62 THE ATOMIC WEIGHTS. 



Marignac's* three results are as follows : 



8.520 grm. BaCl., gave 9.543 BaSO^. Ratio, 112.007 



8.519 " 9.544 " 112.032 



8.520 " 9.542 •• 1 1 1-995 



Mean, 1 12.01 1, dr .0071 



Rejecting Turner's single result as unimportant, we may 

 combine the other series : 



Berzelius 112. 175, =b -0034 



Struve 112.0938, rh .0018 



Marignac 112. on, ±.0071 



General mean 112. 106, ±.0015 



The data from which we are to calculate the atomic weight 

 of barium may now be tabulated as follows : 



(i.) Agj : BaCl2 : : lOO : 96.3596, zb .0009 



(2.) Ag2 : BaCl2.2H.^O : : lOO : 113. 1 13, ± .0067 



(3.) BaCl2 : 2AgCI : : lOO : 137. 841, ± .0047 



(4.) Per cent, of H2O in BaCl2.2H20, 14.799, ± .0014 



(5.) BaSO^ : BaNjOe : : 112.028, d= .014 



(6.) BaCU : BaSO^ : : loo : 1 12. 106, rh .0015 



From these ratios, with the aid of the atomic weights 

 already established, we can immediately calculate four inde- 

 pendent values for the molecular Aveight of BaCL, : 



From (i) BaClj = 207.510, i .019 



From (2) " = 207.662, dr .027 



From (3) " =z 207.536, zb .017 



From (4) " =206.837,^.045 



General mean " =r 207.505, i .011 



We have here an interesting example of the compensation 

 of constant errors. Ratios (2) and (4) both represent work 

 done by Marignac upon barium chloride containing water 

 of crystallization. If now, as is not improbable, the salt 

 contained a trifling excess of water, the molecular weight of 

 barium cliloride as calculated from .(2) would come out too 

 high, while on the other hand the result from ratio (4) 

 would err in the opposite direction. In point of fact, the 



*Journ. f. Prakt. Chem., 74, 212. 1858. 



