CONDUCTIVITY AND U'MIXOSITY OF FLAME8 CONTAIN! N: VAI'i'KIM.I' BALT& '."7 



Wlieii di.stilled water is sprayed the two cones of flame are blue in colour ; the 

 inner one is extremely tliin and bright. The cones are free from the reddish tints 

 (due to dust) seen in an ordinary Bunsen burner. The interconal space (dotted in 

 fig. 3) emits no light. 



When a salt solution is sprayed the characteristic radiation appears at the surface 

 of the inner cone and extends over the dotted region shown in fig. 3, forming an 

 approximately cylindrical column 3 centims. in diameter, in which the electrodes 

 are symmetrically immersed. The electrodes become bright red, the inner one lieing 

 rather brighter than the outer one is on the outside. 



After about ten minutes spraying the measurements were commenced. The 

 highest E.M.F. was usually applied first and lower ones substituted successively. 

 At the end of a series the earlier observations were repeated. 



The current was measured, and then reversed and measured again, and as the 

 current was also taken in both directions through the galvanometer, four readings 

 were obtained, and of these the average was taken. 



During an experiment one observer watched the manometers on the air and gas 

 supply, whilst the other took the galvanometer readings. 



In working with strong solutions great care is necessary to keep the air in the 

 right hygrometric state. If it is not moist enough, salt crystals dejxwit on the no/./.le 

 of the sprayer and impede the air supply ; whilst if it is too moist, drops of water 

 are deposited, with the same effect. 



In our earlier experiments with sprayers, in which the outer tube was conical at 

 the end, much trouble came from these sources ; the trouble was much less with tin- 

 form of sprayer described al>ove. 



To gauge the constancy of the apparatus we employed a i l a normal solution of 

 jx.tassium bromide. The following readings for an E.M.F. of 5'6 volts, taken at 

 intervals during three months, will give an idea of degree of constancy attained : 



21-1, 21-3, 207, 21-8, 21'6, 22'9, 22'1, 217: Mean 2T4. 



Other solutions were used, from time to time, as a control. When abnormal 

 values were obtained, an examination of the apparatus always disclosed some slight 

 remediable defect. 



Cowhictivity of the Free Flame. 



To obtain the true conducting power of a vaporised salt it is necessary, in every 

 case, to make a correction in order t-> eliminate that portion of the observed con- 

 ductivity which is due to the flame gases. For this purpose we made, in the first 

 instance, a series of observations on the conductivity of the flame, with the addition 

 only of the spray of distilled water. 



In making these experiments, it was found necessary to change the distilled water 

 at frequent intervals, otherwise the apparent conductivity steadily increased owing, it 



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