It could not be ascertained that any investigation of this matter had ever been undertaken. It was therefore decided to study the question and it appeared that the most satisfactory evidence could be obtained by measuring the quantity of oxygen which is evolved when potassium permanganate and manganese dioxide are brought together.
Description of Apparatus.
The apparatus[4] employed in this work consists of four parts:
“1) a flask, A, in which the reactions were conducted. A melting point bulb of about 40 cc. capacity, the diameter of its neck being 20 mm., was used for this purpose.
This was closed with a two-hole rubber stopper, through one hole of which passed:
2) A small glass tube, BB, running up from the flask about 40 cm., and then bent twice at right angles. One limb of this tube was surrounded by a small Liebig’s condenser, while the shorter turned down to meet—
3) a Schiff’s azotometer filled with mercury and connected at its top with the tube above mentioned. In practice it was found desirable to have a little water on the top of the mercury column.
4) Through the second hole of the rubber stopper closing the flask was passed a short piece of glass tubing bent obliquely just above the stopper and tightly connected with a rubber tube about 50 cm. long, DD. This tube was clamped near its lower end with a Mohr’s pinch-cock, while the upper was connected with the stem of a small funnel, F.
When an experiment was to be conducted, the azotometer C, was connected to the tube, B, and tied tightly, a piece of good rubber tubing being used for the connection. The reservoir of the azotometer, M, was then raised until the mercury had driven out all the air in C, and the stop-cock closed. Next the funnel F was filled with water, the pinch-cock closing D opened and the water allowed to flow down and drive out all the air in the tube. The latter was then clamped and thus kept full of water. The apparatus being now ready, the flask A, containing the substances in the desired quantity, was made fast to B and D by means of its stopper. The stop-cock of C opened. The flask A was heated in a water bath for any desired time, the oxygen being collected in C as fast as it was given off.