Standard flask

Average boiling point defined as the mean of the temperatures in °C at which 10%, 20%,...90% by volume distills in a standard flask distillation. 

Four 10 ml. aliquots of the standard solution are pipetted into separate 25 ml. volumetric flasks, two are labelled standard and the others blank. One ml. of 0.5N H2S04 is added to the blank flasks and they are allowed to stand after mixing at room temperature for 60 minutes 1 5 minutes. Two ml. of purified water are added to the standard flasks. At the end of this time, 1.0 ml. of 0.IN NaOH is added to the blank flasks and their contents swirled... 

To determine the silver composition of an alloy, a piece of alloy weighing 10-48g was dissolved in nitric acid and the resulting solution was diluted to 1-00 litre in a standard flask. 0-20 moll hydrochloric acid was added to 100-0 cm of this solution until precipitation of silver(l) chloride was complete. 

In an experiment to determine the percentage of nickel In hydrated nlckel(ll) sulfate, 2-63 g of the nlckel(ll) sulfate were weighed accurately, dissolved In water and diluted to 100 cm in a standard flask. A 20-0 cm volume of this solution was pipetted Into a conical flask along with an indicator solution. This solution was titrated against a 0-100 mol fi EDTA solution until the end-point was observed. The titrations were repeated until concordant results were obtained. 

A 10-0 cm3 volume of a liquid drain cleaner containing sodium hydroxide was diluted to 250 cm3 g standard flask. Samples of this diluted solution with volumes of 25-0 cm3 ere pipetted into a conical flask and titrated against a 0-220 mol h sulfuric acid solution. The average of the concordant titres was 17-8 cm3. Calculate the mass of sodium hydroxide in one litre of the drain cleaner. 

A 1-50 g mass of aspirin was hydrolysed with 25-0 cm of 1-00 mol NaOH solution. After the hydrolysis was complete, the reaction mixture was transferred, with rinsings, to a 250 cm standard flask and made up to the graduation mark with distilled water. The solution was mixed thoroughly and 25-0 cm was pipetted Into a conical flask, along with a few drops of phenolphthalein Indicator. This was titrated with 0-0500 mol sulfuric add solution until the end-point of the titration was Indicated by the colour change from pink to colourless. The titrations were repeated until concordant results were obtained. 

In an experiment to determine the percentage by mass of manganese in a steel paper clip, it is necessary to prepare various concentrations of standard potassium permanganate solutions. You will learn more about this experiment on p. 88. A standard 0 0010 mol h solution of potassium permanganate is often used as a stock solution in this experiment. Dilutions of the stock solution are prepared by accurately transferring a known volume of the stock solution, using a pipette or a burette, into a volumetric flask (standard flask). The flask is then carefully filled to the graduation mark with deionised water. 

In the 250 cm standard flask, there must have been 0-007832 X 10 = 0-07832 mol of NaOH. 

The submitter used a special apparatus suitable for the rapid evaporation of water under reduced pressure. The checkers used standard flasks. 

Into a standard flask (see illustration below), equipped with motorized stirrer or other stirring means, addition funnel, and thermometer, place 45 milliliters (1.5 fluid oz.) of ice water. Thereafter, slowly and carefully add in 75 milliliters (4 fluid oz.) of 98% sulfuric acid. Then place this acid mixture into an ice bath, and chill to about 0 Celsius. Afterwards, place 75 milliliters (4 fluid oz.) of... 

Always clean up the lab and all equipment after use. Dispose of the contents of the waste beaker in the container designated by your teacher. Also pour the contents of the color-standard flask into this container. Wash your hands thoroughly after cleaning up the area and equipment. 

When preparing standard working solutions it is best to conform with the rule of tenfold dilution and using adequately accurate pipettes and standard flasks (e.g., a 10 ml pipette and a 100 ml flask. From a solution of concentration 1 mg/ml one obtains a solution of 0.1 mg/ml and, in turn, 10 pg/ml. 

