222 Peters — Estimation of Calcium, Strontium and 



which is not diminished by the presence of a large amount of 

 ammonium oxalate, but when the dilution is increased to 

 250 cm3 , as is the case in the experiments given in section B, so 

 that the conditions correspond more nearly to those recorded 

 in sections A and B, the errors fall to a minimum. In the 

 experiments recorded in section E, in which the dilution is 

 increased to 500 cm3 , an error is introduced which is not pre- 

 vented by the presence of a large excess of ammonium oxalate 

 and which is independent of the amount of strontium salt 

 used. Eight of the water filtrates and wash waters obtained 

 in the experiments recorded in Table YI were tested for 

 traces of strontium by the addition of alcohol, and in all cases 

 a small amount of strontium was found, amounting in the 

 average to 0*0010 grin, in 100 cm3 of water. 



Barium Oxalate. 



Barium oxalate according to Souchay and Lenssen* is soluble 

 in 2,590 parts of cold water, and according to Bergmanf is 

 scarcely at all soluble in alcohol. The attempt was made to 

 estimate barium by precipitation with ammonium oxalate in a 

 mixture containing alcohol. It was found that in filtrates 

 from oxalate precipitations in which 0*l-0'2 grm. of barium 

 oxide, taken as the nitrate, had been precipitated in volumes of 

 100 cm3 containing 30 cm3 of absolute alcohol, and allowed to 

 stand over night, treatment with sulphuric acid gave barium 

 sulphate amounting in the average to no more than 0*0001 grm. 

 of barium oxide. The insolubility of barium oxalate under 

 these conditions, -therefore, is practically complete. 



The process for the estimation of barium was as follows : 

 Ammonium oxalate was added to a solution of a barium salt, 

 containing 30 per cent of its volume of alcohol, the mixture 

 was allowed to stand over night, filtered on asbestos, the pre- 

 cipitate was washed by decantation with 100-200 cm3 of water 

 containing 30 per cent of its volume of alcohol, and dried 

 over a flame to insure the removal of alcohol. The crucible 

 containing the precipitate was returned to the beaker also 

 previously dried over a flame, 100-200 cm3 of water, 5-10 cm3 of 

 strong hydrochloric acid, and O'5-l'O grm. of manganous 

 chloride were added, and the solution was titrated at 35°-40° 

 with permanganate. The results of the experiments, given in 

 Table VII, A, show that barium, either as the nitrate or 

 chloride, may be estimated in the manner described with a fair 

 degree of accuracy. 



* Ann. der Chem. (Liebig), xc, 102. f Bergman's Essays, i, 320. 



