PRELIMINARY REPORT ON SYNTHETIC MEDIA 145 



as HNO3. All the sources of nitrogen^ were added in proportion 

 to give one gram of their respective salts per liter. The mixture 

 of acids was then placed in a sterile flask plugged with cotton 

 and the flask connected with an automatic burette so that the 

 burette would fill by siphon. The silicate solution was placed 

 in another sterile cotton plugged flask and connected with another 

 automatic burette, so that it too would fill by siphon. Each 

 burette was allowed to fill and then stand several hours before 

 use, so as to sterilize completely the flasks and burettes. The 

 overflow cup of the burette was plugged with cotton, to prevent 

 contamination from the air during titration. When sterile, 

 5 cc. of the acid mixture was added to a sterile Petri dish, after 

 which there was added 5 cc. of the silicate solution. The plate 

 was then rotated to mix the two solutions thoroughly, and then 

 inoculated. If a non-acid compound was used as a source of 

 energy (say glucose) a sufficient amount of a sterile aqueous 

 solution, to give 10 grams per liter, was added at this point. 

 Numerous tests proved both the acid and silicate solutions to 

 be sterile in less than one hour. The resulting sihca medium 

 was neutral to phenolphthalein and set firmly in approximately 

 five minutes. When a compound other than an acid was used 

 as a source of energy it was added from a sterile aqueous solution 

 to the medium in the Petri dish just before inoculation. The 

 growth of organisms upon this sohd medium resulted generally 

 in quite typical colonies, although with a few organisms some- 

 what peculiar developments took place. 



The liquid media used had a concentration similar to the 

 above with the exception that H2Si03 was absent. It is pos- 

 sible that some organisms which failed to grow might have 

 grown in a lesser concentration. This was not determined 

 because the first consideration was to develop solid sj^nthetic 

 media, and a more dilute silicate solution would not solidify 

 soon enough; therefore the liquid media used as a check for 

 the solid media must necessarily be of the same concentration. 

 Parenthetically, it may be stated that the results of the liquid 



^ In future experiments, the availability of different salts of ammonia, nitrite, 

 nitrate and cyanid must be tested. . , 



