Bases primary standard

Should there be more than one known material, a weighted average of the individual differences (x) should be taken. The value of 5- should be based on the combined estimate from the two or more materials (perhaps different primary standards for bases). Should the materials differ markedly in composition, a plot of the individual constant errors against composition should be made. If the constant error appear to depend upon the composition, they should not be pooled in a weighted average. 

Table 11.27 Primary Standards for Aqueous Acid-Base Titrations Table 11.28 Titrimetric (Volumetric) Factors...

Selecting and Standardizing a Titrant Most common acid-base titrants are not readily available as primary standards and must be standardized before they can be used in a quantitative analysis. Standardization is accomplished by titrating a known amount of an appropriate acidic or basic primary standard. 

The majority of titrations involving basic analytes, whether conducted in aqueous or nonaqueous solvents, use HCl, HCIO4, or H2SO4 as the titrant. Solutions of these titrants are usually prepared by diluting a commercially available concentrated stock solution and are stable for extended periods of time. Since the concentrations of concentrated acids are known only approximately,the titrant s concentration is determined by standardizing against one of the primary standard weak bases listed in Table 9.7. 

Selected Primary Standards for the Standardization of Strong Acid and Strong Base Titrants... 

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

The two levels of NAAQS, primary and secondary, are Hsted in Table 3. Primary standards were set to protect pubHc health within an adequate margin of safety secondary standards, where appHcable, were chosen to protect pubHc welfare, including vegetation. According to the CAA, the scientific bases for the NAAQS are to be reviewed every 5 years so that the NAAQS levels reflect current knowledge. In practice, however, the review cycle takes considerably longer. 

Primary Standard a pollution standard based on human health effects. Primary standards are set for criteria air pollutants. See also secondary standard. 

The EPA sets two kinds of national ambient air quality standards. The primary standard is set at a level intended to protect human health with an adequate margin of safety. The secondary standard, usually less stringent, is set based on protecting the public welfare, which can include factors other than health impacts, such as reduced visibility, atid damage to crops. 

The IUPAC definition of pH39 is based upon a 0.05M solution of potassium hydrogenphthalate as the reference value pH standard (RVS). In addition, six further primary standard solutions are also defined which between them cover a range of pH values lying between 3.5 and 10.3 at room temperature, and these are further supplemented by a number of operational standard solutions which extend the pH range covered to 1.5-12.6 at room temperature. The composition of the RVS solution, of three of the primary standard solutions and of two of the operational standard solutions is detailed below, and their pH values at various temperatures are given in Table 15.4. It should be noted that the concentrations are expressed on a molal basis, i.e. moles of solute per kilogram of solution. 

When oxytocin is prescribed, the primary health care provider orders the type and amount of IV fluid, the number of units of oxytocin added to the IV solution, and the IV infusion rate An electronic infusion device is used to control the infusion rate. The primary health care provider establishes guidelines for the administration of the oxytocin solution and for increasing or decreasing the flow rate or discontinuing the administration of oxytocin based on standards established by the Association of Women s Health, Obstetric, and Neonatal Nurses (AWHONN). Usually, the flow rate is increased every 20 to 30 minutes, but this may vary according to the patient s response. The strength, frequency, and duration of contractions and the FHR are monitored closely. 

For standardizing a base solution, primary standard grade potassium biphthalate is a popular choice. Also called potassium hydrogen phthalate, potassium acid phthalate, or simply KHP, it is the salt representing partially neutralized phthalic acid and is a monoprotic weak acid. The true formula is KHC8H404. Figure 5.8 shows the chemical structure of phthalic acid and KHP. The reaction with a base is as follows ... 

What is the name of the chemical often referred to as THAM or TRIS What is its structure It does not contain OFT ions, yet it is a base. Explain. Tell why it is useful as a primary standard chemical. 

THAM, or TRIS, is tris-(hydroxymethyl)amino methane. Its structure is (HOCH2)3CNH2. It is a base because it contains the -NH2 group, which accepts a hydrogen ion to form -NH3+. It is useful as a primary standard because it possesses all the qualities sought in a primary standard, as discussed in Section 4.6.2. 

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. 

Potassium hydrogen phthalate has many uses in analytical chemistry. It is a primary standard for standardization of bases in aqueous solutions. Its equivalent weight is 204.2. It also is a primary standard for acids in anhydrous acetic acid. Other applications are as a buffer in pH determinations and as a reference standard for chemical oxygen demand (COD). The theoretical COD of a Img/L potassium hydrogen phthalate is 1.176mg O2. 

Procedures for preparing standard acid and Acids and bases in Table 11 -5 can be obtained pure enough to be primary standards.17 NaOH... 

Constant-boiling aqueous HCI can be used as a primary standard for acid-base titrations. When 20 wt% HQ (FM 36.461) is distilled, the composition of the distillate varies in a regular manner with the barometric pressure ... 

Sulfamic acid is a stable, non-hygroscopic, monoprotic acid which is very convenient to use as a primary standard in acid-base titrations. The acid hydrolyzes fairly rapidly in boiling water to give ammonium bisulfate. It may be recrystallized from water at 70°C with rapid cooling to avoid decomposition. Sulfamic acid does not dissolve appreciably in oxygenated organic solvents, e.g., alcohols, ethers. 

Calibration is based on the principle of traceability from a primary standard through intermediate standards to the test equipment, with estimates of the uncertainty which increases at each step in the chain. Wherever possible, bought in calibrations should be carried out by an accredited laboratory. It is perfectly acceptable for the test laboratory to do its own calibration but then they must maintain appropriate calibration standards and operate a measurement management system in accordance with IS01001213. One factor which has hindered full appreciation of the detailed needs of... 

ISO 1431 Part 3 was finally published in 2000. It is based on the standard calibration principle that which method is used is not important as long as its calibration can be traced to a recognised primary standard. The primary standard recognised by the atmospheric monitoring fraternity, and accepted by the standard, is a UV method. The effective result is that UV is the basic standard proposed but other types are perfectly acceptable if they are suitably adjusted to give the same answer. 

As with any analytical technique, generation of a reproducible standard curve with minimal error is critical. An assay calibration consists of several steps during which the value of the primary standard is transferred to the calibrators used in the final assay [22]. Immunoassay optimization is usually difficult due to protein heterogeneity and matrix effects and these factors, heterogeneity and matrix effects, will also affect MIP based assays [22]. 

Abstract The primary method for pH is based on the measurement of the potential difference of an electrochemical cell containing a platinum hydrogen electrode and a silver/silver chloride reference electrode, often called a Harned cell. Assumptions must be made to relate the operation of this cell to the thermodynamic definition of pH. National metrology institutes use the primary method to assign pH values to a limited number of primary standards (PS). The required comparability of pH can be ensured only if the buffers used for the calibration of pH meter-electrode assemblies are traceable to... 

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