FOODS 109 



boiling for two to six minutes, when there should be a red 

 precipitate and the liquid should still be blue. Now filter 

 rapidly, washing the precipitate at first by decantation 

 and then on the filter-paper, until the washings contain 

 no copper. Dry, ignite, and weigh as CuO (black copper 

 oxide). Weight X 0-4308 gives cane sugar, and 

 X 0-4535 gives glucose. The CuO is hygroscopic ; therefore, 

 for accuracy, at least two ignitions and two weighings are 

 necessary. Also prolonged ignition is needed to oxidize all 

 the Cu 2 (the filter-paper having a reducing action). 



Insoluble Mineral Matter. Dissolve a considerable 

 amount in water, filter on to weighed paper, dry, and weigh. 



Colouring Matter. Extract with alcohol and steep a 

 piece of wool mordanted with aluminium acetate. Aniline 

 dyes are dissolved and stain the wool. The natural 

 colour is not so removed. Ultramarine is used to 

 " whiten " sugar, as also is methyl- violet, both correcting 

 the slight yellow tint natural to sugar. To fix the natural 

 yellow tint, chloride of tin was formerly used, but not now. 

 Demerara sugar is made by adding sulphuric acid to the 

 massecuite (the finished mass of sugar crystals and syrup 

 formed by concentrating syrup in a vacuum pan) so as to 

 slightly char the sugar grains. About 3 gallons of pure 

 sulphuric acid, diluted with 1-5 gallons of water, are used 

 for 5 tons of sugar. This gives the bright yellow colour 

 so much admired. Animal charcoal, sulphurous acid, and 

 peroxide of hydrogen are also used in various processes. 



The sample is dyed if, when treated with a few drops of 

 concentrated HC1, a pink colour forms. 



Sugar Mite, or Acarus sacchari, by microscope. 



Sugar of Milk or Lactose is made on the large scale from 

 whey or skimmed milk. 



Glucose, or Starch Sugar, is made on the large scale from 

 the starch of maize, potato, rice, and sago, by treating 

 with weak (pure) mineral acid, aided by boiling under 

 increased pressure until some of the liquid added to alcohol 

 gives no precipitate of dextrin or no iodine reaction. The 

 acid is then carefully neutralized and the resulting glucose 

 solution refined. Poisoning has arisen from the use of 

 impure sulphuric acid in the process (arsenic in beer). 



