Tartaric Acid titration

Tartaric acid, H2C4H4O6, is a diprotic weak acid with a pK i of 3.0 and a pK 2 of 4.4. Suppose you have a sample of impure tartaric acid (%purity > 80) and that you plan to determine its purity by titrating with a solution of 0.1 M NaOH using a visual indicator to signal the end point. Describe how you would carry out the analysis, paying particular attention to how much sample you would use, the desired pH range over which you would like the visual indicator to operate, and how you would calculate the %w/w tartaric acid. 

The calcium salt of the principal product, d/-tartaric acid, crystallizes with four molecules of water, while the secondary product, meso-tartaric acid, forms a calcium salt which crystallizes with three molecules of water. The amount of sulfuric acid actually required may readily be calculated from the percentage of calcium found on analysis in the regular way or it may be estimated by igniting a sample, and titrating the residue with standard acid. 

An artificial fruit beverage contains 12.0 g of tartaric acid, H2C4H406, to achieve tartness. It is titrated with a basic solution that has a density of 1.045 g/cm3 and contains 5.00 mass percent KOH. What volume of the basic solution is required (One mole of tartaric acid reacts with two moles of hydroxide ion.)... 

With a knowledge of the pH at the stoichiometric point and also of the course of the neutralisation curve, it should be an easy matter to select the appropriate indicator for the titration of any diprotic acid for which K1/K2 is at least 104. For many diprotic acids, however, the two dissociation constants are too close together and it is not possible to differentiate between the two stages. If K 2 is not less than about 10 7, all the replaceable hydrogen may be titrated, e.g. sulphuric acid (primary stage — a strong acid), oxalic acid, malonic, succinic, and tartaric acids. 

A similar procedure may also be used for the determination of antimony(V), whilst antimony (III) may be determined like arsenic(III) by direct titration with standard iodine solution (Section 10.113), but in the antimony titration it is necessary to include some tartaric acid in the solution this acts as complexing agent and prevents precipitation of antimony as hydroxide or as basic salt in alkaline solution. On the whole, however, the most satisfactory method for determining antimony is by titration with potassium bromate (Section 10.133). 

The introduction of reversible redox indicators for the determination of arsenic(III) and antimony(III) has considerably simplified the procedure those at present available include 1-naphthoflavone, and p-ethoxychrysoidine. The addition of a little tartaric acid or potassium sodium tartrate is recommended when antimony(III) is titrated with bromate in the presence of the reversible... 

The effect of different ions upon the titration is similar to that given under iron(III) (Section 17.57). Iron(III) interferes (small amounts may be precipitated with sodium fluoride solution) tin(IV) should be masked with 20 per cent aqueous tartaric acid solution. The procedure may be employed for the determination of copper in brass, bronze, and bell metal without any previous separations except the removal of insoluble lead sulphate when present. 

In the indirect amperometric method [560], saturated uranyl zinc acetate solution is added to the sample containing 0.1-10 mg sodium. The solution is heated for 30 minutes at 100 °C to complete precipitation. The solution is filtered and the precipitate washed several times with 2 ml of the reagent and then five times with 99% ethanol saturated with sodium uranyl zinc acetate. The precipitate is dissolved and diluted to a known volume. To an aliquot containing up to 1.7 mg zinc, 1M tartaric acid (2-3 ml) and 3 M ammonium acetate (8-10 ml) are added and the pH adjusted to 7.5-8.0 with 2 M aqueous ammonia. The solution is diluted to 25 ml and an equal volume of ethanol added. It is titrated amperometrically with 0.01 M K4Fe(CN)6 using a platinum electrode. Uranium does not interfere with the determination of sodium. 

In contrast to aspirin itself, the U.S.P. monograph for aspirin tablets has undergone considerable changes. For some reason, U.S.P. does not use the ferric salt test for free salicylic acid, as does the British Pharmacopeia of 1973. Apparently, certain excipients such as citric and tartaric acid interfere with this reaction.77 Already in 1913, a double titration method was developed78 which was made an official method in 1926.79 This method was used as the assay method when the aspirin tablets monograph was introduced into U.S.P. XII in 1942. 

