Anhydrous sodium lactate benchmark

Calibration: at 270-300 ℃ drying to constant weight basis anhydrous sodium carbonate is about 1.5g, accurately weighed, add water to dissolve 50mL, add methyl red - bromocresol green mixed indicator solution 10 drops of the droplet to solution from green to purple, boil for 2 minutes, cooled to room temperature and continue the titration until the solution color green to dark purple. Each 1mL of sulfuric acid buffered lactic acid (0.5mol / L) is equivalent to 53.00mg of anhydrous sodium carbonate. According to the liquid consumption of anhydrous sodium carbonate dosage, calculated the concentration of the solution, that is, too.
3 phenolphthalein indicator solution
Take phenolphthalein 1g, plus ethanol 100mL dissolve.
4 bromocresol green mixed indicator solution
0.1% methyl red ethanol solution of 20mL, plus 0.2% bromocresol green in ethanol 30mL, shake, that, too.

Procedure: Sodium lactate test sample 1g, accurately add water 50mL, precision by adding sodium hydroxide solution (1mol / L) 25mL, boiled for 5 minutes, add 2 drops of phenolphthalein indicator solution, hot sulfuric acid titration solution (0.5mol / L) titration, to the solution was pink, and titration of the blank test correction, record consumption of sulfuric acid titrant volume number (mL), each 1mL of sodium hydroxide (0.1mol / L) is equivalent to 90.08mg lactic acid (C3H6O3).
Note 1: "Precision Weigh" means to check the weight should be accurately referred to take the weight of one-thousandth, "precise amount" means the amount of volume accuracy should be in line with national standards for the volume pipettes accuracy requirements.