DISINFECTANTS 489 



probably be available to enable a second trial test to 

 be planned which will give the required information. 



Final Test. 



c. Determination of Phenol Coefficient. 



X-Disinfectant. This comprises two distinct tests, 

 one of the Germicide-x, the other of the standard 

 phenol. 



1 . Arrange five test-tubes clearly marked in the lower 

 tier of the rack. 



2. Pipette into each 5 c.c. respectively of the five 

 percentage solutions of x-disinfectant which the trial 

 run has already shown will include those affording 

 lethal values at 2^ and 30 minutes. 



3. Arrange 20 tubes of bile salt broth in the upper tier 

 of the test-tube rack in two rows, those in the front 

 row numbered consecutively from left to right i-io, 

 those in the back row 11-20. 



4. Arrange further 20 tubes of bile salt broth num- 

 bered 2 1-40 in two rows in a second smaller rack which 

 can be stood on the upper tier of the rack as soon as 

 the first 20 tubes have been inoculated. 



5. Place a square wire basket of about 50 tube 

 capacity close to the left of the test-tube rack, for the 

 reception of the inoculated tubes. 



6. Adjust a sterile i c.c. pipette in the mouth of each 

 of the tubes, A, B, C, D and E, by means of a washer, as 

 previously described. 



7. Set the electric signal clock to ring for the com- 

 mencement of the experiment and subsequently at 

 2j, 5, 10, 15, 20, 25, 30 and 35 minutes. 



8. Complete precisely as indicated in Trial Runs, 

 steps 9-19. 



Control Phenol. 



Immediately the subculture tube from the 3o-minute 

 contact period have been inoculated, carry out a pre- 



