Standardization acid and base

Reference Procedure Preparing Standard Acid and Base... 

How to prepare standard acid and base solutions, pp. 43, 44 Common laboratory apparatus for handling and treating samples, p. 44 How to filter and prepare precipitates for gravimetric analysis, p. 48 How to sample solids, hquids, and gases, p. 52 9 How to prepare a solution of the analyte, p. 53... 

Data and Calculations The difference between the initial and final buret readings is the volume of standard acid and base used in the titration of the Grignard reagent. 

Inorganic Analysis Acid-base titrimetry is a standard method for the quantitative analysis of many inorganic acids and bases. Standard solutions of NaOH can be used in the analysis of inorganic acids such as H3PO4 or H3ASO4, whereas standard solutions of HCl can be used for the analysis of inorganic bases such as Na2C03. 

Thompson, R. Q. Identification of Weak Acids and Bases by Titration with Primary Standards, /. Chem. Educ. 1988, 65, 179-180. 

Arsenic trioxide may be made by burning arsenic in air or by the hydrolysis of an arsenic trihaUde. Commercially, it is obtained by roasting arsenopyrite [1303-18-0] FeAsS. It dissolves in water to a slight extent (1.7 g/100 g water at 25°C) to form a weaMy acidic solution which probably contains the species H AsO, orthoarsenous acid [36465-76-6]. The oxide is amphoteric and hence soluble in acids and bases. It is frequendy used as a primary analytical standard in oxidimetry because it is readily attainable in a high state of purity and is quantitatively oxidized by many reagents commonly used in volumetric analysis, eg, dichromate, nitric acid, hypochlorite, and inon(III). 

Most chemicals used in the procedure will appear in the index. Thus, there will generally be entries for all starting materials, reagents, intermediates, important by-products, and final products. Most products shown in the Tables in the discus.sion sections of this volume are included unless the compounds are quite similar in which case a general descriptive name was entered. Chemicals generally nut indexed included coiimion solvents, standard inorganic acids and bases, reactants shown in the Tables, and compounds cited in the discussion section in connection with other methods of preparation. 

Log k appears to correlate with log P for standards between log P —0.5 to 5.0. One limitation of this method is that solutes must be electrically neutral at the pH of the buffer solution because electrophoretic mobility of the charged solute leads to migration times outside the range of Tm and TEof- Basic samples are therefore run at pH 10, and acidic samples at pH 3, thus ensuring that most weak acids and bases will be in their neutral form. This method has been used in a preclinical discovery environment with a throughput of 100 samples per week [24]. 

Unless standards are prepared in buffered media, positive or negative deviations may result from measurements made at 348 nm or 372 nm respectively Alternatively, measurements can be made at the isosbesticpoint, i.e. where the absorbance curves of each form intersect, and where absorbance is not a function of equilibrium concentrations but only of the overall concentration. Solutions of weak acids and bases should also be measured at their isosbestic points for the same reason. 

One very important use of E and C numbers is the calculation of heats of interaction for systems which have not been examined experimentally. From our knowledge of the standard deviations of the parameters and their correlation coefficients, we have calculated the expected standard deviations for calculated heats for all possible combinations of all but a few of the acids and bases listed in Tables 3 and 4. For the hydrogen bonding acids and sulfur dioxide, these predicted standard deviations nearly all lie between 0.1 and 0.3 kcal/mole. For other systems with much larger heats, the errors are somewhat worse than this averaging around 0.7 kcal mole-i. 

Part of this chain is formed by the analyst in his/her laboratory (the "end user"), while part of it may be formed between NIST and the vendors. For example, a laboratory analyst can purchase a primary standard acid (which a vendor can certify as traceable to an SRM) for solution standardization and then base a number of secondary standardizations, such as acids and bases, on that one primary standard. Similarly, an analyst can purchase an atomic absorption reference standard (which a vendor can again certify as being traceable to an SRM) and then make one or more dilutions of this reference standard before creating the final series for the standard curve. 

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