A solution of the calculated amount of tartaric acid is prepared in methanol (ca. 8 ml/g). Approximately V2 of the methanol to be used and 20% of the tartaric acid solution is added to the flask containing the LSD base. The flask is swirled and/or shaken until the solid material has dissolved (5-10 minutes) and the solution is then transferred into an Erlenmeyer flask. The balance of the methanol, in two portions, is used to complete the transfer. At this point the rest of the tartaric acid solution is added. It may be helpful to titrate the solution to an end-point pH of 5.3, since adding excess tartaric acid solution inhibits crystallization somewhat. However this is optional. If seed crystals are available, they should be added at this point. Crystallization should begin within a lh hour. The flask should then be refrigerated for 12-24 hours at 5-10° C and then for another 12 hours at -10 to -20° C. For 5 g of LSD base 1 g of tartaric acid in 7-8 ml methanol and an additional 17-18 ml of methanol are used. 

Procedure Place 2 g of previously dried and accurately weighed sample of tartaric acid in a conical flask. Dissolve it in 40 ml of DW, add a few drops of phenolphthalein indicator and titrate with standardized 1 N sodium hydroxide. Each millilitre of 1 N sodium hydroxide is equivalent to 75.04 mg of C4HgOg. 

Quantitative Determination. — Dissolve 1 gm. of tartaric acid in 50 cc. of water, and titrate with normal sodium hydroxide solution, using phenolphthalein as indicator. 

Total Acid. Simple titration procedures are used to determine total acidity. Problems arise because of the widely varying amounts of different acids in wines tartaric, malic, citric, lactic, succinic, acetic, etc. Different pKtt values for these acids make it impossible to predetermine easily the correct pH of the endpoint. Since a strong base is being used to titrate relatively weak acids, the endpoint will be greater than pH 7. In this country phenolphthalein (8.3) or cresol red (7.7) endpoints or a pH meter to 9.0 have been used (3, 6, 12, 76, 77) and the results are expressed as tartaric acid. The result at pH 7.7 X 1.05 approximately equals the result of titrating to pH 8.4. In Europe pH 7 is usually the endpoint, in France the results are expressed as sulfuric acid, and in Germany as tartaric or in milliequivalents (78). 

Tartaric Acid. Quantitative measures of total tartrate are useful in determining the amount of acid reduction required for high acid musts and in predicting the tartrate stability of finished wines. Three procedures may be used. Precipitation as calcium racemate is accurate (85), but the cost and unavailability of L-tartaric acid are prohibitive. Precipitation of tartaric acid as potassium bitartrate is the oldest procedure but is somewhat empirical because of the appreciable solubility of potassium bi-tartrate. Nevertheless, it is still an official AO AC method (3). The colorimetric metavanadate procedure is widely used (4, 6, 86, 87). Tanner and Sandoz (88) reported good correlation between their bitartrate procedure and Rebeleins rapid colorimetric method (87). Potentiometric titration in Me2CO after ion exchange was specific for tartaric acid (89). 

Alkali metal complexes may be analyzed for their metal content by simple acidimetric titration. Analysis for adduct (hydroxide) content is more involved, and entails the assumption that there can be no water of hydration attached to an alcoholate anion. The method involves first, dissolving the complex in anhydrous methanol, and then, treating the resulting solution with an appropriate anhydrous add, such as tartaric acid. The acid serves to convert any hydroxide ion into water (reaction S),... 

The use of ISEs with ion-selective membranes based on plasticized PVC, as well as glass pH electrodes, is limited to the analysis of aqueous solutions. On the other hand, sensors based on conducting polymer membranes are usually insoluble in organic solvents, which extends the range of possible applications. Electrosynthesized polypyrrole doped with calcion works as a Ca2+ sensor that can be applied as indicator electrode in the titration of Ca2+ with NaF in mixed solvents, such as water-methanol (1 1) and water-ethanol (1 1) [52], Another example is the use of polyaniline as indicator electrode in order to follow the acid-base precipitation titration of trimeprazine base with tartaric acid in isopropanol solution (see Procedure 5). 

