NH4Cl 0.1 g KH2PO4 3.0 g MgCl.6H2O 0.1 g CaCl2 0.1 g Na2S2O3.5H2O 5.0 g Purified agar 20.0 g Distilled water 1.0 L Preparation: ? Dissolve all except the agar in distilled water and adjust the pH to 4.2. ? Add the agar and steam to dissolve. ? Autoclave at 121oC for 15 minutes.