64 HOW CROPS GROW. 



thin, and destitute of the ropiness of cane-sugar syrup. 

 It does not crystallize (granulate) so readily as cane- 

 sugar. 



Exp. 30.— Mix 100 o. o. of water with 30 drops of strong sulphuric acid, 

 and heat to vigorous boiling in a glass flask. Stir 10 grams of starch 

 with a little water, and pour the mixture into the hot liquid, drop by 

 drop, so as not to interrupt the boiling; The starch dissolves, and passes 

 successively into amidulin, dextrin, and dextrose. Continue the ebul- 

 lition for several hours, replacing the evaporated water from time to 

 time. To remove the sulphuric acid, add to the liquid, which may be 

 still milky from impurities in the starch, powdered chalk, until the sour 

 taste disappears ; filter from the calcium sulphate (gypsum) that is 

 formed, and evaporate the solution of dextrose* at a gentle heat to a 

 syrupy consistence. On long standing it may crystallize or granulate. 



By this method is prepared the so-called grape-sugar, or starch-sugar 

 of commerce, ■which is added to grape-juice for making a stronger 

 wine, and is also employed for preparing syiups and imitating molasses. 

 The syrups thus made from starch or com are known in the trade as 

 glucose.^ Imitation-molasses is a mixture of (fextrose-syrup with some 

 dextrin to make it " ropy." 



Eren cellulose is conTertible into dextrose by the pro- 

 longed action of hot acids. If paper or cotton be first 

 dissolved in strong sulphuric acid, and the solution 

 .diluted with water and boiled, the cellulose is readily 

 transformed into dextrose. Sawdust has thus been made 

 to yield an impure syrup, suitable for the production of 

 alcohol. 



In the formation of dextrose from cellulose, starch, amidulin and 

 dextrin, the latter substances take. up the elements of water as repre- 

 sented by the equation 



Starchy etc. Water. Glucose. 



CbHioOb + HjO = CoHuOe 



In this process, 90 parts of starch, etc., yield 100 parts of dextrose. 



Trammer's Copper test.— A. characteristic test for dextrose and levu- 

 lose is found in their deportment towards an alkaline solution of cop- 

 per, which readily yields up oxygen to these sugars, the copper being 

 reduced to yellow cuprous hydroxide or red cuprous oxide. - 



Exp. 31.— Prepare the copper test by dissolving together in 30 c. o. of 

 warm water a pinch of sulphate of copper and one of tartaric acid ; 

 add to the liquid, solution of caustic potash vuitil It acquires a slip- 



* If the boiling has been kept up but an hour or so, the dextrose will 

 contain dextrin, as may be asceAained by mixing a small portion of 

 the still acid liquid with 6 times its bulk of strong alcohol, which will 

 precipitate dextrin, but not dextrose. 



t Under the name glucose, the three sugars levulose, dextrose and 

 maltose were formerly confounded together, by chemists. 



