STIRRING AS A TIME SAVER IN GRAVIMETRIC ANALYSIS. 
W. M. BLANCHARD. 
While making experiments recently on the deposition of metals with a 
rotating anode, it occurred to me that various gravimetric analyses might 
be greatly facilitated by rapid stirring of the precipitate. That stirring 
greatly facilitates precipitation is known to every one, but I do not know 
that any data have been recorded to show just how efficient the stirrer may 
be, hence these experiments. These results are very surprising. 
A stirrer was made from a small glass rod about two millimeters in 
diameter. It had the shape of the letter T, the arms, each about eighteen 
millimeters long, being flattened at the ends and turned so as to resemble 
an ordinary propeller. The stem was about ten centimeters long and was 
attached to a wheel run by a small electric motor, which in turn was con- 
nected with an ordinary 110 volt lighting circuit. There was thrown in 
the circuit a small lamp bank so that the speed of the motor might be 
varied. The following analyses were carried out with the stirrer making an 
average of 900 revolutions per minute. 
1. Hstimation of bariwm in crystallized barium chloride. The sample 
of the pure salt, 0.2330 gram, was weighed out in a 150 c. ¢. beaker, diluted 
to about 50 ¢.c¢., acidified with hydrochloric acid, heated to the boiling 
point, treated with slight excess of dilute sulphuric acid, stirred four min- 
utes, immediately filtered, washed, ignited, cooled, and weighed. Found 
for barium 56.25%; calculated, 56.23. 
2. Hstimation of calcium in pure calcium carbonate. A small sample 
of the purest calcium carbonate, 0.2225 gram, was transferred to a 150 ¢. c¢. 
beaker, converted into the chloride, diluted to about 50 ¢.¢., heated to boil- 
ing, treated with slight excess of ammonium oxalate, made alkaline with 
ammonia, stirred four minutes, then filtered, washed, ignited, heated over 
the blast lamp, cooled and weighed. Found for calcium oxide 56.04% ; 
calculated 56.03. 
3. Estimation of copper in cupric sulphate. A small sample of re- 
crystallized pure sulphate, 0.2000 gram, was weighed in a 150 c. c¢. beaker, 
