124 7?. W. Langley — Determination of Barium in Rocks. 



P. 2 0„ MnO, CI, and F were present in small amounts and were 

 not determined. Ba, Sr, S, S0 3 and C0 2 were absent. 



To determine the influence of barium upon the results, four 

 samples of this rock of one gram each were taken. To each 

 was added an amount of BaCl 2 .2H 2 equivalent to five milli- 

 grams of barium oxide. The material was fused with sodium 

 carbonate and the analyses carried on in the usual manner up 

 to and including the separation of silica. In the filtrates 

 from two of the silica precipitates, barium was separated by 

 the method previously outlined. The other two analyses were 

 conducted as usual without regard to barium. The percent- 

 age results are as follows. In column five the results obtained 

 with the original sample free from barium are given for com- 

 parison. 



Barium Barium not Barium 



removed removed absent 



Fe 2 3 + Al.,0 3 + Ti0 __. 31-68 31*39 ... 31'47 



BaO 0-53 0-56 ... 



CaO..._. 6-69 ... 6-73 6-81 6-77' 



MgO .... 3"46 3-57 3-72 3*77 3-48 



It appears that the only determination affected by this amount 

 of barium is that of magnesium oxide. The average of the 

 two determinations of magnesium oxide made without remov- 

 ing barium is 0*27 per cent higher than in the original material. 

 Assuming that barium is precipitated as phosphate [Ba 3 (P0 4 ) 2 ] 

 and weighed with the magnesium pyrophosphate in the deter- 

 mination of magnesium oxide, the product of the factor for 

 converting magnesium pyrophosphate to magnesium oxide, 

 and the weight of barium phosphate derived from five milli- 

 grams of barium oxide, equal 0*0024: grams. This accounts 

 for the fact that the magnesium oxide figure is only 0'27 per 

 cent too high when 5 milligrams of barium oxide are present. 

 The presence of barium did not affect the accuracy of the 

 determination of calcium oxide. The method for separating 

 barium gives accurate results, and introduces no errors into 

 the other determinations. The purification of barium sul- 

 phate by solution in concentrated sulphuric acid is necessary. 

 In one of the determinations the weight of barium sulphate 

 plus impurities before purification corresponded \o 0*8 per 

 cent instead of 0'5 per cent of barium oxide. 



I wish to thank Prof. H. W. Foote for his advice. 



Sheffield Chemical Laboratory, 



New Haven, Conn., May, 1908. 



