492 Scientific Intelligence. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



] . On the Composition of Water. — Lord Rayleigh has com- 

 municated to the Royal Society the results of an attempt at an 

 entirely independent determination of the relative weights of oxy- 

 gen and hydrogen, by actual combustion of weighed quantities 

 of the two gases. Dumas weighed only the oxygen and the 

 water produced. Later investigators have weighed the hydro- 

 gen, either in the gaseous state as in the experiments of Cooke 

 and the author, or occluded in palladium as in those of Keiser. 

 As to the second weighing it is not material whether it relates to 

 the water, as in the investigations of Cooke and Keiser; or to the 

 oxygen as in the present experiments. In principle the method 

 adopted by Rayleigh is very simple. Globes of the same size as 

 those employed for the density determinations were filled to 

 atmospheric pressure with the two gases and were then carefully 

 weighed. By means of Sprengel pumps, the gases were ex- 

 hausted into a mixing chamber, sealed below with mercury, where 

 they were fired by electric sparks in the usual way. After suffi- 

 cient quantities of the gases had been withdrawn, the taps of the 

 globes were turned, the leading tubes and mixing chamber were 

 cleared of all remaining gas,, and, after a final explosion in the 

 eudiometer, the nature and amount of the residual gas were de- 

 termined. The quantities taken from the globes can be found 

 from the weights before and after the operations. From the 

 quantity of that gas which proved to be in excess, the calculated 

 weight of the residue was subtracted. This gave the weight of 

 the two gases which actually took part in the combustion. In 

 practice, the mixing chamber, originally filled with mercury, was 

 charged with equivalent quantities of the two gases ; the oxygen 

 being first admitted until the level of the mercury had dropped 

 to a certain mark and then the hydrogen down to a second mark. 

 The mixed gases might then be drawn off into the eudiometer 

 and the chamber refilled ; but to save time the chamber was re- 

 plenished and the eudiometer filled from it simultaneously, the 

 proper proportion of the gases being preserved by means of mer- 

 cury manometers which indicate the pressures at any time in the 

 globes. To obviate an accumulation of residual gas in the eudio- 

 meter, two sparking places were provided, one above the other, 

 the lower one being generally used. When the tube contained 

 excess of oxygen down to a point somewhat below the lower 

 spark-wires each bubble of explosive gas readily found its way to 

 the sparks and there was no tendency to a dangerous accumula- 

 tion of mixed gas before an explosion took place. In consequence 

 of the difficulties encountered, five results only have been obtained, 

 representing the atomic ratio of oxygen and hydrogen as deduced 

 immediately from the weighings with allowance for the unburned 



