176 VOLUMETRIC'DETERMINATION OF BARIUM AND SULPHATE. 



Heat gently to gbout 60'^C. with constant shaking, allow to stand 

 for a few moments, and then proceed as given under Volumetric 

 Barium from (A) to (Z). 



Thus, if we took A c.c. of sulphate solution, B c.c. of ^ BaCl^ 

 (factor =/g), and D c.c of ^ Kj^CrO^ (of factors f^, and f^ as 

 shown under Volumetric Barium), and we required M c.c. of 

 10 Na^SjOg (factor == F) to remove the liberated iodine, the weight 

 of SO., in 100 c.c. of the solution — 



- LTV" "^ ^M -^H 77/ 1 loooj 



gm. 



Remark. — The method gives absolute results. The BaCl^ 

 solution should be standardised against the ^^^ K^CrO^ solution, as 

 used and described under Volumetric Barium. 



If the sulphate solution contains Iron, zinc or nickel, a slight 

 excess of NagCOg (SO^ free) is added to it, the precipitated 

 carbonates, etc., filtered off, washed with hot water, the washings 

 being added to the filtrate. 



Excess of HCl is added and the CO, boiled off; then proceed 

 as given above. • 



University, 



Stellenbosch. 



