NOTES ON ATOMIC WEIGHTS. 203 



delicate piece of glass apparatus) have up to the present 

 time prevented him from carrying out his original pro- 

 gramme in its entirety. 



The paper consists of four distinct parts — 



I. The determination of the weight of a litre of oxygen. 



II. The determination of the weight of a litre of 



hydrogen. 



III. The ratio by volume in which these two gases 



combine to form water. 



IV. The synthesis of water from known weights of 



hydrogen and oxygen, the weight of the water 

 formed being also accurately determined. 



It would be impossible to give any idea of the precau- 

 tions taken to obtain results free from all objections in a 

 sketch so short as this must be, for such details the 

 original memoir must be consulted ; only a summary of 

 the results obtained can here be given. 



Three methods were adopted to determine the weight 

 of a litre of oxygen. In the first method the barometer 

 and thermometer were used, and the gases weighed in 

 balloons holding in three of the experiments about 9 litres, 

 and in the other six about 21^ litres. 



In the second method a globe of pure and dry hydrogen 

 was used as the standard for temperature and pressure, the 

 globe containing the oxygen having its pressure deter- 

 mined at the same temperature as that of the hydrogen 

 by means of a very sensitive differential manometer. 



In the third method the globes were filled with oxygen 

 when they were immersed in melting ice and the pressure 

 accurately determined at the moment of closing. This 

 method had the disadvantage of wetting the surface of the 

 globes, and probably thereby changing their weight (although 

 this was duly investigated). 



The values obtained by these three methods for the 

 weight of 1 litre of oxygen under normal conditions of 

 temperature and pressure at sea level in lat. 45 were 



By use of thermometer and manometer- = 1-42879 + "000034. 

 By compensation - 0=1-42887 + -000048. 



By use of ice and barometer - - = 1*42917 + -000048. 



