126 GLYKOSE. 



decanted liquor to a thin syrup, from which in a few 

 weeks the glucose will crystallise out. 



2. Heat some glucose with a solution of bichromate 

 of potash and sulphuric acid in a test tube furnished 

 with a cork and delivery tube ; pass the evolved 

 vapours into a solution of nitrate of silver; formic 

 acid will be evolved, which will reduce and blacken the 

 silver solution. 



3. Add some cold concentrated sulphuric acid to 

 glucose ; the latter will dissolve without blackening ; 

 cane sugar blackens. 



4. Dissolve some glucose in water, add caustic 

 potash solution, and a drop or two of very dilute 

 copper sulphate solution; after long standing in the 

 cold, or immediately on boiling, the copper salt will be 

 reduced, and a bright red precipitate of copper sub- 

 oxyde falls. 



5. Add a solution of glucose to a solution of silver 

 nitrate and heat gently ; the silver salt is reduced, and 

 metallic silver is deposited either as a black powder or 

 as a mirror-like coating. 



6. Dissolve two parts of ferricyanide of potassium 

 and one part of hydrate of potassium in water, warm, 

 and add aqueous solution of glucose. The solution 

 will be decolorised. Neither cane sugar nor dextrine 

 give this reaction. 



7. To an aqueous solution of glucose add a concen- 

 trated solution of common salt, and allow to stand ; 

 crystals of chloride of sodium and glucose separate. 

 These crystals will be formed if diabetic urine be 

 evaporated and allowed to stand. 



