Titrating the effluents

The titration must be done with alcoholic acid or alkali, and is best done potentiometrically with an autotitrator. Next best is manual potentiomet-ric titration, but it is satisfactory to use indicators, methyl orange or bromophenol blue for the low-pH end-point and phenolphthalein for the high-pH end-point. The information obtained is often a useful crosscheck on the mass balance in the analysis of an unknown, but it can also help in the analysis of WW amphoterics, which contain appreciable amounts of non-surfactant weak acids and bases. 

If any constituent of the acid effluent is acid-labile, or if any constituent of the alkaline effluent is alkali-labile, collect the effluent in a measured excess of alkali in the first case or a measured excess of acid in the second 

Effluents should be kept after titration for analysis of whatever surfactants they contain. 

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Fill a 250 mL separatory funnel with ca 0.25M sodium sulphate solution. Allow this solution to drip into the column at a rate of about 2 mL per minute, and collect the effluent in a 500 mL conical flask. When all the solution has passed through the column, titrate the effluent with standard 0.1 M sodium hydroxide using phenolphthalein as indicator. 

A 0.3126-g sample of pure KCl was passed through a cation-exchange column in the acid form. If 41.63 ml of a NaOH solution was required to titrate the effluent to the methyl red end point, what was the molarity of the NaOH ... 

For accurate results, it is advisable to control the surfactant adsorption performing a titration. The effluent leaving the column is collected until the detector response reaches a plateau corresponding to the absorbance value of the initial surfactant solution. The surfactant concentration in die collected effluent is determined by titration. The missing surfactant mass is adsorbed on the stationary phase in the column. The mass obtained by titration should corroborate the one obtained using the breakthrough volume. 

Titrate the effluent obtained at step 4 with the same titrant. 

Titrate the effluent from the cation-exchange column potentiometrically with ethanolic 0.1 M sodium hydroxide through two points of inflection at pHs below and above 7. 

As a corollary to the above it should be pointed out that the exchange is in some instances stoichiometric and therefore the amount of cation in solution can be estimated by passage through a hydrogen exchanger as above and subsequent titration of the acid in the effluent. 

Theory. The anion exchange resin, originally in the chloride form, is converted into the nitrate form by washing with sodium nitrate solution. A concentrated solution of the chloride and bromide mixture is introduced at the top of the column. The halide ions exchange rapidly with the nitrate ions in the resin, forming a band at the top of the column. Chloride ion is more rapidly eluted from this band than bromide ion by sodium nitrate solution, so that a separation is possible. The progress of elution of the halides is followed by titrating fractions of the effluents with standard silver nitrate solution. 

Weigh out accurately about 0.10 g of analytical grade sodium chloride and about 0.20 g of potassium bromide, dissolve the mixture in about 2.0 mL of water and transfer quantitatively to the top of the column with the aid of 0.3 M sodium nitrate. Pass 0.3 M sodium nitrate through the column at a flow rate of about 1 mL per minute and collect the effluent in 10 mL fractions. Transfer each fraction in turn to a conical flask, dilute with an equal volume of water, add 2 drops of 0.2M potassium chromate solution and titrate with standard 0.02M silver nitrate. 

Dissolve 20 g of tetra-n-butylammonium iodide in 100 mL of dry methanol and pass this solution through the column at a rate of about 5 mL min - L the effluent must be collected in a vessel fitted with a Carbosorb guard tube to protect it from atmospheric carbon dioxide. Then pass 200 mL of dry methanol through the column. Standardise the methanolic solution by carrying out a potentiometric titration of an accurately weighed portion (about 0.3 g) of benzoic acid. Calculate the molarity of the solution and add sufficient dry methanol to make it approximately 0.1M. 

As we saw in Section L, titration involves the addition of a solution, called the titrant, from a buret to a flask containing the sample, called the analyte. For example, if an environmental chemist is monitoring acid mine drainage and needs to know the concentration of acid in the water, a sample of the effluent from the mine would be the analyte and a solution of base of known concentration would be the titrant. At the stoichiometric point, the amount of OH " (or 11,0 ) added as titrant is equal to the amount of H30+ (or OH-) initially present in the analyte. The success of the technique depends on our ability to detect this point. We use the techniques in this chapter to identify the roles of different species in determining the pH and to select the appropriate indicator for a titration. 

