156 ATLAS OF BACTERIOLOGY. 



is based on the fact that hydrogen, when mixed with 

 oxygen and passed over glowing palladium asbestos, 

 is converted into. water and accordingly disappears; 

 carburetted hydrogen is changed into carbonic acid 

 in a glowing platinum capillary tube, and is measured 

 as such, and the remainder is nitrogen. With some 

 practice the examination is easy and accurate. 



14. Production of Acids from Alcohols and other 

 Organic Acids. 



It has long been known that bacterium aceti or its 

 nearest allies convert weak solutions of ethyl alcohol 

 into acetic acid, at the same time using up a large 

 amount of oxygen : 



CH 3 + O 2 = CH 3 + H 2 

 [ 2 OH COOH 



VX.M--*.; 



CH S 



Higher alcohols, such as glycerin, dulcite, and 

 mannite, are also converted into acids; glycerin as 

 generally as sugar (v. Sommaruga: Z. H., XV., 291). 



Finally, numerous observations have been made on 

 the conversion, by bacteria, of acids of the fatty 

 series (or their salts) into other fatty acids, but unfor- 

 tunately the majority were not made with pure cul- 

 tures which meet the modern requirements. Lactate, 

 mallate, citrate, and gly cerate of lime were usually 

 employed as the material and almost always acid 

 mixtures were obtained as the result of the bacterial ac- 

 tivity. Among these butyric, propionic, valerianic, 

 and acetic acids play the principal part; succinic 

 acid and ethyl alcohol are often found ; formic acid is 

 rarer. Among the gases carbonic acid and hydrogen 

 are especially prominent. 



