THE PREPARATION OF VINEGAR 223 



temperature. This species is further easily distinguished from the 

 fact that the mucilage is stained blue by a solution of iodine in 

 potassium iodide. 



Bacterium Kiitzingianum Hansen. This species, like Bacterium 

 Pastorianum, forms a dry film on the surface of " doppel " beer, but as 

 this film rises high above the liquid along the sides of the flask, the 

 species is readily distinguished from the other acetic-acid bacteria. 

 The film consists of small rod-bacteria (Fig. 125), and only rarely 

 forms threads. As in Bacterium Pastorianum, the mucilage of the 

 film is stained by a solution of iodine in potassium iodide. Other 

 bacteria capable of forming vinegar from alcohol are Bacterium xylinum, 

 Bacterium vermiforme, Bacterium acetigenum, Termobacterium aceti, 

 and Termobacterium lutescens. The exact relation of these species to 

 the production of vinegar has not been extensively studied. Beijerinck 

 mentions Bacterium aceti as the organism concerned in the quick- 

 vinegar manufacture, but it seems to be still doubtful whether this 

 species is identical with the Bacterium aceti which we have described 

 above. Bacterium xylirium and Bacterium acetigenum are known to 

 occur in the acetifiers of the quick-vinegar process. 



