COMPARATIVE EFFICACY OF DISINFECTANTS 



prevent putrefaction do not kill the bacteria, they only arrest growth and 

 multiplication. 



II. LETHAL VALUE FOR SPOKELESS TUBERCLE BACILLI. 



% 



Inferior lethal coefficient ; the time is given in which tubercle bacilli 

 (from cultures, not in sputum) are killed. From Yersin (54). 



Carbolic acid 



,, ,,..... 

 Absolute alcohol .... 



lodoform 



Ether 



Corrosive sublimate 



Thymol 



Salicylic acid 



To kill the bacteria in sputum, where they are embedded in mucus, 

 a much longer time is necessary, e.g. 10 per cent, lysol for twelve hours. 

 The figures in the table were obtained by mixing tubercle bacilli from 

 a growing culture with the fluids, taking out samples from time to time, 

 and sowing them on culture media. The values given may be regarded 

 as being good for most sporeless bacteria, the sensitiveness of which is 

 illustrated by this example. 



III. LETHAL VALUE FOR ANTHRAX SPORES. 

 From Paul n. Kronig (55). 



Substance. 

 Corrosive sublimate 



Concentration. Time (Temperature 18 C.)- 



7 % ( 16 litres) 12-14 minutes 



N itrate of silver 



99 



Sulphate of copper . 

 Sugar of lead . 

 Sulphuric acid 

 Caustic potash 

 Permanganate of potash 

 Bichromate of potash 



0-84% 

 0-42% 



0-2 % 



o-i % 



4-25% 

 0-08% 



1 6- % 



32-5 % 



4-9 % 



5-6 % 



3-95% 



( 32 

 ( 64 

 (128 

 (256 



( 4 

 (200 



( i 



( i 



( 



( 



( 



( 



2 

 I 



4 

 4 



24-30 



45-60 



60-80 



more than 120 minutes 



15-16 minutes 



not in ioi hours 



not in io days 



not in 7 ,, 



not in 30 hours 



1 8 hours 



40 minutes 



not in 4 days 



5 minutes 



2 



2 



not in 24 hours 

 120 minutes 



7-4 % 



Permang. of potash, 8 litres, plus 8 litres HC1 

 Chlorine water . . 0-22% ( 32 litres) 

 Bromine water . . 0-5 % ( 32 ) 



Carbolic acid . . 5 % 



Formaldehyde . . 5 % 



The lethal concentration for spores is determined in the following way. 

 A suspension of the spores in water is dried upon silk threads, pieces of 

 glass, or, better still, upon carefully-cleaned garnets, which are then laid in 

 the disinfectant. Specimens are taken out at intervals and sowed in nutri- 



G 2 