The analytical procedures are presented in a unified form. The maximum quantities given for a corresponding analyte refer to a 25 ml standard flask and a cuvette of thickness 1 cm. The quantities of reagents should be changed if the coloured solutions are placed in a flask of capacity 10 ml or 50 ml, and a cuvette of other thickness is applied. 

Standard aluminium solution 1 mg/ml. Dissolve 17.5900 g of KA1(S04)212H2O in water containing 5 ml of cone. H2SO4 dilute the solution to 1 litre with water in a standard flask. Working solution is given by suitable dilution of stock solution with -0.01 M H2SO4. EDTA (disodium salt), 5% solution. 

Transfer the solution to a separating funnel, and extract the aluminium with two portions of the chloroform-oxine solution. Wash the combined extracts with two portions of water and make the solution up to the mark with the oxine solution in a 25 ml standard flask. Measure the absorbance of the extract at 390 nm, using as reference a reagent blank solution. 

To a solution in dilute HCl, containing not more than 10 pg of Al, add 1 ml of ascorbic acid solution, and adjust the pH of the solution with ammonia to 2. After 5 min, dilute the solution with water to 15 ml, and add 2.5 ml of CAS solution and 1 ml of 20% sodium acetate solution. Adjust the pH of the solution with ammonia to 6.0 0.2, dilute with water to 25 ml in a standard flask, and measure the absorbance of the solution at 545 nm, against a reagent blank as reference. 

Place a sample solution in dilute HCl (pH 1-2, 10-15 ml), containing not more than 5 pg Al, in a small beaker and add 10 mg of ascorbic acid. After 5 min add -2 ml of CAS solution, and adjust the pH to 5.3 0.2 with dilute ammonia solution. Dilute to volume in a 25 ml standard flask, mix, and measure the absorbance of the solution at 620 nm vs. a reagent blank solution. 

Determination of Sb. To the separating funnel with the ether solution of the antimony(V) chloride complex add 3 ml of the RB solution and shake. Transfer the coloured ether extract to a 25 ml standard flask, add DIPE to the mark, mix, and measure the absorbance at 552 nm using the solvent as a reference. 

Standard antimony solution 1 mg/ml. The solution may be prepared either from potassium antimonyl tartrate (Section 7.2.1) or in the following manner. Dissolve 0.1000 g of powdered antimony metal in 25 ml of cone. H2SO4. Dilute the cooled solution with water while stirring, cool, and make up to 100 ml in a standard flask. Working solutions are obtained by suitable dilution of the stock solution with 0.5 M H2SO4. 

Determination of As. To the aqueous phase, add 2 ml of cone. HNO3, stir, and evaporate the solution almost to dryness. Add 25 ml of molybdate reagent, stir well, and place the beaker in a boiling water-bath for 10 min. After cooling, transfer the solution to a separating funnel and extract the As-Mo blue with 2 portions (e.g. 10 ml) of butyl alcohol. Make up the blue extract to the mark in a 25-ml standard flask with the solvent, and measure the absorbance at 730 nm, using the solvent as reference. 

Standard beryllium solution 1 mg/ml. Dissolve 1.9640 g of BeS04.H20 in water containing 1 ml of cone. HCl, and dilute the solution with water to volume in a 100-ml standard flask... 

Standard bismuth solution Img/ml. Dissolve 2.3210 g of Bi(N03)3.5H20 in 100 ml of HNO3 (1 +3), and dilute the solution to volume with water, in a 1-litre standard flask. Working solutions are obtained by diluting the stock solution with O.OIM HNO3. 

Any Cu, Ag, Au, Pt, Pd, or Hg present in the sample should be removed by extraction with dithizone at pH 0.5-1.0. Adjust the pH of the sample solution, containing not more than 40 pg of Bi, with ammonia to pH 3.1 0.1. Extract Bi with several aliquots of the dithizone solution in CCI4 (1 ml of 0.001% H2DZ solution is equivalent to 2.7 pg of Bi). Wash the combined extracts by shaking successively with the wash solution, water, and then with a solution containing 3 drops of the buffer solution (pH 9.5) and 3 drops of 10% KCN solution per 10 ml of water. Finally wash the extract with water, and dilute to volume in a 25-ml or smaller standard flask with CCI4. Measure the absorbance of the extract at 490 nm, using the solvent or a blank solution as reference. 

