LACTOSE. 655 



Lactose responds to the reactions of glucose, such as MOORE'S,* 

 TROMMER'S and RUBNER'S, and the bismuth test. It also reduces mer- 

 curic oxide in alkaline solutions. After warming with phenylhydrazine 

 acetate it gives on cooling a yellow crystalline precipitate of- phenyl 

 lactosazone, C24H32N 4 Og. It differs from cane-sugar by giving positive 

 reactions with MOORE'S or TROMMER'S and the bismuth test, and also in 

 that it does not darken when heated to 100 C. with anhydrous oxalic 

 acid. It differs from glucose and maltose by its solubility and crystalline 

 form, but especially, by its not fermenting with yeast, and by yielding 

 mucic acid with nitric acid. 



The osazone obtained with phenylhydrazine acetate, which melts at 

 200 C., differs from the other osazOnes by being inactive when 0.2 gram 

 is dissolved in 4 cc. of pyridine and 6 cc. of absolute alcohol and viewed 

 through a layer 10 centimeters long (NEUBERG 2 ). 



For the preparation of milk-sugar we make use of the by-product 

 in the preparation of cheese, the sweet whey. The protein is removed 

 by coagulation with heat, and the filtrate evaporated to a syrup. The 

 crystals which separate after a certain time are recrystallized from water 

 after decolorizing with animal charcoal. A pure preparation may be 

 obtained from the commercial milk-sugar by repeated recrystallization. 

 The quantitative estimation of milk-sugar may be performed either by 

 the polaristrobometer or by means of titration with FEHLING'S solution. 

 Ten cc. of FEHLING'S solution are reduced by 0.0676 gram of milk-sugar 

 in 0.5-1.5 per cent solution after boiling for six minutes. (In regard to 

 FEHLING'S solution and the titration of sugar see larger hand-books.) 



From the non-correspondence between the quantity of sugar in the 

 milk as determined by polarization and gravimetrically, when the polar- 

 ization results are always higher, SEBELIEN S has concluded that the 

 milk must contain a second reducing substance which polarizes stronger 

 than lactose. This substance is probably a pentose and occurs to a very 

 slight extent in ordinary milk, 0.25-0.35 p. m. (SEBELIEN and SUNDE), 

 and more in colostrum, 0.5 p. m. 



RITTHAUSEN found another carbohydrate in milk which is soluble in water, 

 non-crystallizable, which has a faint reducing action, and which yields, on boiling 

 with an acid, a body having a greater reducing power. BECHAMP 4 considers 

 this as dextrin. 



A The well-known beautiful red color, which milk produces after the addition of 

 alkali, at the room temperature and to which attention has been called recently by 

 Gautier, Morel, and Monod (Compt. rend. soc. biol., 60 and 62), and Kriiger (Zeitschr. 

 f. Physiol. Chem., 50) is a Moore's reaction modified by the presence of protein and 

 perhaps also other milk constituents. 



2 Ber. d. d. Chem. Gesellsch., 32. 



'Sebelien, Hammarsten's Festschrift, 1906; with Sunde, Zeitschr. f. angew. 

 Chem., 21. 



4 Ritthausen, Journ. f. prakt. Chem. (N. F.), 15; Bechamp, Bull. Soc. Chim. (3), 6. 



