220 Profs. G. D. Liveing and .T. Dewar. [Feb. 19, 



C or G, or anywhere else, could be detected. The pressure was 

 carried up to 12 atmospheres, and at this pressure the visible 

 Spectrum was brilliant, but, in the ultra-violet, photographs showed 

 that the spectrum consisted only of what we have called the " water- 

 spectrum," very strong and sharp. The lines of this spectrum 

 showed no signs of expansion even at a pressure of 12 atmospheres, 

 and, though much more intense than at ordinary pressures, remained 

 clearly defined. 



Observations were continued .with the eye up to 25 atmospheres 

 pressure, but no trace of emission, or absorption, corresponding to 

 either spectrum of hydrogen could be detected, and it is doubtful if 

 either spectrum can 'be produced in such a flame. Since the formation 

 of steam from its component gases is attended with a diminution of 

 volume, increased pressure will increase the stability of the com- 

 pound, and the flame will contain a larger proportion of steam, as 

 well as have a higher temperature, than at ordinary pressures. 



The water formed when the flame was a jet of oxygen burning in 

 hydrogen was found to be alkaline, and to contain ammonia. But 

 the proportion of ammonia was much less than the proportion of 

 nitric acid formed when the jet was hydrogen burning in oxygen ; a 

 specimen titrated contained 0'004 per cent, of ammonia. 



Affects of (Pressure- on the Sodium Spectrum. 



In order to see what effect would be produced by incr 

 pressure on the spectrum of other substances in "the 'flame, 

 charged the hydrogen with sodium vapour by making it pass, befor 

 entering the experimental cylinder, through a mall iron cylinder, 

 - in the figure, containing metallic sodium, heated by a lamp. As the 

 D lines of sodium are very easily expanded and self-reversed in 

 flame at ordinary pressure, some- care was needed to discriminate the 

 effects which were really to be ascribed to pressure. The gas was 

 easily charged with sodium vapour, and "when burning in oxygen, not 

 only the D lines, but the citron and green pairs, and sometimes 

 blue pair (X 467), and the orange pair (X 616), were well seen ; bt 

 we could not find that they were expanded by increase of pressure. 

 A sudden change of pressure generally produced an expansion, but it 

 did not last; the lines fined down again when the pressure was 

 steady, whether that pressure was high or low. These experiments 

 were continued up to a pressure of 40 atmospheres without any 

 definite Effect on the width of the lines* which could be ascribed to 

 the pressure. 



It may be said that at the higher pressure the evaporation of the 

 sodium would be slower, and so the proportion of sodium vapour to 

 hydrogen be dimini&hed ; also, when the lines are diffuse at the 



