PRACTICAL PHYSIOLOGY. 



[III. 



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

 absolute alcohol. 



FIG. 9. Crystals of Lactose. 



FIG. io. Crystals of Phenyl-iactosazone, x 120 



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

 zone (C 24 H 32 N 4 9 ). 



13. Preparation of Lactose (C| 2 Ho20 n +HoO). Acidulate milk with acetic 

 acid = precipitate of caseinogen and i'atf; filter; boil filtrate to precipitate albumin, 

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



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

 alcohol. 



14. VIII. Cane-Sugar (C 12 H 22 O n ). 



(a.) Observe its crystalline form 

 (fig. n) and sweet taste. 



(/?.) Its solutions do not reduce 

 Fehling's solution (many of the 

 commercial sugars, however, con- 

 tain sufficient reducing sugar to do 

 this). 



(c.) Trommer's test : add excess 

 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. 



(d.) 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- 

 bility greatly increases with the dilution of the alcohol. 



(//.) Inversion of Cane-Sugar. Boil a strong solution of cane- 

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

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



I'IG. ii. Crystals of Cane-sugar. 