In addition to the analysis of the thermal stability of the perchloric acid organic reaction media mixtures, a procedure was worked out to determine the fate of the perchloric acid by chlorine analysis of the batch, effluent streams, etc. Preliminary analyses on selected process samples showed no tendency for perchloric acid to concentrate in recycle material and therefore build up in the reactor. A total of less than 1% of the initial charge of perchloric acid (total chlorides calculated as perchloric acid) was found in the combined recovered acid-ester and olefin fractions. Less than 1 % of the initial charge of perchloric acid was found in the finished ester. The analytical method used was an oxygen bomb decomposition, followed by titration of chlorides with 0.0liV silver nitrate, using a recording automatic titrator. The eventual fate of the perchloric acid catalyst was... 

For serum replacement (6), the latex is confined in a cell with a uniform-pore-size Nuclepore filtration membrane. Distilled, deionized water is pumped through the latex until the conductance of the effluent stream is about the same as that of the distilled, deionized water. This serum replacement removes the adsorbed emulsifier and solute electrolyte quantitatively and allows recovery of the serum in a form suitable for further analysis however, it does not+replace the Na+ and K counterions of the surface groups with Vl ions. To do this, dilute hydrochloric acid (ca. 10 N) is pumped through the latex, followed by distilled, deionized water to remove the excess acid. The latex is then titrated conductometrically to determine the surface charge. 

Effluent-gas Analysis.4 This method of analysis gives an estimate both of the chlorine (IV) oxide produced and of the unreacted chlorine present in the effluent-gas mixture. The gas is collected in an opaque 600-ml. Hempel tube it is then absorbed in a neutral 10% solution of potassium iodide. Starch indicator is added to this solution or to an aliquot, which is then titrated with 0.1 AT sodium thiosulfate solution (titration A). The amount of sodium thiosulfate used is equivalent to all the chlorine gas in the sample plus one-fifth of the chlorine(IV) oxide. The solution is then acidified with an excess of 30% acetic acid, causing a second release of iodine, which is then titrated with sodium thiosulfate solution (titration B). The amount of sodium thiosulfate used in titration B is equivalent to four-fifths of the chlorine (IV) oxide in the sample. The equations for the reactions involved are shown below.4... 

Calcium chloride solutions (pH =6.2) labeled with Ca or 36ci were displaced vertically downward through columns of homogeneous, repacked, water-saturated sandy soil by a chemically identical solution labeled with Cl or Ca, respectively. Constant water fluxes, and solution activities of 1 to 15 pCi/dm, were used. Calcium solutions were analyzed by titration with disodium dihydrogen ethylenediamine tetraacetate to a murexide end point (11). The activity of radioactively labeled solutions was obtained by liquid scintillation techniques. Concentrations of adsorbed calcium were calculated from isotope dilution. The concentration of calcium chloride in the influent solution was 0.08 N. Because exchange of calcium for itself was the only chemical process affecting transport, the calcium chloride concentration remained constant at 0.08 N throughout each experiment, both within the column and in the effluent. 

A 0.2567-g sample of a mixture of NaCl and KBr was passed through a Dowex 50 cation-exchange column, the effluent requiring 34.56 ml of 0.1023 M sodium hydroxide for its titration. What percentage of each salt was present in the mixture ... 

In generating titration curves, care should be taken that any reactions are allowed to go to completion (check for pH stabilization over about ten minutes if slow reactions are observed). The material to be titrated should be at the same temperature as the effluent to be treated, and care should be taken to avoid the loss of volatile components from samples to the atmosphere. The reagent used should be the main reagent to be used for neutralization. If problems are experienced in metering small quantities of lime-based reagents, caustic (NaOH) can be used near neutral to get sufficient resolution of the titration curve—at least one point per unit pH change should be generated. 

Ammonia TPD experiments were carried out by heating the sample in a stream of dry nitrogen up to 600 C at a heating rate of 10 C/min. The effluent gas was passed through a washing flask, and evolved ammonia purged into the flask was automatically titrated with 0.1 N HCl, sustaining a pH value of about 5. 

The effect of the ultraviolet light on the ozone concentration was determined by titrating samples collected with and without the meter in operation. At a pressure of 112 mm. of mercury, a flow of 0.3 liter per minute, and a temperature of 20°, the ozone concentration of the effluent from the meter was about 94% of that delivered to the meter. 

The reaction rate is expressed in terms of chemical compositions of the reacting species, so ultimately the variation of composition with time or space must be found. The composition is determined in terms of a property that is measured by some instrument and calibrated. Among the measures that have been used are titration, pressure, refractive index, density, chromatography, spectrometry, polarimetry, conductimetry, absorbance, and magnetic resonance. Therefore, batch or semibatch data are converted to composition as a function of time (C, t), or to composition and temperature as functions of time (C, T, ), to prepare for kinetic analysis. In a steady CSTR and PFR, the rate and compositions in the effluent are observed as a function of residence time. 

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