A SCHOOL IMITATION of DUMAS'S EXPERIMENT WILLIAM T. BROW George Heriot's School, Edinburgh, Scotland
T
HE following imitation of J. B. A. Dumas's mercury seal to &ow the hydrogen to escape in the famous experiment where the combining weights event of too great a pressure. The gas was passed of hydrogen and oxygen were determined has through a solution of silver nitrate, and then through been used with success in the laboratory classroom for potassium permanganate solution for purification, both the determination of the equivalent of oxygen. As a solutions being contained in Drechsel bottles. The class demonstration it gives an excellent result if the gas was then dried by passing i t over anhydrous calmanipulation is carefully canied out. The whole ex- cium chloride contained in three U-tubes. The hydroperiment may he carried out in approximately eighty gen now passed through a bulhed tube ( A ) blown from minutes, a great advantage since it can be completed a medium-walled piece of ordinary glass tubing, and during the time allotted in the classroom at one visit. then drawn out to a narrow end and bent a t right angles It demonstrates the careful manipulation of delicate as in sketch. The bulb was half filled with pure dry apparatus and serves as a good lesson in quantitative copper oxide wire and weighed without the rubber conmeasurement. nection but with the small rubber stopper (S) a t the The apparatus used was much less elaborate than narrow end. Most of the water fonped in this bulbed Dumas's, and the U-tubes employed were of ordinary tube by the combinationof the hydzog& with the oxygen of the oxide was trapped in an empty U-tube which may size. Hydrogen gas was made in a WoulB bottle contain- he surrounded by a freezing mixture. This U-tube ing commercial zinc and a dilute solution of pure sul- represents the hulhed tube used by Dumas for catching furic acid which had been previously boiled for a few the bulk of the water. The empty U-tube was weighed, minutes to expel air and gases. T h q e was the usual along with the next stoppered U-tubefilled with auhyHyd~o~cn
-+
td
-+
drous calcium chloride, the rubber connection between the two being left in position. A small rubber stopper was used to close the empty U-tube (B) to prevent evaporation of the water. A second stoppered U-tube filled with anhydrous calcium chloride was used as an absorber also, but this was weighed separately. Finally, the excess hydrogen was allowed to escape through a sulfuric acid trap which prevented moisture of the air entering the absorbers. Before weighing was begun all air was swept out of the apparatus, and the absorption tubes to be weighed were closed. The reducing temperature is low and, after sufficient water had been collected, the bulbed tube was allowed to cool down while the hydrogen gas was still being passed through. The bulbed tube was weighed both before and after the reduction filled with air, while the absorbers were weighed filled with hydrogen both times. After the apparatus had cooled to room temperature, the bulbed tube was allowed to stand in the balance case and weighed last to give the hydrogen time to escape.
REPRESENTATIVE EXPERIMENTAL DATA g.
+ +
Weight of bulbed tube copper oxide residue Weight of bulhed tube Weight of oxygen be for^ reduction: Weight of 2 absorbers Weight of 3rd absorber Total After reduction: Weight of 2 absarhers Weight of 3rd absorber Total Weight of water formed Weight of hydrogen
27.6275 26.3943 1.2332 38.4255 19.7732 58.1987 39.8135 19.7734 59.5869 1.3882 0.1550
0.155 g. of hydrogen combines with 1.2332 g. of oxygen.
.:
1 g. of hydrogen combines with
1n.2315.5 3'
= 7.95 g. of oxygen
or 16 g. of oxygen combines with 2.011 g. of hydrogen
An average of nineteen experiments by Dumas gave 16 arts bv weight of oxwen combine with 2.004 parts
MINUTES OF THE MEETING OF THE EXECUTIVE COMMITTEE OF THE DIVISION OF CHEMICAL EDUCATION The Executive Committee of the Division met in Pittsburgh on September 9th. Present: H. Hale (Chairman), N. W. Rakestraw, Virginia Bartow, R. A. Baker. It was voted to publish an abstract, if possible, of the recent report of the Committee on Chemical Education of the Non-collegiate Type, and to make the complete report available in mimeographed form. Dr. G. J. Esselen was re-elected to the Board of Publication. Secretary N. W. . .RAKESTRAW, MINUTES OF THE ANNUAL BUSINESS MEETING OF THE DIVISION OF CHEMICAL EDUCATION. A. C. S.
Prof. J. R Katz, of Amsterdam, Holland, George Fisher Baker Non-resident Lecturer at Cornell University last year. Prof. Katz is an international authority on the chemistry of starch and starch products. The above snapshot was taken by Prof. C. W. Foulk upon the occasion fof Prof. Katz's visit to Ohio State University in March, 1935.
The annual business meeting tobk place in Pittsburgh on September 10th. The following officers were elected: Chairman: 0. M. Smith Vice-chairman: E. W. Phelan Secretary: N. W. RakestrawExecutive Committee Member-at-large: M. V . McGill It was voted to appoint a committee to cooperate with the College Entrance Examination Board in formulating new requirements in chemistry. A vote of thanks was extended to the Pittsburgh Section in arranging for the meeting. Secretary N. W. RAKESTRAW,
