STERILIZATION OF DRINKING WATER COURMONT. 239 



EXPERIMENTS SHOWING TIIE STERILIZING OF WATER BY THE ULTRA- 

 VIOLET RADIATIONS. 



The sterilization of the water is complete, no matter how polluted 

 it may have been, provided that it is still transparent to the ultra- 

 violet rays. The ultra-violet rays can therefore absolutely free from 

 germs water far more polluted than is ever the case with the natural 

 water which in practice requires purification. 



The experiments by means of which Th. Nogier and myself have 

 shown that the sterilization is complete are simple and may be 

 summarized in a few words. We have had built above our laboratory 

 a reservoir holding some 60 liters, filled with city water, but into 

 which we could introduce all the impurities with which we wished to 

 experiment — colon bacilli, typhoid-fever bacilli, solutions of fecal 

 matter, etc. It has often happened that the watei contained up to 

 1,000,000,000 colon bacilli per cubic centimeter, whereas the most 

 impure natural water rarely contains more than 1,000. Our experi- 

 mental conditions were therefore very exacting, far more so than 

 would ever occur in practice. 



The water from the reservoir passed either into our cylindrical box 

 or into another piece of apparatus devised by Nogier. In the former 

 (fig. 2) (135 volts, 4 to 9 amperes) the sterilization was complete in 

 several seconds, a minute at the longest. Indeed, the sterilization 

 was practically almost immediately accomplished, but we wished an 

 absolute sterilization, for instance, not a single colon bacillus in a 

 liter of previously infected water. This required* sometimes a minute 

 (at 0.30 meter from the lamp). 



The details of the apparatus designed by Nogier were somewhat 

 different; the water flowed without stopping at the rate of 400 to 500 

 liters per hour (it could go as fast as 1,000 liters) but passed as a thin 

 layer about the lamp. Such would be the conditions of daily use. 

 With Nogier's apparatus sterilization took place almost immediately 

 and was complete. The water, contaminated as above described, 

 came out absolutely free from germs. One could pollute a liter and 

 more and not a single microbe colony would remain. 



These truly surprising results were in all points accurate. They 

 have been verified by all those who, following our experiments, have 

 taken up the study, Miquel, 1 Cernovodeanu and V. Henri, 2 Vallet, 3 

 and others. These conclusions are now well known. 



The following results were obtained by Miquel who investigated 

 this method for the city of Paris. Like us, Miquel polluted artificially 

 the water upon which he experimented (apparatus of fig. 3). In 

 Tables I and II are given two of his tests using colon bacilli. 



1 Miquel. Rapport au Prefet de la Seine, 1909. 



2 Cernovodeanu et V. Henri, Etude de l'action des rayons ultra- violets sur les microbes. Ac. des Sciences, 

 3 Janvier 1910. 



3 Vallet. Ac. des Sciences, 7 mars 1910, 25 avril 1910. 



