preparation and standardization of sodium thiosulfate.pptx

preparation and standardization of sodium thiosulfate solution

1. Inorganic pharmaceutical chemistry I 4th lab. Preparation & Standardization of Sodium Thiosulphate Solution Ali M.saeed M. Sc. Pharmceutical chemistry University of Al-Ameed College of Pharmacy 15/10/2024 Third stage 1 st semster

2. Introduction It is typically found in its pentahydrate form which is either white in colour , or colourless altogether. This pentahydrate of sodium thiosulfate is described by the following chemical formula: ) Na 2 S2O 3 .5H 2 O. ( In its anhydrous form, sodium thiosulfate has a molar mass of 158.11 grams per mole. The more commonly available pentahydrate from, Na 2 S 2 O 3 .5H 2 O has a molar mass of 248.18 g/mol.

3. Medical uses Sodium thiosulfate is used in the treatment of cyanide poisoning . Other uses include topical treatment of ringworm , tinea versicolor , and treating some side effects of hemodialysis and chemotherapy . Its effective treatment for calciphylaxis, a rare but serious vascular calcification disorder predominantly seen in patients with dialysis-dependent end-stage kidney disease

4. Aim To determine the normality of given sample of sodium thiosulphate .

5. Principle The principle of standardization of sodium thiosulphate is based on redox iodometric titration with potassium iodate ( primary standard ). Potassium iodate is a strong oxidizing agent, it is treated with excess potassium iodide in acidic media which liberates iodine which is back titrated with sodium thiosulfate.

6. Principle (cont.) Reactions between iodine and sodium thiosulphate forms basis for utilizing the standard solution of iodine in the analysis of sodium thiosulphate. Sodium thiosulphate is used in the analysis of iodine. In the analysis of iodine starch solution is used as indicator. KIO 3 + 5KI + 3H 2 SO 4 → 3K 2 SO 4 +3I 2 +3H 2 O I 2 +I - → I 3 - I 2 +2Na 2 S 2 O 3 → 2NaI + Na 2 S 4 O 6 What’s the point Why excess KI sod. tetrathionate

7. Preparation of 0.1N sod. thiosulfate Dissolve 2.48 g of sodium thiosulphate pentahydrate (Na2S2O3.5H2O) in 80 ml of freshly boiled and cooled water and mix thoroughly by shaking for approximately 15 minutes. Make up the volume to 100 ml. Why ?

8. Starch indicator and pot. Iodate preparation Preparation of 0.01N Potassium Iodate (Mwt =214) Weigh accurately about 0.220 (0.365) g of KIO3 and dissolve in 100 ml distilled water Preparation of Starch indicator 1 gram of starch into 10 mL of distilled water, shake well, and pour into 100 mL of boiling , distilled water. Stir thoroughly and boil for a 1 minute . Leave to cool down. If the precipitate forms, decant the supernatant and use as the indicator solution. To make solution long lasting add a pinch of mercury iodide or salicylic acid, otherwise it can spoil after a few days.

9. procedure Take 10 ml of Potassium Iodate solution. Add 2 gm of Potassium Iodide and 5 ml of dilute H2SO4 (3N) keep it in dark for 10 minutes ( why ). Titrate with sod. Thiosulfate until pale yellow color appear. add 2 to 3 ml of starch indicator until the color turn to dark blue or black color. titrate with sodium thiosulfate using starch solution as indicator until the blue black colour is disappeared.

10. Procedure (cont.) Dark Conditions : Iodine can be sensitive to light, and keeping the solution in the dark prevents any photodecomposition of iodine, ensuring that you get accurate results. After the 10-minute incubation, you may notice a color change if starch is added, indicating the presence of iodine.

11. This experiment involves a classic iodine-starch reaction why each component is used and what happens : Potassium Iodate (KIO3): This serves as a source of iodate ions (IO3⁻), which can be reduced to iodine (I 2 ) under acidic conditions. Potassium Iodide (KI): This provides iodide ions (I⁻), which can react with the iodine produced to form a complex that is often used in starch tests. Dilute Sulfuric Acid (H2SO4): The acid creates an environment for the redox reaction to occur, facilitating the conversion of iodate to iodine.

12. Safety precautions Potassium iodate Oxidizer: Contact with combustible/organic material may cause fire or may intensify fire. Irritating to eyes, Irritating to skin Harmful if swallowed. Pot. Iodide Toxic to organs if swallowed (thyroid). May cause skin irritation, eye irritation, if inhaled may cause allergic bronchitis.

13. Demonstration

14. Thank you

15. Iodide ion I -1 Iodate ion IO 3 -1 Iodine I 2 Tridiodide I- 3