STERILIZATION OF DRINKING WATER—COURMONT. 239 
“EXPERIMENTS SHOWING THE 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 afew 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 water 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,! Cernovodeanu and V. Henri,? Vallet,' 
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 Préfet 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. 
