174 STERILIZATION AND DISINFECTION 
the egg albumen test solution, in order to find that dilution of the disin- 
fectant which fails to show any opacity. We will suppose that the 
1/1000 sub-stock solution shows very marked opacity or precipitation, 
then the 1/10,000 solution might be tried, which may also show quite 
marked opacity, then the 1/100,000 may be tried. If this gives nega- 
tive results then we know that the phenol standard lies between 
1/10,000 and 1/100,000, with the probabilities that it is nearer 1/10,000. 
TABLE XXI 
PLAN FOR TEN DILUTIONS AT THIRTY-SECOND INTERVALS 
InocuLaTe | 5-Min Trst |10-Min Trst |15-Min Test 20-Min Trst 
Seeding Dilution. To -_— oo a a ns 
Man | Sec ; Min | Sec Min | Sec | Min | Sec | Min ! See 
1 1: 80 00 ; 00 5 00 | 10 | 00 15 |; 00 | 20 | 00 
2 1: 90 00 | 380 5 30 10 | 30 15 | 30 | 20 | 30 
3 1 : 100 1 ; 00 6 00 | il 00 |; 16 | 00 | 21 | 00 
4 1: 110 1 | 30 6 30 11 30 16 | 30 | 21 | 30 
5 1 : 120 | 2 | 00 7 00 12 | 00 17 | 00 | 22 | 00 
6 1 : 360 2 | 80 7 30 12 30 17 | 80 | 22 | 380 
7 1 : 400 3 | 00 8 00 | 138 | 00 | 18 | 00 | 23 | 00 
8 1 : 440 3 | 30 8 30 | 13 | 30 | 18 | 30 | 238 | 30 
9 1 : 480 4 |; 00 9 00 14 | 00 19 | 00 | 24 | 00 
10 1 : 520 | 4 | 30 9 30 | 14 | 30 | 19 | 80 | 24 | 30 
(c) Concluding Testing. Going back to the 1/10,000 dilution make 
ten sub-dilutions, increasing the dilutions by a difference of 1000 by 
simply adding the required parts of distilled water, using small quan- 
tities, thus: 
10 parts of 1/10,000+1 part water =1/11,000. 
10 parts of 1/10,000+2 parts water =1/12,000. 
10 parts of 1/10,000-+3 parts water = 1/13,000, etc. 
Any other quantity proportions may be used, however, as 10, 15 
20, etc., parts of the sub-stock solution with the required parts of dis- 
tilled water. If the 1/1000 sub-stock solution is to be used then the 
dilutions should be increased by 100 as follows: 
10+1=1/1100 
10-+2= 1/1200 
10-+3 = 1/1300 
10-++-4=1/1400; 
