STANDARDISATION OF 0.1N SODIUM THIOSULPHATE
Laboratory for the third stage
Organic Pharmaceutical Chemistry
Prepared By Dr. Ali Hussein Mustafa AL-OBAIDI
College of Pharmacy -Tikrit University / 2020
Chemical Structure Of Sodium Thiosulphate
Aim:
To determine the normality of given sample of sodium thiosulphate (Na2S2O3) .
Reference:
1. Record in the GESTIS Substance Database of the Institute for Occupational Safety and Health 2. ^ Jump up to:a b c d e Barbera JJ, Metzger A, Wolf M (2012). "Sulfites, Thiosulfates, and Dithionites". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley- VCH. doi:10.1002/14356007.a25_477. ISBN 9783527306732. 3. ^ Jump up to:a b c Stuart MC, Kouimtzi M, Hill SR, eds. (2006). WHO Model Formulary 2008 (PDF). Switzerland: WHO. p. 66. ISBN 9789241547659. Retrieved 8 Jan 2017. 4. ^ World Health Organization (2019). World Health Organization model list of essential medicines: 21st list 2019. Geneva: World Health Organization. hdl:10665/325771. WHO/MVP/EMP/IAU/2019.06. License: CC BY-NC-SA 3.0 IGO. 5. ^ Sunenshine PJ, Schwartz RA, Janniger CK (2002). "Tinea versicolor". Int. J. Dermatol. 37 (9): 648– 55. doi:10.1046/j.1365-4362.1998.00441.x. 6. ^ Auriemma M, Carbone A, Di Liberato L, et al. (2011). "Treatment of Cutaneous Calciphylaxis with Sodium Thiosulfate: Two Case Reports and a Review of the Literature". Am. J. Clin. Dermatol. 12 (5): 339– 46. doi:10.2165/11587060-000000000-00000. PMID 21834598. 7. ^ Dickey DT, Wu YJ, Muldoon LL, et al. (2005). "Protection against Cisplatin-Induced Toxicities by N- Acetylcysteine and Sodium Thiosulfate as Assessed at the Molecular, Cellular, and in Vivo Levels". J. Pharmacol. Exp. Ther. 314 (3): 1052–8. doi:10.1124/jpet.105.087601. PMID 15951398.
About Sodium thiosulfate
Sodium thiosulfate (sodium thiosulphate) is an inorganic compound with the formula
Na2S2O3.xH2O. Typically it is available as the white or colorless pentahydrate, Na2S2O3·5H2O. The solid is an efflorescent (loses water readily) crystalline substance that dissolves well in water.[2]
Sodium thiosulfate is used in gold mining, water treatment, analytical chemistry, the development of silver-based photographic film and prints, and medicine. The medical uses of sodium thiosulfate include treatment of cyanide poisoning and pityriasis.[3] It is on the world health organization's List of Essential Medicines, the safest and most effective medicines needed in a health system.[4]
Medical uses: Main article: Sodium thiosulfate (medical use) Sodium thiosulfate is used in the treatment of cyanide poisoning.[3] Other uses include topical treatment of ringworm and tinea versicolor,[3][5] and treating some side effects of hemodialysis[6] and chemotherapy.[7]
Requirements: Apparatus : Burette, Volumetric flask, Pipette. Reagents : 0.1 N sodium thiosulphate, Potassium iodate, Potassium iodide
PRINCIPLE: The principle of standardization of sodium thiosulphate is based on redox iodometric titration with potassium iodate as primary standard. Potassium iodate a strong oxidizing agent is treated with excess potassium iodide in acidic media which liberates iodine which is back titrated with sodium thioslphate. Uniformity of reactions between iodine and sodium thiosulphate forms basis for utilizing the standard solution of iodine in the analysis of sodium thiosulphate and use of sodium thiosulphate in the analysis of iodine. Starch indicator is used as indicator showing disappearance of blue color.
KIO3 + 5KI + 3H2SO4 → 3K2SO4 + 3H2O
I2 + 2Na2S2O3 → 2NaI + Na2S4O6 Procedure:
Preparation of 0.1N Sodium thiosulphate
Dissolve 24.8g of sodium thiosulphate pentahydrate(Na2S2O3.5H2O) in 800 ml of freshly boiled and cooled water and mix thoroughly by shaking for approximately 15 minutes. Make up the volume to 1000 ml.
Preparation of 0.1N Potassium Iodate
Weigh accurately about 356 mg of KIO3 and dissolve in 100 ml distilled water
Preparation of Starch indicator
Take 1 gm of soluble starch and triturate with 5 ml of water and add it to 100 ml of boiling water containing 10 mg of mercuric iodide with continous stirring
Standardisation of 0.1N sodium thiosulphate
Take 10 ml of Potassium Iodate solution .Add 2 gm of Potassium Iodide and 5 ml of dilute H2SO4 ,keep it in dark for 10 minutes, add 2 to 3 drops of starch indicator and titrate with sodium thiosulphate using starch solution as indicator until the blue colour is disappeared.
N 1V1 = N 2V 2 N 2 = N 1V 1 V 2
Report: The strength of the given solution of sodium thiosulphate is ……… The process steps for the experiment are illustrated in pictures:-
1- Prepare the standard solutions and the Potassium Iodate solution in laboratory.
2- Titration
3- Calculate the experiment:
N 1V1 = N 2V 2
N 2 = N 1V 1 V 2
4- Writing a report on the experiment.