24 



PRACTICAL PHYSIOLOGY. 



[IIL 



(/".) It is precipitated from its saturated watery solution by 

 absolute alcohol. 



oo 



'^O 



FlO. 9.— Crystals of Lactose. FlO. 10.— Crystals of Phenyl-lactosazone, X 12c 



{g.) The phenyl-hydrazine test (fig. 10), it yields phenyl-lactosa 

 zone (C24H32N4O9). 



13. Preparation of Lactose (C,2H.>20„+HoO).— Acidulate milk with acetit 

 acid = precipitate of caseinogen and fat ; filter; boil filtrate to precipitate albumin, 

 and filter again ; evaporate the filtrate to small bulk ; set aside to crystallise. 



Milk-sugar is soluble in 6 parts of cold and 2^ parts of hot wat^r, but not in 

 alcohol. 



14. VIII. Cane-Sugax {G^^^^fi^^). 



{a.) Observe its crystalline form 



D(fig. 11) and sweet taste. 

 {h.) Its solutions do not reduce 

 ^ 4 FehUng's solution (many of the 



^^^^^y commercial sugars, however, con- 



K yi ^v tain sufficient reducing sugar to do 



(1 I 1 A rZW *'"')• 



XJ I J h '^1 I {(-.) Trommer's test : add excess 



^ ^ * 4'!/L.— -- - — l^ of caustic soda, and a drop of solu- 

 tion of copper sulphate (it gives a 

 clear blue fluid), and heat. With 

 a pure sugar there should be no reduction. 



{(1.) Pour strong sulphuric acid on cane-sugar in a beaker, add 

 a few drops of water ; the whole mass is quickly charred, 

 (e.) Heat the solution with caustic soda = it darkens slowly. 

 (/.) It is practically insoluble in absolute alcohol, but its solu- 

 bihty greatly increases with the dilution of tlie alcohol. 



((J.) Inversion of Cane-Sugar. — Boil a strong solution of aane- 

 sugar in a flask with one-tenth of its volume of strong hydro- 

 chloric acid. After prolonged boiling the cane-sugar is "inverted," 



Fia. II.— Crystals of Cane-sugar. 



