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Sodium Thiosulphate Lab Report

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Preparation of Standard Volumetric Solutions
1. 0.1N Sodium thiosulphate solution
Reagents: Sodium thiosulphate crystals, Potassium dichromate (primary standard NIST certified), Sulphuric acid, Potassium iodide , Starch Solution (1%): Weigh 1g of soluble starch and mix it with 100ml of boiled water.
Procedure
• Weigh 25 g of sodium thiosulphate crystals and transfer it in a 1000 ml volumetric flask.
• Dissolve it in minimum amount of distilled water and make up the volume to 1000 ml.
Standardization of the prepared Sodium thiosulphate solution as follows:
• Weigh 0.125 g of dry Potassium dichromate (K2Cr2O7) and transfer it into an iodine flask. Dissolve it in minimum amount of distilled water.
• Add 10 ml of Sulphuric acid and then 10 ml …show more content…

• Continue the titration until the colour changes sharply from blue to light green. Repeat the titration two more times.
• Calculate the normality of sodium thiosulphate solution on the basis of normality of potassium dichromate.

Observations and Calculations:
Normality of Sodium Thiosulphate (Na2S2O3) = Wt of K2Cr2O7 × 1000 Vol of 0.1 N Na2S2O3 solution used × 49.03 S. No. Weight of Potassium dichromate
(g) Volume of 0.1 N Sodium thiosuphate solution used
(ml) Normality of Na2S2O3 …show more content…

S. No. Wt of empty dish, W (g) wt of (sample + dish) before drying ,W1 (g) wt of (sample + dish) after drying ,W2 (g) Moisture % Average
1 73.5172 76.5891 76.2216 11.96%
11.66%
2 77.1345 79.3092 79.0619 11.37%

Result
The percentage of moisture content determined in Chana dal is 11.66% .

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EXPERIMENT 3

Aim: To determine the fat content in food sample by Soxhlet extraction method.

Introduction
The crude fat content can be conveniently determined in foods by extracting the dried and ground material with petroleum ether or diethyl ether in Soxhlet extraction apparatus.

Principle
Extraction of the crude fat is carried out either with petroleum ether or diethyl ether in a Soxhlet unit followed by volatilization of the solvent after extraction and determination of the mass of the residue.

Apparatus Required
Soxhlet apparatus

Reagents
Diethyl Ether -anhydrous or Petroleum ether (b.p. 60-80°C)

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