LUMINOSITY OF FLAMES CONTAINING SALT VAPOURS. 75 
Experiments on the variation of the conductivity and luminosity with the 
concentration of the salt vapour in the flame will now be described. Two similar 
and equal sprayers were used, supplying a mixture of air, gas and spray, to two equal 
burners. The sprayers were adjusted so that when both contained the same solution 
the two flames had equal conductivities and luminosities. The electrodes in the two 
flames were connected in series so that the same current passed through each flame. 
The uniform potential gradients in the flames were then inversely proportional to 
their conductivities. Fig. 5 shows one of the burners and its sprayer. Fig. 6 shows 
the two flames and the electrical connections. The luminosities were compared with 
the spectrophotometer. 
The following table contains the results obtained with solutions of sodium 
chloride :—- 
Solutions sprayed 
(grammes NaCl per litre). 
Ratio of 
conductivities. 
Ratio of 
luminosities. 
Flame A. 
Flame B. 
A/B. 
A/B. 
20 
20 
1-00 
1-00 
20 
4 
2-21 
2-14 
20 
0-8 
5-00 
4-62 
20 
0-16 
9-00 
9-75 
20 
0 
33-3 
36-7 
4 
0-8 
2-26 
2-16 
0-8 
0-16 
2-40 
2-11 
0-16 
0-032 
1-70 
2-90 
It appears that both the luminosity and conductivity are roughly proportional to 
the square root of the concentration of the sodium chloride in the flame. It was 
shown by Gouy* that the luminosity is nearly proportional to the square root of the 
concentration. 
The following results were obtained with sodium carbonate solutions :— 
Solutions sprayed 
(grammes Na 3 C0 3 per litre). 
Conductivities. 
Luminosities. 
Flame A. 
Flame B. 
A/B. 
A/B. 
18-12 
18-12 
1 
1 
18-12 
1-812 
3-1 
2-9 
18-12 
0-1812 
9-8 
8-6 
* ‘Ann. Chim. et Phys.,’ (5), 18, pp. 5-101 (1879). 
