1Q8 Philippine Journal of Science 1919 



2. By determining some other constituent and calculating to calcium 

 carbonate. 

 By evolution of carbon dioxide. 



Absorption in soda lime or alkali hydroxide solution. 

 Loss in weight due to evolution of gas from Geissler's or simi- 

 lar apparatus. 

 Loss on ignition. 

 Hydrometer apparatus. 

 Monometer apparatus. 

 Calcimeter. 

 By titration methods. 

 By determining acid-insoluble material. 



Determination of calcium by precipitation as calcium oxal- 

 ate. — Most of the methods depend on the fact that calcium may 

 be precipitated from solutions of its salts by the addition of am- 

 monium oxalate. The solution may be titrated directly with 

 standard oxalate solution, 2 or an excess of oxalate may be added, 

 the precipitate collected and the amount remaining uncom- 

 bined with the excess oxalate titrated with potassium per- 

 manganate. 3 Calcium oxalate may be dried and weighed; 4 

 may be ignited to the oxide,' carbonate/ or sulphate ; r or may be 

 dissolved in sulphuric" or in hydrochloric acid," and titrated 

 with potassium permanganate. It may be also determined by 

 the Fox 10 photometric method. 11 



Determination of calcium without the use of ammonium 

 oxalate. — The methods include precipitation as the iodate, 12 the 

 tungstate, 13 the arsenate, 14 and the carbonate. 15 According to 

 Knobloch, 16 calcium may be determined by adding ferric chloride 

 and zinc iodide solutions, and titrating the iodine liberated with 



2 Prunier, Journ. Chem. So'c. 48 A2 (1885) 296. 

 ■ Kraut, Chem. Centralbl. 1 (1856) 316. 



* Fresenius, C. R., Quantitative Chemical Analysis. New York, John 

 Wiley and Sons 1 (1904) 272. 



"Fritzshe, Zeitschr. f. Anal. Chem. 3 (1864) 179. 



* Fresenius, op. cit. 273. 

 7 Fresenius, op. cit. 272. 



s Mohr, Titrirmethodc, ed. 7, 239. 



Peters, C. A. ; Am. Journ. Sci. 12 (1901) 216. 



M Hines, J. I. D., Journ. Am. Chem. Soc. 22 (1900) 269. 



" For other comments on methods involving the use of ammonium oxalate, 

 see Young, R. F., and Baker, B. F., Chem. News 86 (1902) 148, and Pagireff, 

 W., Journ. Chem. Soc, 82 A2 (1902) 356. 



11 Sonstadt, E., Chem. News 29 (1874) 209. 



1S Saint-Sernin, A., Compt. Rend. 156 (1913) 1019. 



14 Fox, P. J., Journ. Ind. Eng. Chem. 5 (1913) 910. 



"Forte, O., Journ. Chem. Soc. 66 A2 (1894) 322. 



"Knobloch, J., Journ. Chem. Soc. 68 A2 (1895) 326. 



