CULTURAL CHARACTERS OF BACTERIA 



39 



the influence of a solution of its zinc salt upon the polarized ray. 

 The residue of zinc salt is accordingly dissolved in only enough 

 water to fill the shorter tube of the polariscope, and its action 

 upon the polarized ray determined in the usual manner. 



The system of analysis for the organic acids is given in outline 

 in the following diagram: 



CULTURE MADE IN A ONE-LITRE FLASK CONTAINING 500 cc. OF 2 PER CENT 

 GLUCOSE BOUILLON AND 10 GR. OF STERILE CaCO 3 . 



Filter and wash with cold water. 



Distillate, volatile acids. 

 Acetic, 

 Formic, 

 Propionic, 

 Butyric. 



Titrate a portion. 

 Remainder saturate with baryta 



water to alkaline reaction. 

 Evaporate to dryness. and add 



10 parts of absolute alcohol. 

 Let stand, with frequent stirring, 

 for i to 2 hours. Filter and 

 wash with alcohol. 



Residue, 

 lactic, oxalic, succinic, 



glycocholic acids. 

 Evaporate to syrupy consist- 

 ency and extract with ether. 

 Evaporate off ether to syrupy 

 consistency; add water, and 

 boil with ZnO. Filter. 



I 



Filtrate, zinc lactate, 

 nearly pure. Evap- 

 orate to dryness. 

 Take up in hot 

 water = solution of 

 pure zinc lactate. 



Residue, 



zinc 

 oxalate 



and 

 succinate. 



Residue, barium for- 

 mate and acetate. 

 Evaporate off all al- 

 cohol, and test for 

 formic and acetic 

 acids. 



Filtrate, mainly barium propionate 

 and butyrate, and a little formate 

 and acetate. Evaporate to dry- 

 ness ; dissolve in 150 cc. water. 

 Saturate with CaCl 2 and distil 

 off pure butyric acid. 



