-- By EDTA Titration^1,2

zncal.doc 06/22/98

Zinc stock solution (~.0075 M)

pH 10 buffer solution

1% Eriochrome Black T (or Erio T) indicator

dilute sodium hydroxide (3 M)

A.2 Prepared by Student

0.01 M EDTA solution, 100 mL (See Appendix I)

 

B. Equipment

50 mL graduated buret

3 250 mL conical flasks

25 mL graduated cylinder

50 mL pipet

dropper

100 and 250 mL volumetric flasks

pH paper

C. Procedures

C.1 Triple rinse and fill the 50 mL buret with the 0.01M EDTA solution. Drain some solution to fill the tip of the buret. Record initial volume.

C.2 Pipet 50 mL of the zinc stock solution into a 250 mL volumetric flask. Dilute to the mark with deionized water. Pipet 50 mL of the diluted zinc solution to a 250 mL conical flask. Test the pH of the diluted solution with pH paper. If acidic, add dilute sodium hydroxide dropwise (about 1 - 2mL) to around neutral pH. Then add about 2.5 mL of the pH 10 buffer and 2 to 5 drops of 1% Erio T indicator.

C.3 Stir (swirl) the solution mixture in C.2. Titrate it with the 0.01M EDTA solution. The end point should be a sharp color change from rose-pink to blue. Record the final volume of the EDTA solution. Repeat procedure C.2 to C.3 twice.

_______________________________________________________________

(1) Welcher, The Analytical Uses of Etylenediaminetetracetic Acid, 1958.

(2) Vogel, Textbook of Quantitative Inorganic Analysis, 1961.

 

 

 

D. Report

D.1 Record the following data in your Lab Notebook and in the Zinc Solution Certification Notebook.

a. Weighing data, calculations, and EDTA solution concentration.

b. Volumetric data for three titrations

c. Average Zinc concentration and standard deviation

D.2 Sign and date the Zinc Notebook, and label the Zinc stock solution vessel with the up-dated certified concentration, date certified, and your name.

 

Click here to view and/or print the Table for this section

Click here to view and/or print the Sample Table for this section