THE ATOMIC WEIGHTS OF BORON AND FLUORINE. 27 



table 1, which gives the results in the order in which they were 

 obtained; none have been omitted. In this account, however, 

 the experiments, involving identical operations, have been 

 described collectively. 



In some instances the weight of the original "borax glass" 

 was also determined and may be found in the table. Unfortun- 

 ately, this preliminary weight was not taken in every case, for 

 the exact amount of the residual water, at first, seemed of little 

 importance, the chief object being to remove the water completely 

 and to make truly anhydrous borax the initial substance. Later 

 it was realized that very important conclusions were to be drawn 

 from the quantity of such residual water; its significance is evident 

 from table 2 and will be discussed in due time. 



FINAL DETERMINATIONS. 



EXPERIMENT IV: THE RATIOS BETWEEN SODIUM TETRABORATE, SODIUM CHLORIDE, 



AND SODIUM SULPHATE. 



The distillation of anhydrous borax with hydrochloric acid 

 and methyl alcohol had been utilized by Ramsay and Aston in 

 deriving the ratio of sodium borate to sodium chloride. The 

 results obtained by them will be discussed in Chapter III. In 

 the present case it seemed well to determine the ratio Na 2 B 4 7 : 

 2NaCl by a method strictly analogous to that leading to the ratio 

 Na 2 B 4 7 : 2NaF, for in addition to the direct ratios the relation 

 NaCl : NaF, by cross-reference, was to be used. As previously 

 indicated in Chapter I, the conversion of borax into sodium 

 fluoride was most easily effected indirectly through the formate, 

 a method which will be described more fully in the next experi- 

 ment. Hence, the conversion of borax into sodium chloride also 

 was to include the use of formic acid. 



As the general procedure in the final dehydration of borax 

 was the same in all determinations, it will be outlined before the 

 experiment proper is described. 



The empty bulb (protected from the direct flame) was strongly 

 ignited for at least 30 minutes while a current of dry air passed 

 through the apparatus. It was weighed and ignited again until 

 two consecutive weighings did not differ more than 0.02 milligram, 

 approximately. With the empty bulb such an agreement could 

 usually be obtained after two ignitions. The jacketing of the 

 3 



