant b for 
alkaline carbonates is therefore probably proportional to one-half their molecular 
weights. 
The following table gives the values of a and b calculated in this way so as to give 
k in grammes per litre in the solution sprayed into the flame :— 
Salt. 
a. 
b. 
NaCl 
217-00 
3-47 
NaoCO s 
197-00 
3-14 
KC1 
3-20 
4-42 
KoC0 3 
3-0 
4-10 
RbCl 
3-20 
7-20 
CsCl 
1-00 
10-00 
The following is an example of the method used for calculating the above constants. 
For RbCl we have 
121 
168-5 
a — lx 4 ‘48 x 
= 3-2. 
