F. W. Mar — .Estimation of Barium as the Sulphate. 291 



The results of these determinations indicate plainly a loss of 

 barium sulphate, but inasmuch as the felts used had been 

 made very thin and it had been subsequently observed that a 

 small quantity of the sulphate could be collected in one of the 

 nitrates of the series by giving a circular motion to the water, 

 it was thought that the thinness of the felts might offer an 

 explanation of the loss and of the varying results of the series. 

 The following series was, therefore, made in exactly the same 

 manner except that care was taken to have the felts carefully 

 made and reasonably thick. 



BaCl 2 . 2H 2 taken. 



BaS0 4 found. 



Error. 



(7) 0-5014 grm. 



0-4V85 grm. 



0-0004 grm 



(8) 0-2227 " 



0-2122 " 



0-0005 " 



(9) 0-5003 " 



0-4773 " 



0-0004 " 



(10) 0-5046 " 



0-4814 " 



0-0004 " 



These results are uniform and indicate a trifling loss only ; 

 though in the nitrates of these experiments, also, a very 

 slight, but, as it proved upon refiltering ; unweighable amount 

 of the sulphate could be collected. The precipitate in the last 

 of these experiments was filtered off almost immediately after 

 precipitation, and before it had completely subsided. In an- 

 other case the whole operation, including the three weighings 

 necessary was conducted to a finish in forty-five minutes. 



In spite of the appearance of the trifling deposit in the 

 filtrate, the deficiency in barium sulphate in these determina- 

 tions was not greater than should be expected from the 

 accepted solubility of that salt in water. To ascertain the 

 effect of strongly acid solutions upon the solubility of barium 

 sulphate the following determinations were made. 



In experiment (11) the same amounts of the sulphuric and 

 hydrochloric acids, 10 cm 3 and 15 cm* respectively, were used 

 as before, but the total volume was reduced to 100 cm 3 . In 

 (12) and (13) the same total volume as before, 400 cm 3 , was 

 used, but this volume contained 150 cm 3 of the strong hydro- 

 chloric acid instead of 15 cm 3 as in the preceding experiments. 



BaCl 2 . 2H a O taken. 



BaS0 4 found. 



Error. 



(11) 05016 grm. 



(12) 0-5004 " 



(13) 0-5001 " 



0*4888 grm. 

 0-4779 " 

 0-4776 " 



0-0002 grm.— 

 0-0000 " 



o-oooo " 



It appears from these experiments that, as in the preceding 

 series, the solubility of barium sulphate in solutions constituted 

 as described is not increased by the free hydrochloric acid, and 

 that the effect upon the solubility when this acid is present in 



Am. Jour. Sci. — Third Series, Vol. XLI, No. 244. — April, 1891. 

 19 