Place 2.5 ml of acidic solution (-4 M H2SO4), containing not more than 25 pg of B, in a 25-ml standard flask. Add 5 drops of cone. HCl, 12.5 ml of cone. H2SO4, and carmine solution up to the mark. Mix the solution thoroughly and set aside for 1 h. Measure the absorbance of the solution at 650 nm, using a blank solution as reference. 

To a 100-ml separating funnel, add sample solution containing not more than 2.5 pg of B, then 2.5 ml of 10% NaF solution, and enough H2SO4 to give, finally, 8 ml of the solution, at concentration of about 0.4 M. After 30 min, add 40 ml of water, 10 ml of the MB solution, and shake the solution with two 10-ml portions of 1,2-dichloroethane (shaking time 1 min). Dilute the clear extract to volume with solvent in a 25-ml standard flask, mix well, and measure the absorbance of the solution at 665 nm, using the blank solution as a reference. 

Place an approximately neutral sample solution ( 12 ml), eontaining not more than 100 pg of Bf, in a 25-ml standard flask, add 4 ml of the borate buffer, 1 ml of the hypochlorite solution, and shake for 2 min. Add 1.0 ml of the Phenol Red solution, stir well, and let the solution stand for 4 min. Add 1.2 ml of the arsenite solution and 4 ml of the acetate buffer, and dilute to the mark with water. Measure the absorbance of the solution at 580 nm against a blank solution. 

Determination of Cd. Re-extract Cd from the extract obtained above by shaking (30 s) with 5 ml of the ammonia buffer, and then with 5 ml of water. To these aqueous solutions (in a 25-ml standard flask) containing not more than 15 pg of Cd, add 10 ml of ethanol, 2 ml of 5-Br-PADAP solution, dilute with water to the mark, mix well, and measure the absorbance of the solution at 556 nm vj. a reagent blank solution. 

Extraction of Ca with Azo-azoxy BN. Add sufficient 5M NaOH to the sample solution to make the NaOH concentration 0.5-1 M. Shake the solution for 1 min with the solution of Azo-azoxy BN. Strip calcium from the extract with a small volume of 1M hydrochloric acid. Determination of Ca. The sample solution should contain not more than 30 pg of Ca, and be free from ammonium salts and Analytical Group I-III metals (to mask small amounts of these metals, add 10 mg each of KCN and Na2S. Neutralize the sample solution (to pH 7-8) with NaOH or HCl, and add 20 mg of Na2S04. Add 12 ml of the GBHA solution and 1 ml of 1 M NaOH, and dilute the solution with water to the mark in a 25-ml standard flask. After 10 min, measure the absorbance of the solution at 516 nm against a blank solution. 

To the sample solution containing not more than 15 pg of Ca, add 2.5 ml of Chlorophosphonazo III solution, and water to -20 ml. Neutralize with ammonia to pH about 7, and add 1 ml of buffer solution. Transfer the solution to a 25-ml standard flask, dilute to volume with water, and mix well. After 15 min, measure the absorbanee of the solution at 668 nm v. a blank solution. 

Place the alkaline solution (about 10 ml) containing not more than 10 pg of CN in a 25-ml standard flask. Acidify the solution with glacial acetic acid and add 1 ml in excess. Immediately add 1 ml of bromine water. Mix the solution thoroughly, and let it stand for 10 min with occasional shaking. Add a 1.5% solution of sodium arsenite dropwise to reduce the excess of bromine, then 2-3 drops more. Add 5 ml of the benzidine-pyridine reagent, and stir the solution. After 30 sec, add 5 ml of ethanol, make up to the mark with water, and stir well. After 15 min, measure the absorbance of the solution at 530 nm against a reagent blank. 

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