84 LABORATORY WORK IN PHYSIOLOGICAL CHEMISTRY 



(a) Add an equal volume of ammonium molybdate and 

 warm to 70 C. What is the precipitate? Filter it off, dis- 

 solve in NH 4 OH and reprecipitate as ammonio-magnesium 

 phosphate. 



(6) Make a portion of the HN0 3 solution alkaline with 

 NH 4 OH and reacidify with acetic acid. Add a few c.c. of 

 ammonium oxalate. Examine the precipitate microscopic- 

 ally. 



LACTOSE. 



Lactose occurs only in milk, if the small amounts which 

 are occasionally present in the blood and urine of pregnant 

 women are disregarded. It is a disaccharide and breaks 

 down into a molecule of dextrose and one of galactose. It 

 undergoes yeast fermentation very slowly, but is easily 

 attacked by bacterium lactis, in which process lactic acid is 

 formed. With phenylhydrazin, lactose yields osazones, which 

 crystallize in needles and melt at 200 C. Lactose is soluble 

 in water, but does not dissolve in either alcohol or ether. 

 Its "solutions are dextrogyrate. 



Make use of the syrup derived from the last evaporation 

 in the milk-separation. 



(a) Try Fehling's, Moore's, and Ny lander's tests. 



(6) Apply the fermentation test. 



(c) Try the phenylhydrazin test (see p. 5). 



(d) To 5 c.c. of the lactose solution add sufficient freshly 

 prepared indigo-carmine solution to render the mixture 

 decidedly blue; then make it alkaline with dilute Na 2 C0 3 

 solution. Upon warming, the mixture becomes red, yellow, 

 and finally colorless. What do these changes indicate? 



