and^^^^^K' when ^ma cow's milk. The ordinary souring 

 of milSHB^lto the formation of lactic acid from the lactose 

 by m^fcojjjg-anisms. Lactose must be transformed into dex- 

 tro*before it can be assimilated! If injected into the veins 

 it appears in the urine. Use a 2 9^ solution of lactose. 



76. Test a portion of the solution with Barfoed's rea- 

 gent. Compare with the similar test for dextrose. 



77. Heat a portion of the solution carefully with sul- 

 phuric acid, — it chars slowly. (See 67). 



78. Add to another portion excess of caustic potash and 

 a few drops of copper sulphate solution and heat, — a yellow 

 or red precipitate (like glucose). 



79. Test another portion with Fehling's solution, — there 

 is a reduction like glucose, but its reducing power is not so 

 great as glucose. It requites 10 parts of lactose to reduce the 

 amount of Fehling's solution that will be reduced by 7 of 

 glucose. 



80. Apply the phenylhydrazine test and compare care- 

 fully the form of the crystals with those obtained in the 

 dextrose solution. 



81; Sucrose. Cane sugar, (C^Jl^fl„). Cane sugar is 

 found in plants, not in the animal kingdom. It has no reduc- 

 ing power, but is decomposed by heating with acid into a 

 molecule of dextrose and one of fructose (fruit sugar). Make 

 a 2% solution of cane sugar. 



82. A portion of the solution should not reduce Fehling's ^ 

 solution. (Many of the. commercial sugars, however, contain lJty\ 

 sufl&cient reducing sugar to do this.) ^ . 



83. Trommer's test. Add excess of caustic potash and a \jt^lLi/r* 

 drop of copper sulphate (it gives a clear blue fluid), and heat. fijLitJU 

 With a pure sugar there should be no reduction. 



84. Pour strong sulphuric acid on a little dry cane sugar 

 in a test-tube. Add a few drops of water with a pipette, the '1^ 

 whole mass is quickly charred. ^ 



85. Boil a solution of cane sugar with a little sulphuric 

 acid added. Neutralize the solution with a little sodium car- 

 bonate and test for dextrose. 



86. Apply Barfoed's, Boettger's and the phenyl-hydra- 

 zine tests to portions of the cane sugar solution and note if 

 any reduction occurs. 



