A STUDY IN THE DETERMINATION OF CALCIUM. 
BY GEORGE HEISE. 
In this series of experiments it has been attempted to simplify the 
gravimetric determination of calcium, to make it a more satisfactory 
and convenient laboratory method. 
The precipitation of calcium as the oxalate and its subsequent con- 
version by heating to the oxuie is a method which presents some diffi- 
culties, especially to the inexperienced student. To entirely convert all 
the calcium to the oxide is a long and tedious process- at best, besides, 
especially when porcelain crucibles are used, it is almost impossible to 
heat the oxide down to constant weight. 
It occurred to us that it might be feasible to precipitate calcium as 
the oxalate in the usual manner, to filter it through a Gooch crucible, 
to weigh it directly as the oxalate, or to change the oxalate to the car- 
bonate by careful heating, and to weigh as the carbonate. 
A careful search through the literature revealed only one article^ in 
which the conversion of the oxalate into the carbonate by heating is 
recommended as a method for the gravimetric determination of calcium 
(Strentium, Barium). The heating was done in a capped Gooch crucible 
over a free Bunsen flame. No precautions or special directions were 
given and the results, though fairly accurate, were low in each case, 
showing the partial decomposition of the carbonate into the oxide. 
It shall be my endeavor to shoAV hoAV calcium may be determined 
directly as the oxalate in a Gooch crucible and hoAV the oxalate may be 
converted into the carbonate by heating Avithout danger of loss by de- 
composition. 
A carefully weighed amount of the purest obtainable calcite was 
introduced into a graduated litre flask, covered Avith dilute HCL and 
allowed to decompose. The^ flask Avas then filled to the mark with' water. 
The solution, Avffiich Avas perfectly clear and free from residue, was kept 
in a glass-stoppeed bottle and convenient quantities for analysis Avere 
AvithdraAAm as needed by means of a* graduated pipette. 
*Estimation of Calcium, Strontium and Barium as the Oxalates (Avith KMNO). 
Am. Jour. Sci. Series 4-1. (1901) 216. 
