Copper content in copper oxychloride

ESTIMATION OF COPPER CONTENT IN COPPER OXYCHLORIDE (FYTOLAN)

Principle

         Cupric ions (cupric nitrate) are formed when copper oxychloride (formula Cu (OH) 2 CuCL2: Molecular weight 231.98) is treated with nitric acid. The cupric ions thus formed are converted to cuprous iodide and iodine by the addition of potassium iodide. The iodine so liberated is titrated against standard sodium thiosulphate. The absorption of iodine on cuprous iodide precipitate is avoided by the addition of potassium or ammonium thiocyanate.

Reactions

Cu (OH) 2 CuCl2+2HNO3                                

→

Cu (NO3)2+ CuCl2+ 2H2O

2Cu (NO3)2+ 4KI                                                  

→

2CuI2+ 4KNO3

        2CuCl2+4KI                             

→

2Cul2+I2

         2CuI2                                       

→

Cu2I2+I2

I2+2NaS2O3                                 

→

Na2S4O6+2NaI

 2Cu=I=2Na2S2O3

Materials required

i)                    Dilute acetic acid (10%), ii) Nitric acid, iii) Urea, iv) Sodium thiosulphate (0.1N),v) Sodium carbonate, vi) Potassium iodide, vii) Potassium/Ammonium thiocynate, viii) Starch indicator, ix) Erlenmeyer flask.

Procedure

v  Transfer accurately a quantity of material containing 0.1 to 0.2g of copper into a 500ml Erlenmeyer flask.

v  Add 5ml of distilled water and 5ml of concentrated nitric acid or 10ml of 1:1 nitric acid. Shake and then warm the mixture and reduce the volume to 5ml.

v  Add 30ml of distilled water and boil the contents for about 5minutes.

v  Remove the flask from the flame and add 1g of urea and boil the contents again for about 10min.

v  Cool the flask to room temperature and add sodium carbonate in small quantities till a faint permanent precipitate or blue colour is obtained.

v  Add dilute acetic acid drop by drop until the blue colour disappears/precipitate dissolves.

v  Add 1.5-2.0g of potassium iodide and titrate the brown solution immediately with standard sodium thiosulphate till a light yellow/pale straw colour is obtained.

v  Add about 2ml of freshly prepared starch indicator solution and 1g of potassium or ammonium thiocynate and continue the titration till the blue colour just disappears.

v  From the actual volume of sodium thiosulphate consumed calculate the copper content of the fungicide.

Calculation

Actual volume of 0.1N Na2S2O3 consumed by liberated iodine

=

V ml

Weight of fungicide sample taken

=

W g

1000ml of 1N Na2S2O3 

=

63.54 g of Cu

1ml of1N Na2S2O3

=

0.06354g of Cu

1ml of 0.1N Na2S2O3

=

0.006354 g of Cu

V ml of 0.1N Na2S2O3

=

0.006354 X V g of Cu

This present in Wg of sample

Therefore in 100g of sample

=