MILK-SUGAR. 297 



rinsed with a little water, dissolved in pure water, and left to 

 spontaneous evaporation. 



According to Haidlen* the milk should be boiled with th its 

 weight of pulverised gypsum, which coagulates the casein ; the 

 filtered fluid is then to be evaporated to dryness, and after the fat 

 has been removed by ether, the milk-sugar may be extracted from the 

 residue by boiling alcohol, which yields it in a state of perfect purity. 



Tests. If it be shown by Trommer's test that some kind of 

 sugar is contained in the alcoholic extract of an animal fluid, we 

 may readily distinguish milk-sugar from other kinds of sugar (if 

 we have a sufficient amount of material to examine,) by its difficult 

 solubility in alcohol, by the slowness with which it ferments in the 

 presence of yeast, and by its property of yielding the insoluble 

 mucic acid when boiled with nitric acid. It may be estimated 

 quantitatively with tolerable accuracy by Haidlen's method given 

 above ; but when extreme accuracy is required we must use Barres- 

 wil's or Fehling's test-fluid, in the manner described for grape-sugar 

 (see p. 287) 5 Poggiale has in this way determined the sugar in cow's 

 milk by a test-fluid (consisting of 10 parts of crystallised sulphate 

 of copper, 10 of bitartrate of potash, 30 of caustic potash, and 200 

 of distilled water), but his results were obviously in excess ; for 

 although he attempted to remove the casein previously with acetic 

 acid, a portion of this substance must have remained in solution 

 and cooperated with the sugar in decomposing the oxide of copper- 

 A better method of proceeding is to remove the casein by boiling the 

 milk with sulphate of magnesia or chloride of calcium, precipitating 

 any excess of the earth from the filtered fluid with potash, and then 

 applying Fehling's test-fluid ; while perhaps the best is to proceed 

 according to Haidlen's plan, and then to apply Fehling's method to 

 determine the quantity of milk-sugar in the alcoholic extract. 



Physiological Relations. 



Occurrence. This substance appears to be an integral consti- 

 tuent of the milk of all mammalia. In woman's milk its amount 

 ranges from 3'2 to 6'24% (Fr. Simon,f Haidlen,J Clemm,) ; in 

 cows' milk it is stated to average from 3 -4 to 4'3&; but by an im- 

 proved method of analysis I have always found rather a larger 

 amount of sugar in good cows' milk; but the average (= 5'28g) 



* Ann. d. Ch. u. Pharm. Bd. 45, S. 275. 

 t Frauenmilch. S. 35. 

 $ Ann. d. Ch. u. Pharm. Bd. 45, S. 275. 

 Handworterbuch d. Phys. Bd. 2, S. 464. 



