The following reagents are commonly used in the laboratory:
Acids : These include hydrochloric acid (HCl), perchlorics acid (HClO4), glacial acetic acid (CH3CO2H), sulphuric acid (H2SO4), phosphoric acid (H3PO4), sodium dihydrogen phosphate (NaH2PO4), lead nitrate [Pb(NO3)2], orthophosphoric acid, silver nitrate (AgNO3), boric acid (H3BO3), cupric acid, acetic acid (CH3CO2H), and ascorbic acid(C6H8O6).
Bases and Salts: These includes sodium hydroxide (NaOH), ammonium hydroxide (NH4OH), sodium chloride (NaCl), sodium hydogen orthophosphate, potassium hydroxide (KOH), Meyers reagent, Fehling I and Fehling II, saturated sodium chloride, potassium iodide (KI), alcoholic potassium hydroxide (alc. KOH), and ammonia (NH3).
Organic solvents: These include diethylether (C2H5OC2H5), ethanol(C2H5OH), chloroform(CHCl3), petroleum ether (mixture of pentane and hexane), Hexane (C6H14), acetone(CH3COCH3), formaldehyde(CH2O), acetonitrile (CH3CN), methanol (CH3OH), tetrahydrofuran, isopropanol (CH3CHOHCH3), dimethyl formamide, phenol, and alcohol.
Indicators: These include phenolphthalein, screened methyl red, methylene blue, methyl red, methyl orange, phenanthroline, cresol purple, ortho-ludine, crystal violet, xylenol orange, mordant black II, solochrome black T (Eriochrome black T), starch indicator, bromocresol green, bromomethylene blue, and resorcinol.
Buffers: These include sodium dihydrogen orthophosphate (NaH2PO4.2H2O), phosphate buffer, ammonium chloride buffer, sodium hexane sulphonic acid buffer.
Cleansing agents: Example is activated charcoal.
PREPARATION OF STOCK SOLUTIONS
Stock solutions are usually prepared for use in pharmaceutical chemistry and pharmaceutical control laboratories as follows:
Preparation of Buffer Solutions
Standard Buffer Solutions of pH 4, 7 and 10
Aim: To prepare standard Buffers of pH 4, 7 and 10.
Materials: 100-ml volumetric flask, disodium hydrogen orthophosphate buffer of pH 6.9 (equivalent to buffer pH 7.0) and distilled water.
Procedure: Buffer tablet of pH 4 was dissolved in a 100-ml volumetric flask with distilled water. It was shaken properly to dissolve, and was then made up to volume with more distilled water.
The same procedure was followed to prepare buffers 7 and 10.
Ammonium Chloride (NH4Cl) Buffer Solution of pH 10.8
Aim: To prepare ammonium chloride buffer solution of pH 10.8
Materials: Analytical balance, spatula, Ammonium chloride salt, 10M ammonia solution, 100-ml volumetric flask, and distilled water.
Procedure: 5.4g of ammonium chloride salt was weighed and dissolved in 20ml of distilled water. 35ml of 10M ammonia solution was added and diluted to the mark in a 100ml volumetric flask with distilled water.
Sodium Hexane Sulphonic Acid Buffer
Aim: To prepare sodium hexane sulphonic acid buffer.
Materials: Analytical balance, spatula, measuring cylinder, 2000-ml volumetric flask, sonicator, sodium hexane sulphonic acid salt, glacial acetic acid, and distilled water.
Procedure: 1.8822g of Sodium Hexane sulphonic acid salt was weighed into a 2litre volumetric flask. 1500ml of distilled water was added and shaken to dissolve. 20ml of glacial acetic acid was added and made up to the mark with distilled water. The solution was sonicated in a sonicator to remove air bubbles.
Preparation of Salt Solutions
24.818% Sodium ThiosulphatePentahydrate (Na2S2O3.5H2O) Solution
Aim: To prepare 24.818% sodium thiosulphatepentahydrate solution.
Materials: Analytical balance, spatula, Sodium Thiosulphate salt, 1000ml volumetric flask and Distilled water.
Procedure: 248.18g of the sodium thiosulphatepentahydrate salt was weighed and was transferred into a 1000ml volumetric flask, to which sufficient water was added. The flask was shaken properly to dissolve, and was made up to volume with more distilled water.
0.05M Iodine solution
Aim: To prepare 0.05M iodine solution.
Materials: Analytical balance, spatula, iodine salt, and distilled water.
Procedure: 3.1725g of iodine was weighed into a 500ml volumetric flask and dissolved with adequate amount of distilled water. The solution was made up to the mark with distilled water
0.1M Silver Nitrate (AgNO3) Solution
Aim: To prepare 0.1M silver nitrate solution.
Materials: Analytical balance, spatula, silver nitrate salt, and distilled water
17.0g of AgNO3 salt was weighed into a 1-litre volumetric flask and dissolved with adequate quantity of distilled water. The solution was made up to the 1-litre mark with distilled water.
