262 



MR. W. R. BOUSFIELD AND DR. T. M. LOWRY ON THE ELECTRICAL 



tube and allowed to flow back into the pot. As a result ot this distillation the 

 upper part of the pot was kept free from soda and no loss was incurred when the flask 

 was removed and the lid of the pot wiped in order to weigh the solution. 



The weight of the solution was roughly determined before allowing it to cool, 

 and after adding from a burette the volume of water required to dilute to 50 per 

 cent, a careful weighing was made and the exact percentage calculated. The water 

 required for dilution was also used to rinse the wire of the cradle and the upper 

 parts of the pot. The balance used was sensitive to O'OOS gramme and the weight 

 of the sohition was about 400 grammes ; the errors of weighing and the slight errors 

 due to variations in the weight of the apparatus were less than those introduced by 

 using the accepted value for the atomic weight of sodium. 



In order to illustrate the method, a typical series of weighings may be given : 



Bomb and sodium = 269 805 grammes. 



after pouring = 119-245 



Sodium = 150-560 



Cradle and lid and sodium = 236 978 



= 86-402 



Sodium = 150-576 



Total oxidation = 0-016 gramme. 



Mean weight of sodium = 150-568 



Air correction = 0-166 



True weight - 150-734 



Weight of pot, &c., and solution = 1441-285 



924-140 



Solution = 517-145 



Air correction = 0-334 



True weight of solution = 517-48 grammes. 



Weight of sodium hydroxide = 150-734x1^ 



tO ' U5 



= 261-95 grammes. 

 Concentration of solution = 50-62 percent. 



(3.) Purity of the Material. Although the method used was calculated to give 

 solutions approaching more nearly to accuracy and purity than those prepared by 

 any other of the available methods, both the sodium and the hydroxide were tested 

 for impurities which might have vitiated the subsequent measurements. By using 

 the metal as raw material it was possible to ensure that the soda contained no acid 

 impurities such as chloride or sulphate, and as the solution was protected from the 



