5 Proceedings of Indiana Academy of Science 
of the annular discharge space was approximately 3 mm., the outside 
diameter of the inner glass tube being 33.5 mm., and the length of the 
discharge space, 50 cm. The volume of the discharge space was found 
by actual measurement to be 166 cc. The inside tube was filled with 
acidulated water, and this together with a spiral of No. 18 copper wire 
placed inside the tube acted as the high tension electrode. The water 
surrounding the tube, which was made conducting by the use of NaCL, 
was grounded through the medium of the-metal containing tank con- 
nected to the ground. A spiral of wire was wound around the out- 
side of the discharge tube and connected to ground to insure even dis- 
tribution of voltage over the entire length of the tube. 
Absorption apparatus consisting of broken glass tubing placed in- 
side a tower was connected as shown in Fig. 1. Sodium hydroxide was 
used in most cases as the absorbing liquid. In some cases the gases 
were passed through a KI solution from which the ozone yield could 
be determined by titration with sodium thiosulphate. The inlet and 
outlet tubes were provided with stop cocks so that the tube could be 
completely closed and the pressure of the gas in the discharge tube 
measured by the mercury manometer. Alcohol thermometers were 
placed in the liquid inside the inner tube of the discharge tube and in 
the cooling water surrounding the tube. Means were provided whereby 
dry air could be passed through the discharge space, the air having 
been dried by the use of sulphuric acid, after which it passed through 
a chamber containing soda lime. 
Two sources of power were provided for producing the required 
electric potential to break down the air in the space between the two 
tubes, one of these being a large induction coil and the other a high 
voltage transformer. The induction coil was operated from a 110-volt 
direct current source and was provided with a rheostat in series for 
varying the high tension voltage. This coil is capable of delivering a 
spark between needles of more than 30 cm. in length. The high ten- 
sion transformer, rated at 50 kva. 200,000 volts, was connected to an 
alternator giving practically a sine wave. This transformer has been 
arranged so that the current in the secondary winding may be read 
directly. The high tension voltage was determined by calibrating the 
tertiary coil, with which the transformer was provided, against the 
sphere gap standard of the A. I. E. E. 
TESTS ON ENCLOSED VOLUMES OF DRy AIR. 
All of the tests which will be reported in this paper were made 
upon enclosed volumes of dry air, using either the induction coil or 
the high tension transformer. Only tests which are more or less typi- 
cal will be given here, and represent but a small part of the total 
number of tests made. Correction for pressure change due to in- 
crease of temperature as the run progressed was not made, although 
in many cases the temperature rise curve is shown, this temperature 
being invariably that of the inner electrode. The temperature of the 
outside of the tube did not change materially on account of the large 
body of cooling water which was agitated frequently. 
