20 ELEMENTARY BACTERIOLOGY LABORATORY EXERCISES 
N/20 HCl if the original reaction is more alkaline than pH 7.0) using brom- 
thymol blue as indicator. From the amount of N/20 NaOH (or N/20 HCl) nec- 
essary to adjust 5 c.c. to pH 7.0, calculate how much N/l NaOH (or N/| HCl) 
would be required to adjust one liter of the same medium to a reaction of pH 7.0. 
By the same methods adjust 5 c.c. portions of different media to a reaction of 
pH 5.2, using methyl red as indicator, and calculate the required amounts of 
N/1 NaOH or N/I HCI to adjust one liter amounts of the same media to a reac- 
tion of pH 5.2. 
If end points of pH 9.0, pH 8.0, pH 7.4, pH 6.2, and pH 4.2 were desired, 
which indicators would you select? 
EXERCISE 32 
NUTRIENT BROTH OR BOUILLON 
Prepare one liter of nutrient broth using the following formula: 
0.3% beef extract 
0.5% peptone 
Distilled water 
Reaction, pH 7.0 
Procedure 
(1) Mix the above ingredients and steam for about 10 minutes to dis- 
solve the ingredients. : 
(2) Determine the hydrogen ion concentration and adjust to the desired 
reaction. 
(3) Heat in the autoclave under 15 pounds pressure for 10 minutes in order 
to precipitate heat coagulable substances, 
(4) Filter through paper. 
(5) Measure and restore any loss from evaporation by the addition of dis- 
tilled water. 
(6) Distribute in the desired containers, and sterilize in the autoclave at 
15 pounds pressure for 30 minutes. 
