Carbonate error

The effective concentration of the base is thus diminished by absorption of carbon dioxide, and a systematic error (called a carbonate error) results. 

A carbonate-free NaOH solution was found to be 0.05118 M immediately after preparation. Exactly 1.000 L of this solution was exposed to air for some time and absorbed 0.1962 g CO2. Calculate the relative carbonate error that would arise in the determination of acetic acid with the contaminated solution if phenolphthalein were used as an indicator. 

The solid reagents used to prepare standard solutions of base are always contaminated by significant amounts of carbonate ion. The presence of this contaminant does not cause a carbonate error provided that the same indicator is used for both standardization and analysis. It does, however, lead to less shaip end points. 

A NaOH solution was 0.1019 M immediately after standardization. Exactly 500.0 mL of the reagent was left exposed to air for several days and absorbed 0.652 g of CO2. Calculate the relative carbonate error in the determination of acetic acid with this solution if the titrations were performed with phenolphthalein. 

Coulometric titrations of acids are much less susceptible to the carbonate error encountered in volumetric methods (see Section 16A-3). The error can be avoided if carbon dioxide is removed from the solvent by boiling it or by bubbling an inert gas, such as nitrogen, through the solution for a brief period. 

Capillary electrophoresis High-speed, high-resolution electrophoresis performed in capillary tubes or in microchips. Carbonate error A systematic error caused by absorption of carbon dioxide by standard solutions of base that will be used in the titration of weak acids. 

This situation, despite the fact that reliability is increasing, is very undesirable. A considerable effort will be needed to revise the shape of the potential functions such that transferability is greatly enhanced and the number of atom types can be reduced. After all, there is only one type of carbon it has mass 12 and charge 6 and that is all that matters. What is obviously most needed is to incorporate essential many-body interactions in a proper way. In all present non-polarisable force fields many-body interactions are incorporated in an average way into pair-additive terms. In general, errors in one term are compensated by parameter adjustments in other terms, and the resulting force field is only valid for a limited range of environments. 

The chief danger and main source of error in a combustion is that of moving the Bunsen forward a little too rapidly and so causing much of the substance to burn very rapidly, so that a flash-back occurs. This usually causes an explosion wave to travel back along the tube towards the purification train, some carbon dioxide and water vapour being carried with it. If these reach the packing of the purification train they will, of course, be absorbed there and the results of the estimation will necessarily be low. 

The source of carbon dioxide. The main requirement of the carbon dioxide supply is that it shall be air-free. It is, however, almost impossible to generate carbon dioxide, by any fairly simple method, so that it is completely free from air. Nevertheless, it is possible to obtain the gas sufficiently pure so that no serious error is introduced into the determination. 

The simplest analytical procedure is to oxidize a sample in air below the fusion point of the ash. The loss on ignition is reported as graphitic carbon. Refinements are deterrninations of the presence of amorphous carbon by gravity separation with ethylene bromide, or preferably by x-ray diffraction, and carbonates by loss of weight on treating with nitric acid. Corrections for amorphous carbon and carbonates are appHed to the ignition data, but loss of volatile materials and oxidation may introduce errors. 

Be is the critical pressure, MPa. Values of Ap from Table 2-383 are summed for each part of the molecule to yield X Ap. Calculation of the Platt number is discussed under Critical Temperature. Errors in average 0.07 MPa and are less reliable for compounds with 12 or more carbon atoms. 

The average error for hydrocarbons of twelve or less carbon atoms is about 0.01 mVkmole. 

The resultant viscosity is in centipoise (mPa-sec) if 7 and 7 are given in K and Pa, respectively. This method can also be used for hght nonhydrocarbon gases except for hydrogen where, special N s are required. For hydrocarbons below ten carbon atoms, average errors of about 3 percent can be expected, with errors increasing to 5-10 percent for heavier hydrocarbons. 

The procedure of simultaneous extracting-spectrophotometric determination of nitrophenols in wastewater is proposed on the example of the analysis of mixtures of mono-, di-, and trinitrophenols. The procedure consists of extraction concentrating in an acid medium, and sequential back-extractions under various pH. Such procedures give possibility for isolation o-, m-, p-nitrophenols, a-, P-, y-dinitrophenols and trinitrophenol in separate groups. Simultaneous determination is carried out by summary light-absorption of nitrophenol-ions. The error of determination concentrations on maximum contaminant level in natural waters doesn t exceed 10%. The peculiarities of application of the sequential extractions under fixed pH were studied on the example of mixture of simplest phenols (phenol, o-, m-, />-cresols). The procedure of their determination is based on the extraction to carbon tetrachloride, subsequent back-extraction and spectrophotometric measurement of interaction products with diazo-p-nitroaniline. 

Protection potentials are usually determined experimentally because of the possibilities of error. Figure 2-9 shows experimental results for the potential dependence of weight loss rates for carbon steel [29,30]. Four curves are plotted at 25°C for the following media ... 

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