30 THE ATOMIC WEIGHTS OF 



gave no test for boric acid with turmeric paper. A second portion 

 of sodium formate (containing approximately 0.02 per cent, of 

 boric acid) did respond to this test. After two evaporations with 

 methyl alcohol, however, the turmeric test gave a negative result. 

 As formic acid seemed to interfere with the turmeric reaction, 

 the residues were changed to sodium chloride by evaporation 

 with hydrochloric acid before testing for boric acid. Slight traces 

 of the latter were probably lost in this way; if so, the value of the 

 test was not greatly affected thereby. 



To return to the description of the main experiment. Before 

 the final evaporation with the alcohol the outside of the bulb 

 was rinsed with a little methyl alcohol and water to remove 

 possible traces of boric acid resulting from a slight decomposition 

 of the methyl ester. The residual sodium formate, which un- 

 doubtedly was free from boric acid, was dissolved in a small 

 quantity of water mixed with an excess of pure hydrochloric 

 acid and evaporated to dryness. The formate was thus completely 

 transposed to the chloride. In order to make doubly sure, how- 

 ever, the sodium chloride obtained was gradually heated to about 

 200 and, when cool, again moistened with a few drops of hydro- 

 chloric acid and evaporated. It was then dried very slowly in a 

 current of air and finally fused. During the actual fusion the 

 air current was all but stopped and gradually increased again 

 during the slow cooling. The salt was then weighed. A second 

 fusion, conducted as the first, produced no appreciable change in 

 weight. 



The hydrochloric acid used in this transposition was obtained 

 by allowing pure concentrated sulphuric acid to drop into strong 

 hydrochloric acid (method of Hare) free from arsenic and other 

 appreciable impurities. The hydrogen chloride gas thus released 

 was washed with concentrated hydrochloric acid and allowed to 

 fill a closed vessel containing a quartz dish with pure water. A 

 solution of hydrogen chloride was thus obtained by direct contact 

 of its components, without the use of a delivery tube. The 

 apparatus was constructed entirely of glass and the quartz dish 

 had previously been subjected to a prolonged action of hydro- 

 chloric acid. 



After the sodium chloride had come to constant weight it 

 was evaporated with a moderate excess of pure sulphuric acid. 



