Barium, as the Oxalates. 



219 









Table IV. 













Volume during titration 



150-250 cm3 







SrO, 





Volume 











taken 



Ammo- 



at 



Propor- 



Acid 







as 



nium 



precipi- 



tion of 



present 



SrO 





3r(X0 3 ) 2 . 



oxalate. 



tation. 



85$ 



during 



found. 



Error. 



grm. 



grm. 



cm 3 . 



alcohol. 



titration. 



grm. 



grm. 



00974 



0-4 



100 



JL 



HC1 



0-0973 



—o-oooi 



a 



u 



a 



u 



a 



0-0983 



+ 0-0009 



u 



u 



u 



'< 



u 



0-0975 



4-0-0001 



a 



0*8 



tc 



U 



u 



0-0981 



+ 0-0007 



0-1948 



0-4 



200 



u 



a 



0*1943 



— 0-0005 



c< 



0-8 



a 



u 



(C 



0-1942 



-0-0006 



0*0974 



0-4 



100 



i 



H.SO. 



0-0970 



— 0-0004 



ti 



tc 



cc 



1 

 5 



a 



0-0977 



+ 0-0003 



a 



a 



u 





u 



0976 



+ 0-0002 



0*1948 



0-6 



150 



(C 



« 



0-1938 



— 0-0010 



In the last experiment in which a comparatively large 

 amount of strontium salt was present and the dilution low, 

 there is a slight tendency towards a minus error due probably 

 to the occlusion of some oxalic acid by the strontium sulphate 

 formed. This phenomenon would favor titration at greater 

 dilution when sulphuric acid is used to liberate the oxalic acid 

 from large amounts of strontium oxalate. 



Precipitation in Water Solution. — In order to determine 

 the degree of precipitation of strontium salts in water solution, 

 0*0974 grm. of strontium oxide, taken as the nitrate, was pre- 

 cipitated by ammonium oxalate, the mixture was allowed to 

 stand over night, filtered on asbestos, the precipitate was 

 washed with water containing one-half of its volume of 85 per 

 cent alcohol, treated in the capped crucible with a few drops 

 of sulphuric acid, ignited, and weighed as the sulphate. The 

 result gave 0-0973 grm. of strontium oxide. The precipita- 

 tion, therefore, of strontium oxalate, in water solution with a 

 sufficient excess of ammonium oxalate present, is practically 

 complete. 



To determine the amount of ammonium oxalate necessary 

 for the precipitation of strontium salts in water solution, 

 experiments were made in which strontium oxalate was pre- 

 cipitated in the presence of varying amounts of ammonium 

 oxalate, allowed to stand over night, the clear liquid was 

 decanted on asbestos, and the precipitate was washed two or 

 three times with l0-20 cm3 of cold water. The results obtained 

 by the estimation of the oxalic acid by permanganate show 

 that an amount of ammonium oxalate several times larger than 

 that required for the theoretical formation of strontium oxalate 

 is necessary for the separation of the strontium oxalate. The 

 experiments are recorded in Table V. 



