THE CARBOHYDRATES 139 



^12^1404.3804, and a nitrate is obtainable having the formula C12H14O4. 

 6NO3. The reaction by which this is produced shows that the cellulose 

 contains hydroxyl groups like metallic hydroxides. Just as 



KOH + HNO3 = KNO3 + H2O, 

 so C12H14O4. 60H + 6HNO3 = C12H14O4. 6NO3 + 6H2O. 

 It is obvious, therefore, that if cellulose has the formula CgHioOg it could 

 not form a hexanitrate, for there could not be six replaceable hydroxyl 

 groups. 



The nitrate is produced by the action of a mixture of nitric and sulphuric 

 acids on cotton wool, the object of the sulphuric acid being to combine 

 with the water as it is liberated. If allowed to act for a short time only, 

 the tri-, tetra-, or penta-nitrates are produced, which, when dissolved in 

 alcohol and ether, constitute collodion. If the action is prolonged the 

 hexanitrate— gun-cotton — is formed. Both cotton and flax consist of 

 nearly pure cellulose. Cotton and linen rags, together with the impure 

 cellulose constituting the fibre of straw and wood, are utilised in the 

 manufacture of paper. For this purpose these materials are completely 

 disintegrated and made into a pulp with water, which is then passed 

 between rollers. 



Procure some cane sugar and grape sugar. To a solution of 

 each add copjoer sulphate solution and then potash till alkaline. 

 Note that in neither case is a precipitate obtained, owing to 

 the property that sugars possess of forming soluble compounds 

 with many basic oxides. Now warm the solutions. Note 

 that the cane sugar solution is unchanged, but that the grape 

 sugar reduces the cupric to red cuprous oxide, which is precipi- 

 tated. Warm another portion of the cane sugar solution with 

 dilute sulphuric acid for a few minutes, and repeat the test. 

 Note that the cupric oxide is now reduced to cuprous, show- 

 ing that grape sugar has been formed by warming the cane 

 sugar with acid. 



" Cane sugar " occurs in unripe fruits and in the sap of plants, especially 

 the sugar cane, sugar maple, sorghum, and sugar beet. Sugar is pre- 

 pared from these. An aqueous solution is obtained, which is decolorised 

 by animal charcoal and evaporated till crystallisation commences. Among 

 agricultural crops, mangolds and beet are the richest in sugar. " Grape 

 sugar" occurs, together with an equal quantity of "fruit sugar," in ripe 

 fruits, obviously produced from the cane sugar in the unripe fruit. It is 



