268 



MR. W. R. BOUSFIELD AND DR. T. M. LOWRY ON THE ELECTRIC \1. 



TABLE I. 



The extreme variation from the mean density for the 50-per cent, solution is only 

 0'0003, and the average error O'OOOl, some part at least of which must be attributed 

 to small errors in the measurements of density. We consider therefore that the 

 mean value, 1-5268, for the density of a 50-per cent, solution is correct within O'OOOl. 



The method adopted for measuring the density of the less concentrated solutions 

 consisted in weighing the standard solution in the pot, diluting with a calculated 

 volume of water, and again weighing to determine the exact concentration. After 

 mixing thoroughly by means of a stirrer, or one of the electrodes described in 

 Part V. of the paper, an Ostwald pyknometer of 50 cub. centims. capacity was filled 

 with the solution, and the remainder was again diluted. Although the weighings 

 were calculated to secure an accuracy of over 1 in 10,000 in the dilution, it was 

 considered desirable after 5 or 6 dilutions had been made to start again from one of 

 the standard 50-per cent, solutions, in order to avoid the influence of cumulative 

 errors such, for instance, as contamination by carbon dioxide. A typical series of 

 weighings will illustrate the method used. 



Weight of pot + 50-62 per cent, solution . 



Apparent weight of solution 

 Air 



= 1218-97 grammes. 

 = 914-95 



304-02 

 0-21 



True weight of solution 

 Weight of soda . . 



304-23 



= 154-00 



Added 35-58 cub. centims. of water. 



* The mixed solutions were stored in a glass bottle ; the remainder had not been allowed to come 

 into contact with glass. 



