CULTURE MEDIA 29 



For certain organisms it is advisable to add an excess of 

 CaCOs. 



Medium 68 



Sulphur-phosphate Medium^ 



Ammonium sulphate ((NH4)2S04) 0.2 gm. 



Monopotassium phosphate (KH2PO4) 3.0 gm. 



Magnesium sulphate (MgS04-7H20) 0.5 gm. 



Calcium chloride (CaCU-GHsO) . 25 gm. 



Ferrous sulphate (FeS04-7H20) trace 



Sulphur, powdered 10 . gm. 



Distilled water 1,000 . cc. 



1 Waksman, S. a., Soil Set., 13: 329, 1922. 



The sulphur is weighed out into the individual containers, 

 usually 1-gram portions into 250-cubic centimeter Erlenmeyer 

 flasks, and 100-cubic centimeter portions of the liquid medium 

 added. The reaction of the medium is about pH 4.0. The 

 flasks are sterilized in flowing steam on 3 consecutive days. 



Medium 69 



SODIUM-THIOSULPHATE AgAR2 



Agar 20 . gm. 



Sodium thiosulphate (Na2Si03-5H20) 5.0 gm. 



Ammonium chloride (NH4CI) 0.1 gm. 



Calcium chloride (CaClo-GHzO) . 25 gm. 



Magnesium chloride (MgCl2-6H20) 0.1 gm. 



Monopotassium phosphate (KH2PO4) 3.0 gm. 



Distilled water 1,000 . cc. 



2 Waksman, S. A., /. Bad., 7: 605, 1922. 



The medium is prepared as usual and sterilized at 15 pounds' 

 pressure for 15 minutes. 



Medium 70 

 Solution for the Reduction of Hydrogen Sulphide 



Ammonium sulphate ((NH4)2S04) 1.5 gm. 



Potassium chloride (KCl) . 05 gm. 



Magnesium sulphate (MgS04-7H20) 0.05 gm. 



Dipotassium phosphate (K2HPO4) . 05 gm. 



Calcium nitrate (Ca(N03)2) 0.01 gm. 



Calcium carbonate (CaCOs) 10 . gm. 



