CHEMICAL CHANGES 



109 



[bases present, their salts being afterwards further broken down 

 iby such fermentations as are given in the annexed table.^ 



Table of Fermentation of Organic Acids. 



iFor simplicity, the sodium salts are taken, though the lime salts are rather more 



fermentable.) 



LSalt Fermented. 



[Formate 



Acetate 



Lactate 

 (Undergoes 



I four different 

 fermenta- 

 Malate 

 (Different fer- 

 mentations. ) 



Cause of Fermentation. 



' Bacteria from sewage 

 slime." 



•' Bacteria from sewage 

 slime." 



'Thin bacillus "(Fitz). 

 " Other species of 

 bacteria ; short aero- 

 bic butyric bacteria " 

 (Fitz). 



Products. 



Acid sodium carbonate, NaHCOg, car- 

 bonic acid and hydrogen. 



NaHCOg. CO2, and methane, CH4. 



1. Propionic acid, and as by-products 



acetic and succinic acids and alcohol. 



2. Propionic and valeric acid. 



3. Butyric and propionic acid. 



4. Butyric acid and hydrogen. 



Bacteria not described. 



" Thin bacilli." 

 B. lactis aerogenes (O. 



Emmerling). 



Chief product, propionic acid ; by- 

 product, acetic acid. 



Chief product, succinic acid ; by- 

 product, acetic acid. 



Butyric acid and hydrogen. 



Lactic acid and CO... 



Tartrate 



Citrate 





Different species of 

 bacteria. 



1. Chief product, propionic acid; by- 



product, acetic acid. 



2. Butyric acid. 



3. Chief product, an acetate; by-pro- 



ducts, alcohol, butyric and succinic 

 acids. 



Small, thin bacilli.' 



Acetic acid in large quantities, with 

 small quantities of alcohol and suc- 

 cinic acid. 



Micrococci ; medium- 

 sized bacilli. 



I. An acetate, with small quantities of 



succinic acid and alcohol. 

 2 Formic acid, with some methyl alcohol 



and acetic acid. 



Under active microbic fermentation all eventually pass into 

 CO2 and H, or CH4. The COg is partly free and partly as 

 bicarbonate of the base. Acetic acid is generally the penulti- 

 mate product, therefore the common production of methane. 



^ Herfeldt, Centr. f. Bakt, February, 1895 ; journal of the Society of Chemical 

 Industry, May, 1895. 



