Non-luminous Radiation emitted hy a Gas Flame. 



61 



Cell IT 215-0 27-8 01672 



220 27 -8 01593 



215 -0 27 -8 -01672 



01646 



It is usually stated that water saturated with, alum is more adia- 

 thermanous than pure water. 



Melloni found (' Annales de Chimie,' vol. 153, 1833, p. 1) that 

 12 per cent, of the total radiation of an oil lamp with double air 

 current passed through 9 - 21 mm. of a solution of alum contained in a 

 glass cell, whilst 11 per cent, passed through the same thickness of 

 water, or that the diathermancy of these two liquids in glass cells was 

 practically the same. 



It seems very unlikely that no other observations should have 

 been made on this point, but a careful search has failed to disclose 

 the record of any. 



A solution of ammonia alum, saturated at about 15°, was prepared, 

 and some preliminary observations were made with it in the manner 

 already described ; the coefficient of transmission for Cell I appeared 

 to be slightly less, and that for Cell II slightly greater than when the 

 cells were filled with water, but the differences were so small that it 

 was thought that it would be more satisfactory to fill Cell I alter- 

 nately with the alum solution and with pure water, and note the 

 deflections of the galvanometer. Table IV gives a number of these 

 readings : twelve were first made with the alum solution, and then 

 twelve with water, and then twelve more with the alum, and finally 

 twelve with water. 



Table IV. 

 Deflection of Galvanometer. 



Mean. 



Cell I. 





. 3 7 



3 



8 



3 



•2 



3-7 



3 2 



3 5 







3-6 



3 



•o 



3 



•4 



37 



3 7 



3 9 







3 5 



3 



•8 



3 



•8 



3-7 



3-7 



3 6 







35 



3 



5 



3 



•3 



3-1 



3 6 



3-8 



Cell I. 





, 3 4 



3 



6 



3 



•3 



3-9 



3-6 



3-4 







3 9 



3 



•7 



3 



"5 



3-6 



37 



3 5 







39 



3 



•8 



3 



•4 



3-6 



3-7 



3 7 







3 6 



3 



7 



3 



•4 



3 2 



3 6 



37 



3 55 



3-60 



The table shows that with the form of apparatus used there is no 

 measurable difference between the absorption of an alum solution con- 

 tained in a glass cell and that of pure water. 



