Water titrations

I) The solution may be analysed approximately as follows. Remove 25 ml. of the ether solution and run it into 25 ml. of water contained in a small separatory funnel shake. Run off the aqueous layer into a 250 ml. conical flask and extract the ether layer with two 25 ml. portions of water. Titrate the combined aqueous extracts with 0 - IN sulphuric acid, using methyl red as indicator. 

A 0.5I3I-g sample containing KBr is dissolved in 50 ml of distilled water. Titrating with 0.04614 M AgN03 requires 25.13 ml to reach the Mohr end point. A blank titration requires 0.65 ml to reach the same end point. Report the %w/w KBr in the sample. 

A commercial silver alloy in the form of wire or foil is suitable for this determination. Clean the alloy with emery cloth and weigh it accurately. Place it in a 250 mL conical flask, add 5 mL water and 10 mL concentrated nitric acid place a funnel in the mouth of the flask to avoid mechanical loss. Warm the flask gently until the alloy has dissolved. Add a little water and boil for 5 minutes in order to expel oxides of nitrogen. Transfer the cold solution quantitatively to a 100 mL graduated flask and make up to the mark with distilled water. Titrate 25 mL portions of the solution with standard 0.1 M thiocyanate. 

Suppose that 4.25 g of an unknown monoprotic weak acid, HA, is dissolved in water. Titration of the solution with 0.350 M NaOH(aq) required 52.0 mL to reach the stoichiometric point. After the addition of 26.0 mL, the pH of the solution was found to be 3.82. (a) What is the molar mass of the acid (b) What is the value of pK, for the acid ... 

C04-0157. As a final examination in the general chemistry laboratory, a student was asked to determine the mass of Ca (0H)2 that dissolves in 1.000 L water. Using a published procedure, the student did the following (1) About 1.5 mL of concentrated HCl (12 M) was added to 750 mL of distilled water. (2) A solution of KOH was prepared by adding approximately 1.37 g KOH to 1.0 L distilled water. (3) A sample of potassium hydrogen phthalate (185.9 mg) was dissolved in 100 mL of distilled water. Titration with the KOH solution required 25.67 mL to reach the stoichiometric point. (4) A 50.00-mL sample of the HCl solution prepared in step 1 was titrated with the KOH solution. The titration required 34.02 mL of titrant to reach the stoichiometric point. (5) The student was given a 25.00-mL sample of a saturated solution of Ca (0H)2 for analysis. Titration with the HCl solution required 29.28 mL to reach the stoichiometric point. How many grams of calcium hydroxide dissolve in 1.00 L of water ... 

Fig. 3.86. Coulometric Karl Fischer water titration (Courtesy of Metrohm). 

Although the DL 40 was capable of performing Karl Fischer water titrations and Mettler developed a separate microprocessor-controlled push-button operated DL 18 KF titrator, they also introduced as an all-purpose apparatus the improved DL 40 RC (see Fig. 5.11) with a dual titration head and with a modified software program to handle the new two-component titrants for Karl Fischer titration (see pp. 204-205). The instrument can also be expanded into an automatic series titrator by connecting the RT 40 sample transport for 16 samples and storage of 50 sample weights from a connected balance this series routine can be interrupted at any time after completion of the titration in progress. 

The British Pharmacopoeia [10] and the European Pharmacopoeia [11] also recommend a potentiometric method for valproic acid. Dissolve 0.100 g in 25 mL of alcohol. Add 2 mL of water. Titrate with 0.1 M sodium hydroxide determining the endpoint potentiometrically. Each 1 mL of 0.1 M sodium hydroxide is equivalent to 14.42 mg of C8H1602. 

The iodine then reacts with the water that is present. The amount of water titrated is proportional to the total current (according to Faraday s law) used in generating the iodine necessary to react with the water. One mole of iodine reacts quantitatively with 1 mol of water. As a result, 1 mg of water is equivalent to 10.71 C. Based on this principle, the water content of the sample can be determined by the quantity of current that flows during the electrolysis. For this reason, the coulometric method is considered an absolute technique, and no standardization of the reagents is required. 

The stop buffer comprises 0.2 M Na2C03/glycine pH 10.5 Dissolve 21.2 g Na2C03 in 400 ml water. Dissolve 3.75 g glycine in 100 ml water. Titrate 400 ml of the Na2C03 solution with the glycine solution to pH 10.5. Add water to 1 L. This stop buffer is used in all assays unless indicated otherwise. When assays are adapted to microtiter plates, detergent (0.025% w/v Triton X-100) should be present in the stop buffers in order to minimize meniscus effects. 

