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efficiency of a disinfectant has become widely adopted. The principle of this method is that the strength of a particular disinfectant is expressed in multiples of pure phenol, performing the same work. In this way a ratio is obtained which is now well known as the " Carbolic Acid Co-efficiency of the Disinfectant."
The following disinfecting fluids were submitted to me by the Secretary of the Sanitary Board for examination as to their co-efficiency :--
1. Carbolated Creasote.
2. Jeye's Fluid.
3. Cyllin [2 samples].
3. Blackhead's Disinfecting Fluid, [2 samples].
Rideal and Walker's method of estimating the co-efficiency was used. The micro- organisms used for the different tests were :-
1. B. Typhosus.
2. B. Coli Commune.
3. B. l'estis.
These organisms were grown in broth culture for at least 24 hours at a temperature of 37° C. and then mixed with varying proportions of the particular disinfectant, a standard solution of carbolic acid being used in addition. After the culture had been exposed to the action of the disinfectant for a definite time, sub-cultivation was made from the mixture in order to determine whether the particular strength of the disinfectant had been efficient as a germicide. It is quite unnecessary in the present Report to give in detail a number of tables indicating the method by which the carbolic acid co-efficient of each disinfectant towards each particular micro-organism was obtained. One example will suffice in order to demonstrate my method.
Carbolated Creusote.
Table I.
B. Typhosus, 24 Hours Broth Culture at 37° C.
Sample.
Dilution.
1 in 100.
1 in 200.
Carbolated Creasote,
1 in 300.
1 in 500.
Carbolic Acid,
I in 100.
Time limit of Exposure,
2
X
X
X
X
Minutes.
сл
5
7
10
X
X
X
Sub-cultures.
Period of Incubation.
Temperature
48 hours.
37°C.
X
+
X
"1
17
"
"
X
X
*
Carbolic Acid Co-officient-3.
Table II.
B. Coli, 24 Hours Broth Culture, at 37°C.
Time limit of Exposure.
Sample.
Dilution.
Sub-cultures.
*
Minutes.
Period of Incubation.
Temperature.
10
I in 100.
X
Carbolated Creasote,
1 in 200,
X
X
1 in 400.
X
Carbolic Acid,
1 in 100.
X
Carbolic Acid Co-efficient=2.
:
48 hours.
37°C.
33
37
35
"
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