How to test the chloride ion content in zinc sulfate?

Too much chlorine ion in the zinc sulfate would cause spurious agglomeration. How to count out the chloride ion content in zinc sulfate? 

Add water in 1 ~ 10 mL zinc sulfate solution as to 150 mL in 250mL-conical flask, and add bromophenol blue indicator (1 g/L) 5 drops. Use sodium hydroxide solution (300 g/L) to adjust the solution color till blue and add nitric acid (5 + 95) to switch to yellow and excessive 5 drops (PH 3.0 ~ 3.5 at this time. For electrolytic liquid color interference the result, it’s better to use precise PH test paper regulation). Plus indicator agent phenylazoformic acid 2-phenylhydrazide (5 g/L) 1.0 mL and titrate mercury nitrate standard solution to purple finally.

Calculate the chloride content as bellow:
T_CL * 1000* V₂
C_CL (mg/L) = -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -
V₁
C_CL - mease chlorine concentration in test solution (mg/L)
T_CL –the titration coefficient of chloride with mercury nitrate standard solution for (mg/mL)
V₁- the test fluid volume (mL)
V₂ - titration consumption volume of mercury nitrate standard solution (mL)

On the Current market, chloride ion content in zinc sulfate is 1.5 ~ 1.8 PPM, however, chloride ion content of zinc sulfate produced by Rech Chemical Co. Ltd is lower than this value that the quality would be better.



By the way, you can find " Why zinc sulfate appeared the phenomenon of agglomeration " in our website.