eutech-instruments chloride epoxy User Manual

Instruction Manual 

 

Chloride Electrode 

 

12

 

1.  Acidify with 1M HNO

3

 to pH 4 to remove hydroxide interference. 

 
2. These substances represent complexing species whose maximum level can be exceeded 

without electrode damage. Value shown represents a 1% error. 

 
3. Add CISA to solutions containing mixed halides to remove interferences. See the 

procedure below. 

 
4.  Add CISA or a solution of Ni

+2

 to remove sulfide or cyanide interferences. 

 

 
CISA is an oxidizing agent which will oxidize up to a 100-fold excess of CN

-1

 over Cl

-1

, 100 ppm 

NH

3

, 100 ppm Br

-1

 or I

-1

, or 500 ppm S

-2

. Chloride measurement interferences may be removed by 

using CISA. The reagents used to prepare CISA are strong oxidizing agents and should be handled 
in a fume hood. 
 
To prepare CISA, add approximately 800 ml of distilled water to a 1 liter volumetric flask. Add 
15.1 grams of NaBrO

3

 to the flask and swirl to dissolve the solid. Slowly add 75 ml of concentrated 

nitric acid (70% w/w or 15.9N), mix, and dilute to the mark with distilled water. 
 
To use CISA, mix equal amounts of CISA and sample.  Solutions should be allowed to stand for ten 
minutes before measuring. Since chloride will be oxidized upon prolonged standing, all standards 
or samples mixed with CISA should be discarded after measuring. A fresh mixture of CISA and 
standard should be prepared for each calibration. After adding CISA, follow the procedures for 
direct measurement. 

 
Total concentration (Ct) consists of free ions (Cf) and complexed or bound ions (Cc) in solution: 
 

Ct = Cf + Cc 

 

Since the electrode only responds to free ions, any complexing agent in the solution reduces the 
measured concentration of ions.