Preparation of Acidic Solutions
25% Hydrochloric Acid (HCl) Solution
Aim: To prepare 25% hydrochloric acid solution.
Materials: Measuring cylinder, 100-ml volumetric flask, concentrated hydrochloric acid, and distilled water.
Procedure: 25ml of concentrated Hydrochloric acid was measured under the fume hood into a 100-ml volumetric flask containing a considerable amount of distilled water, more distilled water was added to make up to the mark.
1.0M Tetraoxosulphate (VI) Acid (H2SO4) Solution
Aim: To prepare 1.0M sulphuric acid solution.
Materials: Measuring cylinder, 500-ml volumetric flask, concentrated sulphuric acid (36.0%), and distilled water.
Procedure: 74ml of conc. H2SO4 was measured under the fume hood and was transferred into a 500ml volumetric flask containing some quantity of distilled water. The solution was then made up to 500ml with more distilled water.
Note: Acid was added to water and not water to acid.
The relation below was used to calculate the volume of concentrated H2SO4 to be measured in order to prepare 1.0M H2SO4 solution in a required amount:
V1=MCV10PD
Where:
M= Molar Mass of H2SO4 = 98g/mol
C= Concentration of H2SO4 to be prepared (Known) =1.0M
V= Volume of H2SO4 to be prepared (Known) =500ml
P= Percentage Purity or Assay (Usually found on the container’s label) =36.0%
D= Density of H2SO4 (Usually found on the container’s label) = 1.84g/cm3
V1=98×1.0×50010×36.0×1.84
V1=49000662.4
V1= 74ml
This is the method used to determine the volume of a stock solution required to prepare a given volume of known concentration of the solution.
Ascorbic acid solution
Aim: To prepare ascorbic acid solution.
Materials: Analytical balance, spatula, measuring cylinder, 500-ml volumetric flask, ascorbic acid powder, and dimethyl formamide.
Procedure: 0.5g of Ascorbic Acid powder was weighed and dissolved in 5ml of water. It was diluted to 500ml with dimethylformamide and wrapped with foil paper.
Note: preparation should be done in the dark.
Preparation of Alkaline Solutions
10M Ammonia solution
Given that the percentage purity and density of the stock ammonia solution are 25% and 0.903g/cm3, the required concentration was prepared using the dilution formula.
Aim: To prepare 10M ammonia solution.
Materials: Measuring cylinder, 100-ml volumetric flask, stock ammonia solution, and distilled water.
Procedure: 75ml of concentrated ammonia was measured under the fume cupboard using a measuring cylinder and was transferred into a 100ml volumetric flask. It was then diluted with distilled water to the 100ml mark.
50% Sodium Hydroxide (NaOH)
Aim: To prepare 50% sodium hydroxide solution.
Materials: Analytical balance, spatula, 500-ml volumetric flask, beakers, sodium hydroxide salt, and distilled water.
Procedure: 250g of NaOH crystals were weighed and dissolved in a beaker with adequate amount of distilled water which was placed under the influence of running water. The dissolved NaOH was transferred into a 500ml volumetric flask and made up to the mark with distilled water.
Preparation of 15% Tween-Water Stock Solution
Aim: To prepare 15% tween-water solution
Materials: Measuring cylinder, 1000-ml volumetric flask, tween solution, and distilled water.
Procedure: 150ml of tween solution was measured and added to 850ml of deionized or distilled water in a 1-litre volumetric flask. The resulting solution was swirled to mix.
Preparation of 70% Methanol-Tween Solution
Aim: To prepare 70% methanol-tween solution
Materials: Measuring cylinder, 1000-ml volumetric flask, 15% tween-water stock solution, and 100% methanol.
Procedure: 300ml of 15% tween-water stock solution was measured and added to 700ml of 100% methanol in a 1000-ml volumetric flask. The solution was swirled to mix.
Preparation of 1% starch indicator.
Aim: To prepare 1% starch indicator
Materials: Analytical balance, 1000-ml volumetric flask, spatula, starch, and hot water.
Procedure: 10g of starch was weighed and dissolved in hot water and made up to volume with hot water in 1000ml volumetric flask.
Preparation of Fehling I Solution
Aim: To prepare Fehling I solution.
Materials: Analytical balance, spatula, copper (II) sulphate salt, 1000-ml volumetric flask, glass rod, and distilled water.
Procedure: 69.278g of copper (II) sulphate (CuSO4) was weighed and was transferred into 1000-ml volumetric flask. Sufficient water was added, stirred and shaken properly to dissolve, after which it was made up to volume with more distilled water.
Preparation of Fehling II Solution
Aim: To prepare Fehling II solution.
Materials: Analytical balance, spatula, sodium hydroxide (NaOH) salt, sodium potassium tartarate salt, 1000-ml volumetric flask, glass rod, and distilled water.
Procedure: 100g of NaOH and 346g of sodium potassium tartarate salts were weighed and transferred into 1000-ml volumetric flask. Sufficient water was added, after which the mixture was stirred and shaken properly to dissolve. It was then made up to volume with more distilled water.
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