174 THE ATOMIC WEIGHTS. 



.0146 



Rimbach * based his determination of the atomic weight of boron upon 

 the fact that boric acid is neutral to methyl orange, and that therefore 

 it is possible to titrate a solution of borax directly with hydrochloric 

 acid. His borax was prepared from carefully purified boric acid and 

 sodium carbonate, and his hydrochloric acid was standardized b}^ a series 

 of precipitations and weighings as silver chloride. It contained 1.84983 

 per cent, of actual HCl. The borax, dissolved in water, was titrated by 

 means of a weight-burette. I give the weights found in the first and 

 second columns of the following table, and in the third column, calcu- 

 lated by myself, the HCl proportional to 100 parts of crystallized borax. 

 Rimbach himself computes the percentage of Na.^0 and thence the atomic 

 weight of boron, but the ratio Na^B^O^.lOHjO : 2HC1 is the ratio actually 

 determined. 



Mean, 19.0893, =b .0006 



Obviously, this error should be increased by the probable errors in- 

 volved in standardizing the acid, but they are too small to be worth 

 considering. 



The following ratios are now avaikible for boron : 



(i) Percentage of water in NajB^O,. loHjO, 47.1756, =b .0066 



(2) 3Ag : BBr3 : : 100 : 77.425, zh .0017 



(3) Na^B^T : aNaCl : : 100 : 57.933, i .0074 



(4) 2AgCl : Na.^B^, : : loo : 70.546, zt .0146 



(5) Na2B40,.ioH20 : 2HCI : : 100 : 19.0893, ± .0006 



*Berichte Deutsch. Chem. Gesell., 26, 164. 1893. 



