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1 University of Mosul College of Pharmacy Practical Laboratory Dept. of Pharmaceutical Chemistry Head of dept. Dr. ؤىوىست Nohad Al.Omari Directed by Ph. Sadeel Shanshal 0

2 Syllabus : No. Lab. Title Hours 1. Preparation and standardization of 0.1 N KMnO 4 (known sample) Preparation and standardization of 0.1 N KMnO 4.(quiz & unknown) Assay of Hydrogen peroxide solution.(known sample) Assay of Hydrogen peroxide solution.(quiz & unknown) 2 5. Assay of Ferrous sulfate (known sample) Assay of Ferrous sulfate (unknown sample) Preparation and standardization of 0.1 Na 2 S 2 O 4 sol.(known sample) Preparation and standardization of 0.1 Na 2S 2 O 4 sol.(quiz & unknown). 9. Assay of copper sulfate (known sample) Assay of copper sulfate (unknown sample) Assay of Chloinated Lime (known sample) Assay of Chloinated Lime (quiz & unknown) Preparation and Assay of Lugol s Solution. (known sample) Preparation and Assay of Lugol s Solution. (quiz & unknown) Assay of Alum (unknown sample)

Experiment No.1 The preparation and Standardization of 0.1 N Potassium Permanganate Solution Objective: Preparation and standardization of one liter of 0.1 solution KMnO 4.

3 Experiment No.1 The preparation and Standardization of 0.1 N Potassium Permanganate Solution Objective: Preparation and standardization of one liter of 0.1 solution KMnO 4. Introduction: KMnO 4 is strong oxidizing agent, it will oxidize any organic matter present in distilled water, its color act as indicator in the titration. It possesses disinfectant and deodorant properties. Chemical principle: Oxidation reduction titration ( Redox titration ) 1

4 Procedure: Dissolve about 3.3 g of KMnO 4 in 1000 ml of water in a stopped flask, allow to stand for at least 2 days,and filter through asbestos. Standardization the solution is as follows: Weigh accurately about 200 mg of sodium oxalate previously dried at 110 C to a constant weight and dissolve it in 250ml of water, add 7ml of sulfuric acid and heat to about 70 C, then slowly add the permanganate solution from a burette,with constant stirring until a pale pink color which persists for 15 seconds is produced the temperature at the end of the titration should not be less than 60 C. Review Questions : 1- Why we used 3.3g KMnO 4 to prepare 1L of 0.1 N solution? 2- Durine the Standardization, the temperature should not be less than 60 C, why? 2

5 Experiment No.2 Assay of Hydrogen Peroxide Solution Objective: Calculate the % of hydrogen peroxide in an unknown solution. Introduction: It is an aquous solution of H 2 O 2, colorless, oderless liquid, used as antiseptic and deoderant. Chemical principle: Hydrogen peroxide solution is titrated with potassium permanganate solution in acidic medium at room temperature. 3

6 Procedure : In conical flask dilute10 ml of H 2 O 2 solution with 200 ml distill water, transfer 20 ml of dilute solution, add 5 ml of sulphuric acid ( 50% w/v ), then titrate with 0.1 N potassium permanganate until the solution colour become pink at end point.each 1 ml of 0.1N KMnO 4 is equivalent to g of H 2 O 2. Review Questions: 1- Calculate the chemical factor for H 2 O 2 which is equivalent to 1ml of 0.1 N KMnO 4? 2- Define self oxidation reduction reaction. 4

Experiment No.3 Assay of Ferrous Sulfate(FeSO 4.7H 2 O) Objective: Calculate the weight of ferrous sulfate in an unknown sample. Introduction: It is bluish green crystals freely soluble in water, M.

7 Experiment No.3 Assay of Ferrous Sulfate(FeSO 4.7H 2 O) Objective: Calculate the weight of ferrous sulfate in an unknown sample. Introduction: It is bluish green crystals freely soluble in water, M.wt = 278 g, used as a source of iron in anemia. Chemical principle: Ferrous sulfate is a reducing agent which is titrated against standard oxidizing agent solution ( KMnO 4 Solution ) in acidic medium. Procedure: Dissolve about 1 g accurately weighed of FeSO 4.7H 2 O in 20 ml of dilute sulphuric acid and titrate with N/10 potassium permanganate. Each ml of 0.1 N potassium permanganate is equivalent to gm of FeSO 4.7H 2 O Review Questions: Calculate the chemical factor of ( FeSO 4.7H 2 O) which is equivelant to 1ml of 0.1 N KMnO 4? 5

