IOWA ACADEMY OF SCIENCE 
137 
TABLE I. 
DETERMINATIONS IN PORCELAIN GOOCH CRUCIBLES. 
Number 
Weight 
of 
Oxalate 
Calcu- 
lated 
Weight 
Error 
Weight 
of Car- 
^ honate 
Calcu- 
lated 
Weight 
Error 
1 _ 
0.4870 g 
0.4867 g 
+ .0003 g 
0.3850 g 
0.3802 g 
+ .0048 g 
2___' 
.4870 g 
.4867 g 
+ .0003 g 
.3830 g 
.3802 g 
+ .0028 g 
3 
.4875 g 
.4867 g 
+ .0008 g 
.3818 g 
.3802 g 
+ .0016 g 
4 
.4870 g 
.4867 g 
+ .0003 g 
.3816 g 
.3802 g 
+ .0014 g 
5 1 _ 
.1942 g 
.1947 g 
—.0005 g 
.1510 g 
.15209 g 
—.0011 g 
.1947 g 
.1526 g 
.15209 g 
+ .0005 g 
Note. — Calculations are based on weight of calcite. 
The first preliminary determinations having succeeded so well, the 
second series was begun, this time in a platinum Gooch, to make pos-' 
sible the weighing of calcium not only as the oxalate and carbonate, 
buc also as the oxide. Thus a double check on the accuracy of the work 
could be secured. In this series it. was likewise attempted to devise a 
clean-cut and efficient method of converting the oxalate into the car- 
bonate, without necessitating the weighing as oxide to check results. 
Most teachers would hesitate to advocate weighing of calcium as the 
carbonate unless more certain and specific directions for the conversion 
of the oxalate could be laid down. 
The oxalate was precipitated in the usual manner and weighed in a 
covered Platinum Gooch crucible. For the conversion to the carbonate 
the following scheme was devised : 
The Gooch crucible was placed on a thin piece of asbestos in a large 
iron crucible. The iron crucible was then covered with a porcelain cover 
and heated to the highest possible temperature over a full Bunsen flame. 
The results obtained were as accurate as could be wished for. Heating 
by this method for 20-30 minutes brought the carbonate down to constant 
weight and eliminated all danger of decomposition by superheating. 
As an added check the carbonate was converted to the oxide in a blast 
lamp, using a capped platinum Gooch, yielding results concordant with 
the calculated value in each case. 
The second series follows: 
