130 STERILIZATION AND DISINFECTION 
A. The ultra viokt rays produced by the Cooper Hewitt mercury 
arc have a_ strong 
bactericidal power. 
B. Certain varieties 
of bacteria in aqueous 
suspension, including 
spore-forming organ- 
isms, are killed by 
exposure to the rays. 
Molds. however, are 
only partially de- 
stroyed by the ultra 
violet light. 
C. The action seems 
to be photo-mechani- 
cal and is in all proba- 
bility due to absorp- 
tion of ultra violet 
rays by bacterial pro- 
toplasm. 
D. Proteins and 
other bodies of high 
molecular weight in- 
terfere with the action 
of the rays. Turbidity, 
both organic and in- 
organic, has a similar 
action. Color within 
certain limits seems 
to have no action. 
Ultra violet light 
was first used for the 
sterilization of milk 
280 =. 300 
260 
240 
i) 
ol 
G1 
160 180 200 
Seconds 
140 
120 
100 
(After von Recklinghausen, 1914.) 
60 
and 3 5 Amperes. 
SD ne et ee ae ee ee ee ee 
rr es ae ae ! 
| I ! 
Pietehoy pt tt bE TP tg 
PE db tp db yb et 
Pep th ho pp by bd 
Ppa bd te bbb by di 
t , to ! 1 | * ‘ . . 
es: ee PEt tt and since this time its 
t¢ i: oy, 4 roned a | i oat 
pi idk i (BEB use has been extended 
eReeS BEI BE | to other materials. 
wm ! Mm ' & om ” 
Befeo (PE SER te Von Recklinghausen 
Ps) cr ta 8 —~ @ | Oo Foy * ° 
sebS5 122228 fd Eg | studied the action of 
Bases Bee PRES Bas | ultra violet light on 
He meh OR So GRR ee go a . . 
SS STSC SESE ee yao RES bacteria in water. 
MAMA MOM OMe Aa 
30 
Fie. 42.—Seconds Necessary to Kull Different Types of Microorganisms at 200 mm. from a Quartz Lamp Burning at 66 Volts 
Spores are said to be 
