76 
FIFTEENTH REPORT. 
come from the West Washington Street Station of the Ann Arbor 
Water Company. 
Yours truly, 
(Signed) R. W. FRYER, 
Assistant in Hygiene, University of Mich. 
BOILING WOULD DO THE SAME BUT WHAT OE THE COST. 
There are several wavs for the production of ozone but the only one 
of commercial importance is by means of an electric discharge. The 
production of an appreciable amount of ozone requires the use of from 
eight to ten thousand volts at the least and most plants operate at a 
much higher voltage. The essential principal is the same in all types 
of ozonizers. that is, one pole is grounded while the other is connected 
directly to the step up transformer. Between these two poles is a dielec- 
tric or nonconductor of air, glass, shellac, mica or some similar sub- 
stance. When a high tension alternating current is turned through 
such an apparatus as I have roughly described the discharge takes place 
between these poles and through the dielectric and is usually referred 
to as the silent or brush discharge although just what this really is 
would be very hard to define. This discharge is characterized by a 
peculiar bluish-violet radiation and it is said that the production of 
ozone from the oxygen of the air, which passes between the poles and 
the dielectric, is due to the presence in this discharge of ultra-violet 
light. 
It has been found by careful investigation that there are several 
factors that greatly influence the economical production of ozone. 
1st. The concentration of ozone should not be carried too high be- 
cause it takes more current proportionally to increase the concentra- 
tion beyond three than it does to operate on a larger volume of air 
and to have a lower concentration of ozone. By concentration is meant 
the weight in gramms of actual ozone in a cubic meter of air. 
2d. The air to be ozonized should lie dry otherwise there will be 
some peroxide of hydrogen formed which would remain in the water 
and also the output of ozone for a given expenditure of electric energy 
is lowered. 
3d. The temperature should be low in order to obtain maximum con- 
centration with minimum current. 
Ozone is practically insoluble in water and this fact makes it a 
good agent for purification because of the ease of removal but a poor 
one on account of the difficulties of obtaining a good mixture. Many 
schemes have been devised to secure a good mixture or emulsion among 
them being the De Frise sterilizing towers which are divided into sec- 
tions by baffling plates with very small (1-140 of an inch) holes. In 
these towers the water usually comes in at the top and moves downward 
while the ozonized air comes in at the bottom and moves upward. In 
another system the towers are filled with small pebbles and the water 
is sprayed over the top while the ozonized air comes in at the bottom. 
Another system, which I do not think has met with much success, 
depends upon an aspirater or water pump and sucks the ozonized air 
through by the aid of the water which is to be purified. Still another 
