406 



Messrs. L. Hill and M. Flack. 



[July 6, 



ready use of ozone for bleaching, sterilising water or ventilating purposes. 

 The ozone is generated by the electrical discharge of high-potential currents 

 across sheets of fine gauze set parallel and insulated from each other. The 

 gauze net ensures the equality of the discharge over the whole surface, and 

 prevents 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 concentrations far less than those used 

 by previous observers. 



Method of Estimation 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 litres of air have been passed through the 

 wash-bottle, the acidified KI is removed and freshly prepared pure starch 

 emulsion added. A blue eolour indicates the presence of ozone. The 

 amount is estimated by titration with sodium hyposulphite solution until 

 this blue colour is discharged. The hyposulphite solution is prepared by 

 dissolving 22 - 2 grm. in 1 litre 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 ten litre sample. For small quantities of ozone the solution may be diluted 

 10 or 100 times, giving 1 c.c. of the solution equal respectively to ten and 

 one part per million of ozone in the air collected. 



Lethed Dose of Ozone. — To determine this the animals were placed in a 

 large airtight chamber. The ozonised 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 necessary, be lighted by 

 electric light. Our experiments show that animals 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 (Edematous. Microscopically the 

 pulmonary alveoli appear full of an inflammatory exudation. Many of 

 the alveoli are full of blood, for so intense is the irritant effect that 

 hemorrhages cake place. There are no other signs of the effect of ozone 



* 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. 



