672 itEroRT — 1884. 



When the hydrogen is less than double the oxygen, the excess of oxygen cannot 

 react with any of the three other gases present — carbonic oxide, carbonic acid and 

 steam, but has to wait until an equal volume of steam is reduced to hydrogen by 

 the carbonic oxide. The excess of inert oxygen has the same effect as the inert 

 nitrogen in favouring the formation of carbonic acid. 



The variations in the coefficient of affinity found by Horstmann with different 

 quantities of oxygen, are due partly to this cause, but chiefly to the varying 

 amounts of steam condensed by the cold eudiometer daring the reaction in different 

 experiments. 



(7) As the general result of these experiments it has been shown, that when a 

 mixture of carbonic oxide and hydrogen is exploded with insufficient oxygen for 

 complete combustion, at a temperature at which no condensation of steam can take 

 place during the reaction, and at a pressure greater than the critical pressure, an 

 equilibrium between two opposite changes is established, which is independent of 

 the quantity of oxygen taken, so long as this quantity is less than half the 

 hydrogen. Within the limits marked out above, the Law of Mass is completely 

 verified for the gaseous system composed of carbonic oxide, carbonic acid, hydro- 

 gen and steam at a high temperature. 



4. Spectroscopic Studies of Explosions. 

 By Professors Liveing, F.B.S., and Dewar, F.B.S. 1 



The explosions observed were chiefly those of hydrogen with oxygen, and of 

 carbonic oxide with oxygen, and were made in an iron tube fitted with quartz ends. 

 The spectra were both observed with the eye and photographed. Linings of thin 

 sheet metal of various kinds were introduced into the tube, and in some cases 

 metallic salts in fine powder were put in. When the tube was clean, many iron 

 lines were seen in the flash, nine lines in the green were identified, and forty-nine 

 more in the blue, violet and ultra-violet. Only one line more refrangible than was 

 observed, and that was T. Twenty-five lines of nickel and twenty-two of cobalt, 

 all lying between G and P, were photographed. No other metal gave anything 

 like so many lines as these three, but magnesium gave the b group, copper gave one 

 green and two ultra-violet lines, manganese the violet triplet; chromium, three 

 triplets in the green, indigo and ultra-violet respectively ; silver, two ultra-violet 

 lines ; sodium gave D and the pair near Q ; potassium, the violet lines and the pair 

 near 0. On the other hand, zinc, cadmium, mercury, aluminium, tin, bismuth, 

 antimony and arsenic developed no lines in the flash ; marsh gas, sulphuretted, 

 arsenetted and antimoniuretted hydrogen exploded with oxygen gave no peculiar 

 lines, merely a more continuous spectrum. It appears to be proved that iron, nickel 

 and cobalt are volatile in some degree at 3,000°, which, according to Bunsen and 

 Berthelot, appears to be about the temperature of the exploding gas ; and this may 

 help to explain the appearance of iron lines in the highest parts of solar prominences. 

 It might be possible to establish a spectroscopic scale of temperatures if the lines 

 successively developed with increasing temperatures were noted. Thus the iron line 

 T seems to be barely developed at 3,000°, the aluminium lines at H only come out 

 at a somewhat higher temperature, the lithium blue line may be just seen in the 

 inner green cone of a Bunsen burner, while the green line comes out in the 

 explosion flash. 



FRIDAY, AUGUST 29. 

 The following Papers were read : — 

 1. On the Constitution of the Elements. By Professor Dewar, F.R.S. 



1 For details, see Phil. Mag. for September 1884. 



