PHYSIOLOGICAL INFLUENCE OF OZONE—HILL AND FLACK. 619 
the electrical discharge of high-potential currents across sheets of 
fine gauze set parallel and insulated from each other. The gauze net 
insures the equality of the discharge over the whole surface, and pre- 
vents that excessive high-tension discharge at certain rough points, 
which occurring in the older form of instruments fitted with smooth 
metal plates, causes the production of oxides of nitrogen from the 
burning of atmospheric nitrogen.!. Our object therefore has been to 
determine the effects of undoubtedly pure ozone, especially in con- 
centrations far less than those used by previous observers. 
Method of estumation of concentration of ozone-—The air containing 
ozone is sucked by an aspirator or filter pump through a 1 per cent 
solution of potassium iodide, acidified with a small quantity of 10 
per cent sulphuric acid contained in a Drechsel wash bottle. It is 
essential that contact with rubber be avoided. After 10 liters of air 
have been passed through the wash bottle, the acidified KT is removed 
and freshly prepared pure starch emulsion added. A blue color indi- 
cates the presence of ozone. The amount is estimated by titration 
with sodium hyposulphite solution until this blue color is discharged. 
The hyposulphite solution is prepared by dissolving 22.2 grams in 
in 1 liter of distilled water, so that 1 c. c. of the solution is equivalent 
to 100 parts per million of ozone in the air collected as a 10-liter 
sample. For small quantities of ozone the solution may be diluted 
10 or 100 times, giving 1 ¢. c. of the solution, equal, respectively, to 
ten parts and one part per million of ozone in the air collected. 
Lethal dose of ozone.—To determine this the animals were placed in 
a large air-tight chamber. The ozonized air was then driven through 
by means of a gas engine driving an air pump, and the concentration 
of ozone determined in the issuing air. ‘The animals could be observed 
through the glass windows of the chamber, which could also, if neces- 
sary, be lighted by electric light. Our experiments show that ani- 
mals may die after being submitted to 15 to 20 parts per million for 
two hours. We do not doubt that a lower concentration would have 
a fatal effect if breathed for a much longer period. 
The cause of death is acute inflammation of the respiratory tract. 
The lungs become intensely congested and cedematous. Microscopic- 
ally the pulmonary alveoli appear full of an inflammatory exudation. 
Many of the alveoli are full of blood, for so intense 1s the irritant effect 
that hemorrhages take place. There are no other signs of the effect 
of ozone in the body.~ On inhaling ozonized air ourselves and. expir- 
ing through the iodine test solution we find no evidence of ozone in 
the exhaled air. It is all taken up by the wet mucous surface of the 
respiratory tract and exerts its effect there. 
1 Mr. Edward L. Joseph, the inventor of the “Ozonair” apparatus, was good enough to give us the use 
of a complete installation and place his information at our disposal. 
