146 C. J. T. DORYLAND 



and solid media did not always agree. The acetic ammonium 

 medium will give an approximate idea of the composition and 

 concentration. 



Acetic-ammonia-silicate medium 



HsSiOs 17 . 1366 



NaCl 1.1620 



Na2S04 2.8209 



NaCsHsOz 1 .6343 



Na2H PO4 4. 2330 



K CI 3 . 2954 



K,S04 7.7024 



K C2H3O2 4.3357 



K2H PO4 11. 5500 



MgS04 0.5000 



CaO 0.0100 



Fe2(S04)3 0.0100 



MnSO 0.0100 



(NH4)2S04 1.0000 



Water double dist 1000.0000 



The acetic ammonia solution agrees with the above, except- 

 ing that it does not contain the H2Si03, It may be made as 

 follows: Make a solution of KOH and one of NaOH so that 1 cc. 

 of each alkali will just neutralize 1 cc. of one of the acids which 

 was standardized against the sihcate solution. The KOH 

 and NaOH solutions are then mixed in such proportions that 

 when the mixture is brought in contact with the acid mixture 

 the resulting sodium and potassium chlorides, sulphates, phos- 

 phates and acetates are present in quantities inversely propor- 

 tional to their osmotic action. The acids may be prepared 

 as previously described. The alkah mixture and the acid mix- 

 ture may be placed in their respective bottles and connected 

 by siphon with automatic burettes. Allow the burettes to fill 

 as with the silicate medium and when sterile equal quantities 

 of the alkali mixture and of the acid mixture may be run from 

 the burettes in a suitable vessel. 



It must be borne in mind that when glucose or an alcohol, 

 or any other non-acid compound is used as a source of energy 

 the proportion of each of the remaining salts increases. Like- 

 wise, the relative proportion changes when another acid, such 

 as formic or lactic, is used in place of acetic acid. This fluctua- 



