296 NON-NITROGENOUS NEUTRAL BODIES. 



acetic or citric acid, it becomes converted into glucose ; it ab- 

 sorbs large quantities of chlorine, hydrochloric acid, and ammo- 

 niacal gases. Nitric acid converts it into mucic acid with a little 

 oxalic, saccharic, and carbonic acid; with sulphuric acid and bichro- 

 mate of potash it yields not only formic acid but aldehyde. 



In contact with the caustic fixed alkalies it becomes converted 

 at 225 into oxalic acid ; boiled with dilute alkalies or oxide of lead 

 and water it becomes yellow or brown ; at 50 it yields several 

 compounds with oxide of lead. It reacts with sulphate of copper 

 and potash exactly in the same manner as glucose. It was for 

 a long time classed among the non- fermentable kinds of sugar, till 

 Schill* and Hessf almost simultaneously remarked that milk-sugar 

 only required a longer period in order to pass into a state of vinous 

 fermentation under the influence of yeast, sour dough, gelatin, or 

 albumen. H. RoseJ has confirmed SchilPs observations, that the 

 formation of dextrin must precede the vinous fermentation of the 

 milk-sugar, as indeed Payen had previously observed in reference to 

 the sugar of the dahlia, and Rose in reference to cane-sugar. Like 

 the other varieties of sugar, it can undergo lactic and butyric fer- 

 mentation when the necessary ferments are added to it. 



Composition. In its crystalline state milk-sugar has exactly the 

 same empirical formula as anhydrous glucose, so that it there- 

 fore contains equal equivalents of carbon, hydrogen, and oxygen. 

 But as, when warmed, it loses 11 '9$ of water, that is to say, 1 atom 

 of water to 5 atoms of carbon, its formula must either = C 5 H 4 O 4 or 

 a multiple of it. As milk-sugar cannot be combined with any body 

 in a definite proportion, its true atomic weight is unknown. Its 

 relation to nitric acid, with which, as we have already mentioned, 

 it yields mucic acid, shows that its constitution must in some 

 respects be different from that of the other fermentable sugars. 



Preparation. Milk-sugar is obtained on the large scale by 

 evaporating whey, and allowing the concentrated fluid to stand for 

 a long time in a cool place. The crystalline incrustations which 

 are then formed are purified by recrystallisation. Simon recom- 

 mends that the milk should be evaporated to ^th of its volume, and 

 that the casein should be precipitated by alcohol ; the filtered fluid 

 must be then further evaporated and treated with strong alcohol ; 

 the milk-sugar, which is precipitated with the water-extract, is then 



* Ann. d. Ch. u. Pharni. Bd. 31, S. 152. 

 t Pogg. Ann. Bd. 31, S. 194. 

 J Ibid. Bd. 52, S. 293. 



