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Exercise 24. Sulphate Reduction 
MATERIALS: 
100 cc. of sulphate medium 
3 tubes of sulphate agar 
One two ounce bottle with cork and string 
Old sewage 
SOLUTION FOR SULPHATE REDUCTION 
Di-basic potassium phosphate (K 2 IIP0 4 )__ 0.5 grams 
Sodium lactate (NaC 3 H 5 0 3 )_ 0.5 “ 
Ammonium sulphate (NH 4 ) a S0 4 )_ 2.0 “ 
Ferrous sulphate (FeS0 4 -f 7H 2 0)_ trace 
Tap water_ 1000.0 cc. 
1. Fill the bottle to the neck with the solution and inoculate it with one cc. 
of sewage. Stopper tightly and tie in the cork. 
2. Melt the tube of sulphate agar and cool it to 45 degrees G. Inoculate it 
with a few loopfuls of sewage. Mix well and solidify quickly in cold water. 
3. Incubate the cultures at 30° C. for one week. 
4. Examine the cultures and uncork the bottle. Describe the changes. 
5. (a) What causes the change in color? 
(b) What is the odor? 
(c) Under what kind of conditions as to oxygen did the change 
take place? 
( d ) What are the chemical changes? 
( e) What other process studied was similar to this? 
