2ig 



That the ferric reaction is in fact caused by pyruvic acid is corroborated by 

 the following observations. 



The conversion of the malate can very well occur in a strongly aerated culture 

 liquid, for instance in an Erlenmeyer- flask containing a thin layer of: 100 

 tapwater, 2 calciummalate, o.i ammonium sulfate, 0.02 potassium phosphate, with 

 or without ferric citrate as an indicator. By infection with B. ftuorescens and when 

 cultivated at 20 to 25 C., after a few days the pyruvic acid can be destilled with 

 sulfuric acid and be recognised in the destillate, not only by the odour and ferric 

 salts, but also by the two following reactions: with the sulfite of hydrazin a charac- 

 teristic penylhydrazon results, and with ammoniacal nitroprussidsodium a violet 

 colouring is obtained, which by acetic acid passes into blue, with potash into red x ). 



Indirectly the correctness of our diagnose was proved by the fact that as well 

 alanin as asparaginic acid with the fluorescent bacteria, and besides with B. levans 

 and B. viscosus, produce the iron reaction, so that also from these substances, in 

 accordance with our expectation, pyruvic acid results. 



On the other hand, this acid cannot be obtained from asparagin, aminopropionic 

 acid, and glycerin, nor, as has already been noted, from maleinic acid. 



') Rosenthaler, Der Nachweis organischer Verbindungen. pag. 300, 1914. 



