Steps to calibrate acid concentration by Tris and sodium carbonate titration

Tris is a weak base with a wide range of uses. It can be used in biological buffers, biopharmaceuticals, coatings, new composite materials, etc. Sodium carbonate is the reference substance for titration calibration of acid concentration, but it has some shortcomings, and Tris can be used as a supplement to sodium carbonate reference substance to replace it for titration calibration of acid concentration.

Tris(hydroxymethyl)aminomethane Tris

Experiment preparation and equipment:

Hydrochloric acid: analytically pure; sulfuric acid: analytically pure; sodium carbonate: reference reagent; Tris: reference reagent; methyl red-cresol green ethanol solution. Potentiometric titrator, Lab X workstation, composite pH electrode; muffle furnace; 50mL acid burette and other general laboratory utensils.

Use Tris and sodium carbonate to titrate hydrochloric acid or sulfuric acid separately:

Manual titration: Weigh the standard reagent Tris (constant weight at 110 degrees Celsius) or anhydrous sodium carbonate (constant weight at 270-300 degrees Celsius) which consumes about 20-30 mL of the sulfuric acid or hydrochloric acid titration solution to be calibrated, weigh to 0.0001g, and dissolve in Add 10 drops of bromocresol green-methyl red indicator to a 250mL Erlenmeyer flask containing 50~100mL of water, and change the acid solution to be calibrated from green to dark red. Boil for 2min. After cooling, continue to titrate until the solution just changes color ( Light gray). Do a blank test for the acid standard titration solution of not more than 0.1mol/L at the same time.

Automatic potentiometric titration: Fix the titration cup containing the reference anhydrous sodium carbonate or Tris aqueous solution on the titration stand, connect the PH composite electrode, set the appropriate titration parameters of the automatic potentiometer, and start the titration program to automatically titrate to the end point. (It is appropriate to consume sulfuric acid or hydrochloric acid titrant 2. ~ 30mL). At the same time, make a blank test.

Compared with manual titration, automatic potentiometric titration has more advantages. Manual titration adopts calibration indicator. The selection is based on the sudden change in the pH value of the solution near the stoichiometric point of the titrant. The end point is judged by the color change of the indicator, and the color range is affected by different concentrations. The acid content and the quality of the reference material vary. Usually, the indicator method must be used to calibrate the end point color by the potentiometric method.

Potentiometric titration is based on potential mutation sites. The potential mutation sites of Tris are more prominent and single, while sodium carbonate has multiple interference mutation sites. Tris potential titration has more advantages in calibrating acid concentration. Desheng has a large-scale Tris production line, and its products are stable and guaranteed.