AN IMPROVED HULETT APPARATUS FOR THE DEMONSTRATION OF THE VOLUMETRIC COMPOSITION OF WATER*
In the demonstration of the volumetric composition of water using the usual form of apparatus designed by Hulett, two difficulties have been encountered: first, the preparation of the electrolytic gases proceeds so slowly that only one determination can be made before a class during the lecture hour and this determination almost uniformly yields unsatisfactory results which makes the demonstration worthless; and second, the steam jacket is uniformly too low in temperature to insure the maintaining of the water formed as a vapor. The modifications adopted meet both of these objections satisfactorily, as is indicated by the results of a series of experiments quoted hereinafter. The first modification is the introduction of a super-heater between the steam flask and the jacket. This is made of pyrex tubing, 18" by I,", and heated by four Bunsen burners as indicated in the figure. It was
a t first thought that this method of heating would be irregular and thus spoil the results, but upon careful study using a thermometer inside the jacket it was found t h a t the jacket temperature remained constant * From a paper read before the Section of Chemical Education, Pittsburgh Meeting, A. C. S., 1922.
through the series of experiments run during an hour. The addition of a super-heater was, therefore, found t o be very advantageous in preventing condensation of water vapor formed during the experiments. The second modification is the use of a gasometer composed of a threeliter glass flask which is filled quickly with two liters of hydrogen and one liter of oxygen and connected with a siphon tube dipping into a large pneumatic trough so that water is admitted as rapidly as gas is withdrawn. Having thus a ready supply of mixed gases i t is quite easy to run a series of determinations before a class in a very short time. The two modifications have been in use a t Tulane University in the lecture demonstrations of general chemistry and have proved very satisfactory as the data will show.
Run "0.
A. Vol. of
B. Val. of gas after
Calculated
gasee.
exploo. actual cc.
decrease 2/3 A,
DiEerence actual-cala.,
C".
CE.
CC.
mired
Several other mixtures have been run with equally satisfactory results.
