40 THE ATOMIC WEIGHTS OF 



carbonate distilled off unchanged and it was quite evident that 

 no reaction had taken place between this ester and the borax. 

 The method finally adopted is based on the following reaction : 



Na 2 B 4 7 +C0 2 +6H 2 ^ Na 2 C0 3 +4H 3 B0 3 



If a water solution of borax be treated with carbon dioxide an 

 equilibrium will be reached corresponding to the above relation. 

 It should be possible, therefore, to so influence this reaction as to 

 lead to a complete conversion of borax into carbonate by a con- 

 tinued removal of the boric acid; which, of course, may be done 

 by means of methyl alcohol if the amount of water present be 

 relatively small. In fact, according to L. C. Jones, 7 the reaction 

 can easily be influenced in this sense. This investigator did not 

 contemplate its application for quantitative purposes and no 

 quantitative data based thereon have been discovered. However, 

 the reaction proceeded more readily than anticipated and its 

 pronounced reversibility caused no particular difficulties. 



The mode of conducting the experiment was as follows : After 

 the complete dehydration and weighing of the borax it was 

 dissolved in a little water and evaporated to dryness in a stream 

 of carbon dioxide. The residue, which probably contained a 

 considerable portion of the sodium as carbonate, was evaporated 

 many times with small portions of methyl alcohol, exactly as 

 indicated in the other experiments, the only difference being that 

 a steady stream of carbon dioxide, instead of air, was allowed to 

 pass through the apparatus. When the green flame of the boric 

 ester could no longer be detected at the mouth of the bulb the 

 residue was dissolved in water and the distillations with small 

 portions of the alcohol were resumed. The entire cycle of oper- 

 ations was then repeated twice. A grand total of 84 grams of 

 methyl alcohol was used in the determination. Finally, after 

 long-continued drying at a moderate heat, the sodium carbonate 

 was heated to fusion in the atmosphere of carbon dioxide which 

 was gradually replaced by dry air as the substance cooled. This 

 method of fusing sodium carbonate in carbon dioxide had been 

 successfully applied by others 8 and was also found satisfactory in 



7 Am. Jour. Sci., V, 442. 



8 Sackur, Ber. 43, 449 (1910); and T. W. Richards and C. R. Hoover, J. Am. Chem. 



Soc., 37, 95 (1915). 



