EXAMINATION OF MILK. 11 



tallized from hot water. For this purpose put the milk- 

 sugar into a flask, dissolve it by heating with water (some 

 calcium phosphate always remains undissolved), add a little 

 bone-black to decolorize, and filter hot. Evaporate the solu- 

 tion to about 25 or 30 cc. (to sirupy consistency) on the water- 

 bath, let stand till next day, and place the crystals which 

 have separated on drying-paper. 



The milk-sugar forms hard, shining crystals, which dis- 

 solve in six parts of cold water, more readily in hot water, 

 and only slightly in alcohol. 



REACTIONS OF MILK-SUGAR. 



1. A small quantity heated on a crucible-cover or on 

 platinum-foil turns brown, gives off the odor of caramel, 

 carbonizes, and finally burns completely, leaving very little 

 ash. 



Milk-sugar like grape-sugar is oxidized in alkaline solu- 

 tion; a number of sugar reactions depend upon this property. 

 For the following reactions use a solution of 2 g. in 100 cc. 

 of water and another solution 10 times as dilute (10 ce. of the 

 solution diluted to 100 cc.). 



2. Trommer's Test. To a few cubic centimeters of the 

 solution add half the volume of caustic soda solution (of 

 about 1.17 sp. gr.), then add copper sulphate solution, drop 

 by drop, shaking the tube after the addition of each drop. 

 A deep-blue solution results, which on heating gives a pre- 

 cipitate of red cuprous oxide (or yellow cuprous hydroxide). 

 This property of dissolving cupric hydroxide in alkaline solu- 

 tion is common to milk-sugar, glucose, and to many other 

 organic substances, such as cane-sugar, glycerin, mannite, 

 and tartaric acid; but on warming these solutions no reduc- 

 tion takes place, except in the case of milk-sugar and glucose. 



3. Moore's Test. On the addition of an equal volume of 

 caustic soda solution of specific gravity 1.34 and heating to 



