12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 54 



From these figures the ratio H : becomes — 



1G.124 

 15.863 

 16.106 



Mean, 16.031, ± .057 



As the weighings were not reduced to a vacuum, this correction was 

 afterwards applied by Clark/ who showed that these syntheses really 

 make = 15.894; or, in Berzelian terms, if = 100, H = 12.583. The 

 value 15. 894, ±.057 we may therefore take as the true result of Dulong 

 and Berzelius' experiments, a figure curiously close to that reached in 

 the latest and best researches. 



In 1842 Dumas ^ published his elaborate investigation upon the com- 

 position of water. The first point was to get pure hydrogen. This gas, 

 evolved from zinc and sulphuric acid, might contain oxides of nitrogen, 

 sulphur dioxide, hydrosulphuric acid, and arsenic hydride. These im- 

 purities were removed in a series of wash bottles; the HoS by a solution 

 of lead nitrate, the HgAs by silver sulphate, and the others by caustic 

 potash. Finally, the gas was dried by passing through sulphuric acid, 

 or, in some of the experiments, over phosphorus pentoxide. The copper 

 oxide was thoroughly dried, and the bulb containing it was weighed. 

 By a current of dry hydrogen all the air was expelled from the apparatus, 

 and then, for ten or twelve hours, the oxide of copper was heated to dull 

 redness in a constant stream of the gas. The reduced copper was allowed 

 to cool in an atmosphere of hydrogen. The weighings were made with 

 the bulbs exhausted of air. The following table gives the results : 



Column A contains the symbol of the drying substance; B gives the 

 weight of the bulb and copper oxide; C, the weight of bulb and reduced 

 copper; D, the weight of the vessel used for collecting the water; E, the 

 same, plus the water; F, the weight of oxygen; G, the weight of water 

 formed; H, the crude equivalent of H when = 10,000; I, the equiva- 

 lent of H, corrected for the air contained in the sulphuric acid employed. 

 This correction is not explained, and seems to be questionable. 



A. B. G. D. E. F. G. H. I. 



H.SOi 291.985 278.806 480.807 495.634 13.179 14.827 1250.5 1249.6 



344.548 324.186 488.227 511.132 20.362 22.905 1249.0 1248.0 



316.671 296.175 439.711 462.764 20.495 23.053 1248.1 1247.2 



P,Ob 625.829 568.825 884.190 948.323 57.004 64.044 3250.6 1249.0 



H^SO* 804.546 728.182 887.331 973.291 76.364 85.960 1256.2 1254.6 



533.726 490.155 867.159 916.206 43.571 49.047 1256.3 1255.0 



661.915 627.104 839.304 878.482 34.811 39.178 1254.6 1253.3 



1 Phil. Mag. (3), 20, 341. 

 ^Compt. Rend., 14, 537. 



