Siemens Ozonizer 175 
utes sooner than in the first run. The concentration of NO at the end 
of the first run, at a pressure of —42.5 mm. was 2.3 compared with a 
concentration of 9.35 per cent NO at —42.0 mm. Here the pressures 
are practically the same and yet the products are quite different. Sev- 
eral runs were made later in the attempt to check the cyclic change in 
this run, but without success. 
Another run under the same conditions was made and stopped at 
the reversal point, which occurred at 130 minutes with an NO concen- 
tration of 9.9 per cent, the tube current being 3 milliamperes compared 
with 4 and 4.5 milliamperes for the first two runs. Although 34 runs 
were made, following these first two runs, yet in every case the con- 
centrations were much lower than in these first two runs. 
Using the transformer supply, the curves shown in Fig. 4 were 
taken, the high tension voltage being held constant. The same reversal 
occurred here as before, but the pressure increased very rapidly after 
reversing and at the end of the run a concentration of 0.363 per cent 
NO was obtained. The second test with alternating current (D-8), re- 
versed at a pressure about 7 mm. higher than did D-7, but the reversal 
in both came at 50 minutes. The concentration at reversal with alter- 
nating current was 2.48 per cent NO, which is considerably less than 
was obtained with the induction coil. The variation of the tube cur- 
rent should be noted since the current curve follows the pressure curve 
more or less in shape. Another run with the transformer was made at 
31 cycles, which was as near the 25 vibrations per second of the induc- 
tion coil as could be obtained. The pressure in this run reversed at 
53 mm. below the initial pressure of 740 mm. after an exposure to the 
discharge for 110 minutes. The concentration at this point was 3.21 
per cent NO. 
From these results it is clear that the yield of nitric oxides, which 
may be discovered by the titration of NaOH for the determination of 
acid formed, is not proportional to the pressure decrease as might be 
expected. To get some idea of the concentration for different times of 
exposure to the discharge with both the induction coil and the alter- 
nating current, a series of runs were made which are tabulated in 
Table I. 
TABLE I. 
Concentration 
No. Length of Pressure Decrease Percent NO. at ~~ 
D— Run (min.) at end of run end of run per mm. per min. 
(mm.) 
| 
Inducticn coil ruans—Frequency—25 
13 10 —12.5 0.073 0.0058 0.0073 
14 20 —16.5 1.00 0.062 0.05 
14.5 40 —25.5 1.88 0.074 0.047 
15 60 —34.0 2.12 0.082 0.035 
Alternating Current Runs— 
Frequency—31 
10 10 —12.0 1252, 0.127 0.152 
11 20 —17.5 1.91 0.109 0.09 
12 40 —26.0 2d 0.081 0.07 
Although the average current for the alternating current runs 
listed in Table I was less than for the induction coil runs, yet the 
