66 LABORATORY BACTERIOLOGY. 



EXEKCISE LIIl. 



THE FORMATION OF ORGANIC ACIDS. 



1. Measure off four 100 cc. portions of "synthetic" solu- 

 tion in 150 cc. Erlenmeyer flasks. Add to each portion 1 

 drop of a 1% solution of Fe^Cle and 2 or 3 drops of a 1% 

 fiolution of CaClg. 



2. Plug and sterilize in the autoclave. 



3. Prepare 400 cc. of the similarly modified ■ "synthetic" 

 solution using KNOa instead of peptone. 



4. Measure ofl: four 100 cc. portions of this solution in 

 150 cc. Erlenmeyers; plug and sterilize as usual. 



5. Arrange thus: 



1 & 2 — "Synthetic" solution — Az. vinelandii. 



3 & 4 — "Synthetic" solution — Az. chroococcum. 



5 & 6 — "Synthetic" solution using KNO, — B. myeoides. 



7 & 8 — "Synthetic" solution using KNOj — B. subtilis. 



6. Inoculate with 1 cc. of vigorous cultures of the above 

 named organisms. 



7. Incubate 10-14 days at 20° C. 



8. Test qualitatively for acetic, butyric, and lactic acids. 



