130 



Dr. A. Scott. 



[Mar. 23, 



March 23, 1893. 



Sir JOHN EVANS, K.C.B., D.C.L., LL.D., Vice-President and 

 Treasurer, in the Chair. 



A List of the Presents received was laid on the table, and thanks 

 ordered for them. 



The following Papers were read : — 



I. " On the Composition of Water by Volume." By ALEXANDER 

 Scott, M.A., D.Sc, Jacksonian Demonstrator in the Uni- 

 versity of Cambridge. Communicated by Lord Ratleigh, 

 Sec. R.S. Received March 4, 1893. 



(Abstract.) 



In a preliminary note presented to the Society in June, 1887, the 

 results of twenty-one experiments on the composition of water by 

 volume were given in detail. The ratio deduced from these experi- 

 ments was less than two volumes to one of oxygen. This result was 

 unexpected, because of the greater compressibility of oxygen than of 

 hydrogen, but as every one of the experiments pointed to this result, 

 the evidence for it seemed conclusive. Pursuing the investigation 

 with improved apparatus, especially as regarded making a complete 

 analysis of the residual gas, a serious source of error was discovered 

 in the use of any combustible lubricant for the taps employed. On 

 substituting syrupy phosphoric acid for the vaseline previously em- 

 ployed, the oxides of carbon disappeared as ordinary impurities. In 

 the later experiments two forms of apparatus were employed, the 

 chief difference being that in the earlier form the measuring vessel 

 was not of fixed volume, so that both volume and pressure of the 

 gas had to be measured ; in the later form the gas was measured at 

 constant volume by varying the pressure, which alone, therefore, re- 

 quired measurement in each experiment. 



As in the apparatus formerly used, the entire apparatus could be 

 completely exhausted of air before beginning an experiment by using 

 the mercury reservoir (Mi) and the measuring vessel as a Toppler's 

 pump. The gases were measured in A and JB, and after measurement 

 were mixed in the jar H, whence they were drawn into the explosion 

 tube J, and then exploded in fractions till all was used up. The residue 

 was now passed back into H, and then into B, and there measured, 



