40 PHYSIOLOGICAL CHEMISTRY 



ISO-MALTOSE, C^H^On 



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

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

 of hydrochloric acid upon glucose. 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 characteristic. Iso-maltose 

 is very soluble and reduces the oxides of bismuth and copper in alkaline 

 solution. Pure iso-maltose is probably only slightly fermentable. 



LACTOSE, Ci2H 22 Oii 



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 glucose and one molecule 

 of galactose. 



In the souring of milk the bacterium lactis and certain other micro- 

 organisms bring about lactic acid fermentation by transforming the lac- 

 tose of the milk into lactic acid, 



H OH 



I I 

 H C C COOH, 



I I 

 H H 



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

 the result of the action of putrefactive bacteria. In the preparation 

 of kephyr and koumyss the lactose of the milk undergoes alcoholic 

 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. 



EXPERIMENTS ON LACTOSE 



1-6. Repeat Solubility, Fehling's, Phenylhydrazine, Barfoed's, Nylander's 

 and Fermentation tests as given under Glucose, pages 21-31. 



7. Mucic Acid Test. Treat 100 c.c. of the solution containing lactose with 

 20 c.c. of concentrated nitric acid (sp. gr. 1.4) and evaporate the mixture in a 

 broad, shallow glass vessel on a boiling water-bath, until the volume of the mix- 

 ture has been reduced to about 20 c.c. At this point the fluid should be clear, 

 and a fine white precipitate of mucic acid should form. 



