4O PHYSIOLOGICAL CHEMISTRY. 



EXPERIMENTS ON MALTOSE. 



i ii. Repeat these experiments as given under Dextrose, pages 



23-31- 



ISO-MALTOSE, C^H^On- 



Iso-maltose, an isomeric form of maltose, is formed, along with 

 maltose, by the action of diastase upon starch paste, and also by 

 the action of hydrochloric acid upon dextrose. It also occurs with 

 maltose as one of the products of salivary digestion. It is dextro- 

 rotatory and with phenylhydrazine gives an osazone which is char- 

 acteristic. Iso-maltose is very soluble and reduces the oxides of 

 bismuth and copper in alkaline solution. Pure iso-maltose is prob- 

 ably only slightly fermentable. 



LACTOSE, C 12 H 22 O n . 



Lactose or milk sugar occurs ordinarily only in milk, but has 

 often been found in the urine of women during pregnancy and 

 lactation. It may also occur in the urine of normal persons after 

 the ingestion of unusually large amounts of lactose in the food. 

 It has a strong reducing power, is dextro-rotatory and forms an 

 osazone with phenylhydrazine. Upon hydrolysis lactose yields one 

 molecule of dextrose and one molecule of galactose. 



In the souring of milk the bacterium lactis and certain other 

 micro-organisms bring about lactic acid fermentation by transform- 

 ing the lactose of the milk into lactic acid, 



H OH 

 H-i-i- 

 I 



COOH, 



and alcohol. This same reaction may occur in the alimentary canal 

 as the result of the action of putrefactive bacteria. In the prepara- 

 tion of kephyr and koumyss the lactose of the milk undergoes alco- 

 holic fermentation, through the action of ferments other than yeast, 

 and at the same time lactic acid is produced. Lactose and galactose 

 yield mucic acid on oxidation with nitric acid. This fact is made 

 use of in urine analysis to facilitate the differentiation of these 

 sugars from other reducing sugars. 



Lactose is not fermentable by pure yeast. 



