Division 4.3 Standard invert sugar solution: dissolve 23·750 g of pure sucrose in about 120 ml of water in a 250 ml graduated flask, add 9 ml of hydrochloric acid (ζ = 1·16) and allow to stand for eight days at room temperature. Make the solution up to 250 ml and check for completion of hydrolysis by a polarimeter or saccharimeter reading in a 200 mm tube. This should be - 11·80o ± 0·05 oS (see note 8). Pipette 200 ml of this solution into a 2 000 ml graduated flask. Dilute with water and while shaking (to avoid excessive local alkalinity) add 71·4 ml of sodium hydroxide solution (1 mol/litre) (4.2) in which 4 g of benzoic acid has been dissolved. Make up to 2 000 ml to give a 1 g/100 ml solution of invert sugar. This solution should be a pH of approximately 3.
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This stable stock solution should only be diluted immediately before use.
To make up the 0·25 g/100 ml invert sugar solution, fill a 250 ml graduated flask to the mark with the stock 1 g/100 ml invert solution at 20 oC. Wash the contents of this flask into a 1 000 ml graduated flask and dilute to the mark with water again at 20 oC.