BARIUM. 123 



Turner * found that 100 parts of chloride ignited with sulphuric acid 

 gave 112.19 parts of sulphate. By the common method of precipitation 

 and filtration a lower figure was obtained, because of the slight solubility 

 of the sulphate. This point bears directly upon man}' other atomic 

 weight determinations. 



Berzelius,t treating barium chloride with suli)huric acid, obtained 

 the following results in BaSO^ for 100 parts of BaCl, : 



112. 17 



112. 18 



Mean, 1 12.175 



Struve, X in two experiments, found : 



112. 0912 

 1 12.0964 



Mean, 112.0938 



Marignac's§ three results are as follows : 



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



8.519 " 9.544 " " 112.032 



8.520 " 9.542 " " III. 995 



Mean, 112. on, zb .0071 



Richards, in his work on this ratio, regards the results as of slight 

 value, because of the occlusion of the chloride by the sul})hate. This 

 source of error he was never able to avoid entirely. Another error in 

 the opposite direction is found in the retention of sulphuric acid by the 

 precipitated sulphate. Eight experiments were made in two series, one 

 set by adding sulphuric acid to a strong solution of barium chloride in a 

 platinum crucible, the other by precipitation in the usual way. Rich- 

 ards gives in his published paper only the end results and the mean of 

 his determinations ; the details cited below I owe to his personal kind- 

 ness. The weights are reduced to vacuum standards : 



( 1.78934 

 I 2.07670 



17- * I 1.58311 



First. ' -^ ■-' 



I 3.27563 

 I 3-02489 



13.87091 



( 3.02489 

 Second. •, ,, 



(3.87091 



Mean, 112.077, zb .0017 



* Phil. Trans., 1S29, 291. 



t Poggend. Annalen, 8. 177. 



t Ann. Cheni. Pharin., 80, 204. 1851. , 



g Joiirn. filr Prakt. Chem., 74, 212. 1858. 