8 Experiment No.4 The Preparation and Standardization of 0.1 N Sodium Thiosulphate Solution Objective: Preparation and standardization of one liter 0.1 N Sodium thiosulphate solution. Introduction: White granular compound M.wt 248, freely soluble in water. It is used as antifungal agent. Chemical principle for the Standardization of Sod. Thiosulphate: Potassium dichromate is an oxidizing agent, it is reduced by excess KI in acidic media and an equivalent amount of iodine is formed (liberated). The liberated iodine is titrated with sodium thiosulphate solution using starch indicator. This indirect procedure is known as iodometry. 6

9 Procedure: Dissolve about 26 gm of sodium thiosulphate and 200 mg of sodium carbonate in 1000 ml of recently boiled and cooled water. Standardization: Weigh accurately about 200 mg of primary standard potassium dichromate ( K 2 Cr 2 O 7 ) previously dried at 120 C for 4 hours and dissolve in 100 ml of water in a glass stoppered flask, swirl to dissolve the sample,remove the stopper and quickly add 3 g of potassium iodide, 2 g of sodium bicarbonate and 5ml of concentrated hydrochloric acid. Stopper the flask, swirl to mix and allow to stand in dark place for 10 minutes, rinse the stopper and the inner walls of the flask with water and titrate the liberated iodine with sodium thiosulphate solution until the solution is faintly yellow in color, add starch mucilage and continue the titration to the discharge of the blue color calculate the normality. Review Questions : Why did you use 26 gm sodium thiosulphate to prepare 1L of 0.1 N solution? 7

Experiment No.5 Assay of Copper Sulphate CuSO 4.5H 2 O Objective : Calculate the % of copper sulphate in an unknown solution. Introduction: Blue,fine crystalline powder, contain not less than 98.

10 Experiment No.5 Assay of Copper Sulphate CuSO 4.5H 2 O Objective : Calculate the % of copper sulphate in an unknown solution. Introduction: Blue,fine crystalline powder, contain not less than 98.5 % and not more than 101% w/w CuSO 4. H 2 O. It is used as fungiside, algeside, as a component of fehlings and Benedicts solutions. Chemical principle: CuO 4 is treated with excess potassium iodide in acidic media,cupric iodide is formed which is unstable and will break up into cuprous iodide and iodine.the liberated iodine is titrated with standard sodium thiosulfate solution. 2CuSO 4 + 4KI 2CuI 2 + 2K 2 SO 4 2CuI 2 2CuI (Cu 2 I 2 ) + I 2 cuprous iodide I 2 + 2Na 2 S 2 O 3 2NaI + Na 2 S 4 O 6 The liberated iodine is adsorbed by the precipitated coprous iodide.the addition of potassium thiocyanate near the end point forms coprous thiocyante,and tends to free the adsorbed iodine. KSCN + CuI CuSCN + KI 8

11 Procedure : Dissolve about 1 g accurately weighed in 50 ml of water, add 1.5 gm of potassium iodide, and 5 ml of acetic acid and titrate the liberated iodine with N/10 sodium thiosulfate,using starch mucilage as indicator,and continue the titration until the blue color disappears. Review Questions: 1- Excess of Potassium iodide must be added in this assay why? 2- Why you added Potassium thiocyanade near the end point? 9

Experiment No.6 Assay of Chlorinated Lime, Bleaching powder,chloride of Lime Calcium Chloro hypochlorite Ca(OCl )Cl Objective : Calculate the % of available chlorine in an unknown solution.

12 Experiment No.6 Assay of Chlorinated Lime, Bleaching powder,chloride of Lime Calcium Chloro hypochlorite Ca(OCl )Cl Objective : Calculate the % of available chlorine in an unknown solution. Introduction: Contain not less than 30% w/w available chlorine, white powder with characteristic odor. It is used as disinfectant. Chemical principle: Ca(OCl )Cl + 2CH 3 COOH (CH 3 COO) 2 Ca +HOCl +HCl HOCl +HCl Cl 2 + H 2 O Cl 2 + 2KI 2KCl +I 2 2Na 2 S 2 O 3 +I 2 2NaI + Na 2 S 4 O 6 Aqueous solution of the substance is treated with acetic acid in the presence of excess KI. Acetic acid like other acid liberates chlorine from chlorinated lime and the liberated chlorine displaces an equivalent amount of iodine from potassium iodide, the iodine produced is titrated with N/10 sodium thiosulphate using starch mucilage as indicator. 10

