ontrol at the 2-1/2-minute
contact period by the figure representing the percentage strength of the
weakest lethal dilution of the x-disinfectant at the same period. The
quotient = phenol coefficient at 2-1/2 minutes.

(b) Similarly obtain the phenol coefficient at 30 minutes contact
period.

(c) Record the mean of the two coefficients obtained in (a) and (b) as
the _mean phenol coefficient_, or simply as the ~Phenol Coefficient~.

The details of the Final Test of an actual determination are set out in
the accompanying table.

TABLE 27

Organism employed, B. Coli Communis.

Culture Medium, Nutrient Agar (+10). Age, 24 hrs.
Temp. of Incubation, 37 deg. C.

Quantities used { Culture } Emulsion 0.1 c.c. + 5 c.c. Germicide.
{ Emulsion }

Room Temperature during Experiments, 17 deg. C.

Germicide Strength Time of exposure Incubation
2-1/2 5 10 15 20 25 30 35 Time Temp.
1 Germicide-x 4% -- -- -- -- -- -- -- -- 7 days. 37 deg. C.
2 Germicide-x 3% 48 -- -- -- -- -- -- -- 7 days. 37 deg. C.
3 Germicide-x 2% 24 24 24 24 48 72 7 days. 37 deg. C.
4 Germicide-x 1% 24 24 24 24 72 24 72 7 days. 37 deg. C.
5 Germicide-x 0.5% 24 24 24 24 24 24 24 24 24 hours. 37 deg. C.

1 Phenol 1.10% -- -- -- -- -- -- -- -- 7 days. 37 deg. C.
2 Phenol 1.00% 24 7 days. 37 deg. C.
3 Phenol 0.75% 24 24 24 24 48 7 days. 37 deg. C.
4 Phenol 0.70% 24 24 24 24 24 72 7 days. 37 deg. C.
5 Phenol 0.65% 24 24 24 24 24 48 24 24 2 days. 37 deg. C.

((1.10/4.00) + (0.7/2.0)) 0.27 + 0.35 .62
Phenol Coefficient = ------------------------ = ----------- = --- = 0.31
2 2 2

APPENDIX.

METRIC AND IMPERIAL SYSTEMS OF WEIGHTS AND MEASURES.

The initial unit of the metric system is the Metre (_m._) or unit of
length, representing one-fourth-millionth part of the circumference of
the earth round the poles.

The unit of mass is the Gramme (_g._), and represents the weight of one
cubic centimetre of water at its maximum density (viz. 4 deg. C. and
760 mm. mercury pressure).

The unit of the measure of capacity is the Litre (_l._), and represents
the volume of a kilogramme of distill