STERILIZATION OF DRINKING WATER COURMONT. 



241 



Bacillus mesentericus ruber, whose refractory spores will resist the 

 temperature of boiling water sustained for several hours." In Table 

 III is given a typical example of his results. 



Table III. — Sterilization of water 'polluted with Bacilli mesentericus. 



Thus, with water polluted with 128,200,000 bacilli per liter and 

 whose spores will resist boiling for several hours, sterilization is almost 

 immediate (in the time necessary for the water to pass through the 

 apparatus at the mean rate of 81 liters per hour. This experiment 

 should be of special interest to surgeons. 



Such are the results. Let me repeat my earlier conclusions, which 

 have been but strengthened: The sterilizing power of the ultra- 

 violet rays emitted by a quartz mercury-vapor lamp immersed in 

 water, face to face with the microbes contained in that water, is so 

 great that the problem of the integral, rapid, and economical steril- 

 ization of clear water by this procedure may be considered as solved. 



MUST THE QUARTZ MERCURY- VAPOR LAMP BE IMMERSED IN THE WATER ? 



Should the lamp be immersed in the water or merely placed just 

 above it ? Immersion is certainly preferable. 



Naturally we tried an apparatus in which the mercury-vapor 

 lamp was placed just above a thin sheet of water for sterilization. 

 The water was sterilized. However, practically and economically, 

 immersion is necessary. The reasons for this are easily given. 



The greatest reason is that the utilization of the sterilizing power 

 of the lamp is infinitely more perfect when within the mass of water 

 itself. The water is then in close contact with the source of the rays; 

 all of the rays emanating in all directions are used. A lamp conse- 

 quently sterilizes a far greater volume of water when it is immersed 

 than when merely placed close to the water — that is surely clear. 

 Economically, therefore, immersion is very advantageous. 



And yet further: Immersion seems necessary for the life of the 

 lamp as an emitter of ultra-violet rays. The quartz tube of such a 

 lamp, working in the air, is warmed to some 700° or 800° C. H. Bor- 

 38734°— sm 1911 16 



