LUMINOSITY OF FLAMES CONTAINING SALT VAPOURS. 
73 
Solution in sprayer 
(grammes NaCl per litre). 
Ratio of conductivities 
(without CHCI 3 -r with CHC1 3 ). 
Ratio of luminosities 
(without CHCl 3 -rwith CHC1 3 ). 
0 
8-0 
1-9 
0-8 
5-7 
2-1 
4 
6-0 
1-9 
20 
6-1 
1-9 
200 
6-0 
1-9 
It appears that for all concentrations of the sodium chloride the chloroform 
diminished the conductivity about six times, and the luminosity about two times. 
It was found that the chloroform increased the current through the flame, although 
it diminished the conductivity. The current depends on the conductivity throughout 
the volume of the flame and on the resistance close to the negative electrode. The 
flame, away from the negative electrode, obeys Ohm’s law, but at the negative 
electrode there is a large fall of potential which is approximately proportional to the 
square of the current. The chloroform increased the current from four to ten times. 
Since the conductivity, measured by the ratio of the current to the potential gradient 
between the two wires, was diminished, it follows that the chloroform must have 
considerably diminished the fall of potential at the negative electrode. 
If potassium carbonate is put on the negative electrode the fall of potential there 
almost disappears, and then the current depends on the conductivity of the rest of 
the flame. It was found that with potassium carbonate on the negative electrode 
the chloroform decreased the current about six times in agreement with the change 
in the conductivity. The effect of the chloroform on the temperature of the flam? 
was measured with a thermocouple. It was found that the temperature of the couple 
was changed from about 1650° C. to 1600° C. 
If the current through the flame had been taken as a measure of its conductivity a 
large increase in the conductivity accompanied by a diminution of the luminosity 
would have been found. 
The relation between the potential difference used to send a current through a 
flame between clean platinum electrodes and the current is represented by the 
equation 
Y = Acd + Bc 2 . 
AVhere Y denotes the P.D., c the current, d the distance between the electrodes, and 
A and B are constants. The term Be 2 represents the fall of the potential at the 
negative electrode, and the term A cd the fall of potential in the uniform gradient 
between the electrodes. It appears that the chloroform diminishes B but 
increases A. 
With small potentials and currents the term A cd is relatively more important, so 
that the chloroform then should decrease the current, while with large potentials the 
term A cd becomes negligible and then the chloroform increases the current. 
L 2 
