218 Peters — Estimation of Calcium, Strontium and 







Table II. 







SrO, 





Volume 



Volume 



SrO, 





taken as 



Ammonium 



at 



of 



found 





Sr(NO s ) 2 . 



oxalate. 



precipitation. 



alcohol. 



as SrS0 4 . 



Difference. 



grm. 



grm. 



cm 3 . 





grm. 



grm. 



0-2434 



0-8 



180 



* 



0-2440 



+ 0-0006 



0-2434 



0-8 



a 



u 



0-2437 



+ 0-0003 



0-0022 



0-2 



100 



u 



0-0022 



o-oooo 



0-0013 



0-2 



« 



« 



0-0014 



+ 0-0001 



0-0004 



0-04 



a 



a 



0-0004 



0-0000 



ments were made using varying proportions of 85 per cent 

 alcohol with different amounts of ammonium oxalate, and the 

 nitrates from such experiments were tested for strontium by 

 the addition of more alcohol. 



The results are given in Table III. 







Table III. 







SrO, 









SrO found 



present 





Volume 



Proportion 



in filtrate, 



as 



Ammonium 



of 



of 85 % 



weighed 



Sr(N0 3 ) 2 . 



oxalate. 



liquid. 



alcohol. 



as SrS0 4 . 



grm. 



grm. 



cm 3 . 





grm. 



( o-i 



0-4 



100 



i 



o-oooo 



J u 



a 



« 



JL 



1 



o-oooo 



1 " 



a 



<t 



"A 



0-0004 



(0-1 



0-2 



a 



i 



o-oooo 



\ " 



a 



a 



TTT 



0-0009 



I " 



a 



a 



I 



0-0020 



loa 



o-i 



cc 



3 



0-0002 



The results in Table III show that when a moderate excess 

 of ammonium oxalate is present, a volume of 85 per cent 

 alcohol, amounting to one-fifth of the whole, is sufficient to 

 complete the precipitation of the strontium as the oxalate. 



The conditions under which strontium oxalate is insoluble 

 having been determined, the process for the volumetric estima- 

 tion of strontium was carried out as follows : The hot solution 

 of a strontium salt was precipitated with ammonium oxalate, 

 85 per cent alcohol, amounting to from one-fifth to one-third the 

 total volume, was added, the mixture was allowed to stand over 

 night, and the clear liquid was decanted on an asbestos filter. 

 The precipitate was washed with a mixture of equal parts of 

 85 per cent alcohol and water, transferred to the filter, dried in 

 the filtering crucible over a flame to free it from alcohol, 

 returned to the beaker previously dried, treated with sulphuric 

 acid, or with 5-10 cm3 of hydrochloric acid (in the latter case 

 O'5-l'O gm., of a manganous salt being added) and the liberated 

 oxalic acid was titrated by permanganate. The results obtained 

 by this method are accurate and are given in Table IV. 