Buffer add 6 ml ammoniac (25%, Merck) to 900 ml HPLC-water, titrate with formic acid 98-100% Suprapur (Merck) to pH 4.4 and fill up to 1 1 to obtain 80 mM ammonium formate (pH 4.4). 

The Fajans titration of Cl with Ag+ convincingly demonstrates indicator end points in precipitation titrations. Dissolve 0.5 g of NaCl plus 0.15 g of dextrin in 400 mL of water. The purpose of the dextrin is to retard coagulation of the AgCl precipitate. Add 1 mL of dichlorofluorescein indicator solution containing either 1 mg/mL of dichlorofluorescein in 95% aqueous ethanol or 1 mg/mL of the sodium salt in water. Titrate the NaCl solution... 

Calculation of water of crystallisation Solubility of salts in water Titration Checklist... 

H.L. Greenwald, G.L. Brown and M.N. Fineman, Determination of the hydrophile-lipophile character of surface active agents and oils by a water titration, Anal. Chem. 28 (1956) 1693-1697. 

Fig. 6. Potentiometric titration cuves of dibiasic 17 (V-) 22 (A) 35 (O) and 48 ( ) and of partially quatemized poly[thio-l-N,N-dimethyl-aminomethyl)ethylene] (O) in water [titrating reagent, 1 M HC1)]. The numbers refer to the percent of quaternized nitrogens...

Solvents. Methylene chloride (Hooker, Dow Chemical, Stauffer, DuPont, Eastman, and Fisher) from most suppliers was satisfactory. After drying over sieves (Linde, Type 3A), the solvent generally contained <10 p.p.m. water, by Karl Fisher water titration. 

Add 2 g of sodium fluoride, boil the mixture for 2 to 5 min, and cool in a stream of running water. Titrate the EDTA (which is released by fluoride from its aluminum complex) with 0.01 M Zinc Sulfate to the same transitory yellow-brown or pink endpoint as described above. 

Ethyl Formate (Acidity as Formic Acid) Transfer about 5 g of sample, accurately weighed, into a glass-stoppered flask containing a solution of 500 mg of potassium iodate and 2 g of potassium iodide in 50 mL of water. Titrate the liberated iodine with 0.1 A sodium thiosulfate, using starch TS as the indicator. Each milliliter of 0.1 N sodium thiosulfate is equivalent to 4.603 mg of CH2O2. 

Allow the sample solution to stand, agitating it occasionally, for exactly 1 min, and immediately add 30 mL of water. Titrate with 0.1 A sodium thiosulfate solution, adding the solution gradually while constantly agitating until the yellow iodine color has almost disappeared. Add 0.5 mL of a 10% sodium lauryl sulfate (SDS) solution, and then add approximately 0.5 mL of Starch Indicator Solution. Continue the titration while constantly agitating, especially near the endpoint to liberate all of the iodine from the solvent layer. Add 0.1 A thiosulfate solution dropwise until the blue color just disappears. If the titration is less than 0.5 mL using 0.1 A sodium thiosulfate, repeat the determination using 0.01 A sodium thiosulfate. Conduct a blank determination, and make any necessary correction. Calculate the peroxide value by the formula... 

M Tris chloride, pH 8.8—Dissolve 91 g of Tris (tris-hydroxytnethyl-aminomethane) free base in about 375 ml of distilled water. Titrate the solution to pH 8.8 with concentrated HC1 and dilute to 500 ml with distilled water. 

M Tris chloride buffer, pH 9.2—Dissolve 6.05 g Tris free base in distilled water, titrate to pH 9.2 with... 

Sterile 0.1 M EGTA, pH 7.9—Dissolve 1.9 g of EGTA (ethylene glycol-bis(/3-aminoethyl ether) N, N, N, N -tetraacetic acid) in 35 ml of distilled water, titrate to pH 7.9 with 1 N NaOH, and dilute to 50 ml final volume with distilled water. Autoclave in a capped test tube (20 min at 105-110°C) and cool. 

Scatchard plot analysis of data for river water titrations was conducted for values of [Gujot] 2 10 H. This was done because of apparent non-ideal electrode behavior at [Cujot]... 

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