U6 



Gooch and Eddy — Separation of Magnesium. 







Tabli 



: I. 







MgO 

 taken as 

 MgCla 



MgO 

 weighed 



Error 

 MgO 



MgO found as 



MgoP,0 7 in 



filtrate 



Volume 

 of precip- 

 itant 



Volume of 

 reagent 

 used in 

 washing 



grms. 



grm. 



grm. 



A. 



— 0-0029 



grm. 



cm 3 . 



cm 3 . 



0-0029 



0-0000 



0-0024 



100 





0-0289 



0-0286 



— 0-0003 



0.0007 



10 





0-1444 



0-1430 



— 0-0014 



0-0006 



50 





0-1444 



0-1427 



— 0-0017 



0-0009 



50 



50 



0-0034 



o-oooo 



B. 

 — 0-0034 



0-0033 



100 





0-0342 



0-0342 



— 0-0000 



0-0002 



10 





0-1708 



0-1694 



— 0-0014 



0-0012 



50 





0-1708 



0-1696 



— 0-0012 



0-0012 



50 





0-1708 



0-1698 



—o-ooio 



0020 



50 



25 



0-1708 



0-1683 



— 0-0025 



0-0024 



100 



10 



0-1708 



0-1670 



-0-0038 



0-0043 



200 



10 



These experiments show plainly that ammonium magnesium 

 carbonate is noticeably soluble in Schaffgotsch's solution of full 

 strength, and rather more so in the same reagent of half strength. 

 So, it is evident that an exact separation of magnesium from 

 the alkalies, in solutions of reasonable volume, cannot be made 

 without some modification of the method. The effect of add- 

 ing to the mixture certain proportions of alcohol was therefore 

 tried, and, after some preliminary attempts, a series of experi- 

 ments was performed for which the precipitant used was made 

 by saturating with ammonium carbonate a mixture of 180 cm3 

 of ammonium hydroxide, 800 cm3 of water, and 900 cm3 of absolute 

 alcohol, and filtering, after some hours, from the undissolved 

 ammonium carbonate. In the experiments of Table II (A), por- 

 tions of the standard solution of magnesium chloride were evap- 

 orated nearly to dryness and to the residue was added a definite 

 amount of the alcoholic solution of ammonium carbonate. The 

 precipitates, after stirring and standing over night, were fil- 

 tered upon asbestos in the perforated platinum crucible, washed 

 with the precipitant, dried, ignited strongly, and weighed. The 

 filtrates were examined as before for dissolved magnesium by 

 the phosphate method. In the experiments of Table II (B) an 

 equal volume of alcohol was added to the solution of magnesium 

 chloride taken and to this mixture was added, as a precipitant, 

 a volume of the saturated alcoholic solution of ammonium car- 

 bonate equal to that of the magnesium chloride. The precipi- 

 tate was filtered, washed, dried, ignited, and weighed as in the 

 former experiments. The filtrate was examined as before for 

 magnesium. 