13 Procedure : Treat about 4 g accurately weighed with small quantities of water and transfer to a liter volumetric flask. Dilute to 1000 ml with water and shake thoroughly. Mix 100 ml of this suspension with a solution of 3 g. of potassium iodide in 100 ml of water, acidify with 5 ml of acetic acid, and titrate the Liberated iodine with N/10 sodium thiosulphate. Each ml of N/10 sodium thiosulphate is equivalent to g of available chlorine. Review Questions: 1- Define available chlorine? 2- Calculate the weight of available chlorine which equivalent to 1ml of 0.1 N sodium thiosulphate solution? 11

14 Experiment No.7 The preparation and assay of Aqueous Iodine Solution (Lugol s Solution ) Objective: Preparation and calculation the % w/v for I 2 and the % of w/v for KI. Introduction: It contain 5% w/v I 2 and 10% w/v KI, used in preoperative treatment of thyrotoxicusis. Iodine I 2 50 g Potassium iodide KI 100 g Purified water,sufficient to produce 1000 ml Dissolve the potassium iodide and the iodine in 100 ml of purified water and add sufficient purified water to produce 1000 ml. Procedure : Dilute 25 ml with water to 100 ml. 12

15 Assay of Iodine: To 20 ml of the diluted solution of I 2 add 10 ml of water and titrate with N/10 sodium thiosulphate, add 1 ml of starch, and titrate until the colour change from blue to colorless at end point. Each ml of N/10 sodium thiosulphate is equivalent to gm of iodine. Assay of potassium iodide: To 10 ml of the diluted solution,add 20 ml of water and 40 ml of hydrochloric acid and titrate with M/20 potassium iodate until the dark brown solution which is formed becomes pale brown, add 1 ml of a maranth solution and continue the titration until the red color just changes to pale yellow. Form the number of ml of M/20 potassium iodate required subtract one quarter of the number of ml of N/10 sodium thiosulphate required in the assay for iodine.each ml. of the remainder is equivalent to gm of KI. Chemical principle: Potassium iodate is a fairly strong oxidizing agent,it can react quantitatively with both iodide and iodine. If the concentration of hydrochloric acid doesn t exceed IN the reaction between potassium iodate and potassium iodide stops when the iodate is reduced to free iodine. KIO 3 + 5KI +6HCl 6KCl +3I 2 +3H 2 O In the presence of concentrated hydrochloric acid exceeding 4N, the iodine produced by the above reaction is further oxidized to iodine monochloride. KIO 3 + 2I 2 +6HCl KCl +5ICl + 3H 2 O 13

16 The reaction between potassium iodate and potassium iodide in the presence of a high concentration of hydrochloric acid ( 4N ) is expressed by the following equation : KIO 3 +2KI+6HCl 3KCl + 3ICl + 3H 2 O Review Question : 1- Why we used M/20 KIO 3 while Na 2 S 2 O 3 N/10 solution? 2- Why we use 20 ml solution for the assay of I 2 solution while we use 10 ml solution for the assay of KI solution? 14

17 Experiment No.8 Assay of Alum Objective : Calculation the % w/w of Alum in the an unknown solution. Introduction: Alum is either Potassium Alum, M.wt 453.3, Potassium aluminium suphate KAl(SO 4 ) 2.12H 2 O (M.wt ), or Ammonia Alum, ammonium aluminium sulphate NH 4 Al(SO 4 ) 2.12H 2 O (M.wt ), use as stringent. Chemical principle: Compleximetric back titration method: An excess of a standard disodium edetate solution is added to the sample and the resulting solution is buffered to the desired ph and an excess of reagent ( that means disodium edetate ) is back titrated with a standard metal ion solution,(lead nitrate Solution ). Procedure: Dissolve about 1.7 g accurately weighed of Alum, in sufficient water to produce 100 ml to 20 ml add 30 ml of N/20 disodium editate and 100ml of water, heat on a water bath for ten minutes, cool, add 5 g of hexamine,and titrate with N/20 lead nitrate solution,using 0.4 ml of xylenol orange solution as indicator.each ml of M/20 disodium edetate is equivalent to g of KAL(SO 4 ) 2.12H 2 O or g of NH 4 Al(SO 4 ) 2.12H 2 O. Review Questions: 1- Why do you heat the solution during the assay? 2- Hexamine is added in this assay, why? 15

EXPT. 8 IODOMETRIC DETERMINATION OF AVAILABLE CHLORINE IN A SAMPLE OF BLEACHING POWDER

EXPT. 8 IODOMETRIC DETERMINATION OF AVAILABLE CHLORINE IN A SAMPLE OF BLEACHING POWDER Structure 8.1 Introduction Objectives 8. Principle 8.3 Requirements 8.4 Solutions Provided 8.5 Procedure 8.6 Observations