Titration of trimeprazine base with tartaric acid in isopropanol solution using polyaniline as indicator electrode... 

Trimeprazine base-isopropanol solutions (0.2-1.4 M) were titrated with tartaric acid-isopropanol solutions (0.1-0.7 M) under simultaneous recording of the potential of the GC/PANI electrode vs. the Ag/AgCl/3 M KC1 reference electrode, as follows ... 

Add 0.1 M tartaric acid in the following portions 4x5 ml, 10 x 1 ml, 4x5 ml. Allow the potential of the GC/PANI electrode to stabilize between each addition. Recording of the titration curve in this manner takes ca. 2 h. An example of the titration curve is shown in Fig. 5.2. The occurrence of a potential maximum at 5-10 ml and the minimum at 15 ml tartaric acid indicates where precipitation of trimeprazine tartrate starts. The increasing potential around 25 ml tartaric acid indicates the equivalence point. Titration of 1.4 M trimeprazine base with 0.7M tartaric acid results in a larger potential change at the equivalence point, as can be seen in Fig. 5.3. 

After the titration, the GC/PANI electrode is rinsed in isopropanol and conditioned in 0.01 M tartaric acid-isopropanol. 

Fig. 5.2. Potential of three identical GC/PANI electrodes recorded during the titration of 0.2 M trimeprazine base (V = 25 ml) with 0.1 M tartaric acid.

The titration of trimeprazine base with tartaric acid in isopropanol solution results in protonation of trimeprazine and precipitation of trimeprazine tartrate, according to the following schematic reaction (proton transfer not shown) ... 

In warmer vintages in the North Coast, grapes, especially riper grapes at 23°-24° Brix, may be low in titratable acidity. Desirable levels of acidity in white juice prior to fermentation range from 0.7 to 1.0 g/100 mL, depending on final wine composition and wine style desired. Tartaric acid is used most commonly for acidulation and often is added to juice prior to fermentation. Malic acid and citric acid also are used for acidulation. 

The gel in this case is formed containing sodium tartrate and sodium hydrogen tartrate. About SO mL of 0.5 M tartaric acid is titrated with 0.S M sodium metasilicate to a pH of 4. After titration the solution is placed into 50-mL test tubes and allowed to set. About 30 mL of solution is added to each tube. The tubes should set for 1 or 2 days. Fifteen milliliters of a 0.S M CaCl2 solution is then added above the gel in each tube and the tubes are lightly stoppered. They are then placed in a controlled-temperature bath at 40°C in the dark. Close temperature control is not needed. The reaction time is about 2 weeks. 

Oxyacids, like citric or tartaric acids, and polyols, like saccharose are also used, mainly as masking agents, in qualitative analysis. The action of some specific reagents, like oc-a -bipyridyl for iron(II) and dimethylglyoxime for nickel(II), is also based on the formation of chelate complexes. In quantitative analysis the formation of chelates is frequently utilized (complexometric titrations). ... 

Titratable acidity is expressed in tartaric acid equivalents, volatile acidity is expressed in acetic acid equivalents... 

Pipcric acid is insoluble in water, but soluble in aqueous NaOH and aqueous NaHC03. Titration gives an equivalent weight of 215 6. It reacts readily with Br2/CCl4, without evolution of HBr, to yield a compound of formula Ci2Hio04Br4. Careful oxidation of piperic acid yields piperonylic acid, C8H6O4, and tartaric acid, HOOCCHOHCHOHCOOH. 

A 50.00-ntL sample of a white dinner wine required 21.48 mL of 0.03776 M NaOH to achieve a phenolphthalein end point. Express the acidity of the wine in terms of grams of tartaric acid (H2C4H4O15, 150.09 g/mol) per 100 mL. (Assume that both acidic protons of the compound ai e titrated.)... 

Tartaric acid is often added to artificial fruit drinks to increase tartness. A sample of a certain beverage contains 1.00 g of tartaric acid, H2C4H4O6. The beverage is titrated with O.lOOMNaOH. Assuming no other acids are present, how many milliliters of base are required to neutralize the tartaric acid ... 

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