Bertrand Method

Bertrand Method (Bertrand), for determining sugar, is based on the fact that copper oxide is reduced by a carbohydrate to cuprous oxide, which converts the ferrous sulfate salt to the corresponding ferrous salt, which is then determined by titration.

Apparatus for determining sugar by Bertrand's method: 1 - asbestos; 2 - glass wool; 3 - to pump.

Reagents: 1) copper sulfate - 40 g, water to 1 l; 2) Rochelle salt - 200 g, sodium hydroxide 150 g, water to 1 l; 3) ferrous sulfate 50 g, sulfuric acid 200 g, water to 1 l; 4) potassium permanganate 5 g, water to 1 l. The titer of this solution is determined by ammonium oxalate. - Procedure: to 20 cubic cm of the test liquid, which must be free from protein and contain no more than 100 mg of sugar, add 20 cubic cm each of solutions 1 and 2, boil for 3 min. Filter through asbestos using a water jet pump, trying as much as possible to leave the formed cuprous oxide in the flask; dissolve the latter in 5-20 cubic cm of solution 3; pass the liquid through the same asbestos, washing with distilled water, and titrate the ferrous iron with potassium permanganate. Calculation is done using special tables, different for each type of reducing sugar. This method is very precise; it is used for determining all reducing sugars, in particular, for determining the quantity of sugar in urine. By Anbar (Anbard), this method has been modified as a micromethod based on the same principle.