Significance limit

Table 5.2 demonstrates how an uncorrected constant error affects our determination of k. The first three columns show the concentration of analyte, the true measured signal (no constant error) and the true value of k for five standards. As expected, the value of k is the same for each standard. In the fourth column a constant determinate error of +0.50 has been added to the measured signals. The corresponding values of k are shown in the last column. Note that a different value of k is obtained for each standard and that all values are greater than the true value. As we noted in Section 5B.2, this is a significant limitation to any single-point standardization. 

Almost any chemical reaction can serve as a titrimetric method provided that three conditions are met. The first condition is that all reactions involving the titrant and analyte must be of known stoichiometry. If this is not the case, then the moles of titrant used in reaching the end point cannot tell us how much analyte is in our sample. Second, the titration reaction must occur rapidly. If we add titrant at a rate that is faster than the reaction s rate, then the end point will exceed the equivalence point by a significant amount. Finally, a suitable method must be available for determining the end point with an acceptable level of accuracy. These are significant limitations and, for this reason, several titration strategies are commonly used. 

In Chapter 7 we examined several methods for separating an analyte from potential interferents. For example, in a liquid-liquid extraction the analyte and interferent are initially present in a single liquid phase. A second, immiscible liquid phase is introduced, and the two phases are thoroughly mixed by shaking. During this process the analyte and interferents partition themselves between the two phases to different extents, affecting their separation. Despite the power of these separation techniques, there are some significant limitations. 

Thermochemical Data. Equilibrium considerations significantly limit alcohol yield at low pressures in the vapor-phase process (116). Consequently, conditions controlling equilibrium constants have been determined and give the following relation, where Tis in K (116,117) ... 

Eijuilibrium Constant. At the pressures used in commercial production of ethanol (6.1—7.1 MPa or 60—70 atm), alcohol yield per pass is significantly limited by equiHbrium considerations. This fact has focused attention on deterrnination of equiHbrium constants and equiHbrium yields (122—124). The results of these deterrninations are as follows ... 

Multicomponent Mixtures No simple, practical estimation methods have been developed for predicting multicomponent hquid-diffusion coefficients. Several theories have been developed, but the necessity for extensive activity data, pure component and mixture volumes, mixture viscosity data, and tracer and binaiy diffusion coefficients have significantly limited the utihty of the theories (see Reid et al.). 

In some cases, the degree of fluorine contamination of tantalum and niobium oxides containing increased fluorine levels is not very critical to the later application of the oxides. Applications related to the manufacturing of optic and electronic devices, however, require significant limitations of the fluorine content of tantalum and niobium oxides. 

It should be noted here that the difficulty of accurately injecting small quantities of liquids imposes a significant limitation on quantitative gas chromatography. For this reason, it is essential in quantitative GLC to use a procedure, such as the use of an internal standard, which allows for any variation in size of the sample and the effectiveness with which it is applied to the column (see Sections 9.4(5) and 9.7). 

Mao and White developed a mathematical model for discharge of an Li / TiS2 cell [39]. Their model predicts that increasing the thickness of the separator from 25 to 100 pm decreases discharge capacity from 95 percent to about 90 percent further increasing separator thickness to 200 pm reduced discharge capacity to 75 percent. These theoretical results indicate that conventional separators (25-37 pm thick) do not significantly limit mass transfer of lithium. 

Improved methods for the preparation of reagents such as isopinocampheyl(l-isopinocam-pheyl-2-alkenyl)borinic acids will certainly lead to a more enantioselective synthesis of anti-homoallylic alcohols, since the enantiomeric purity of the reagent is the only significant limitation to the synthetic utility of this reagent system. 

Identification of unknowns using GC/MS is greatly simplified if accurate mass measurements are made of all the ions in a spectrum so that reasonable elemental compositions of each ion are available. Unfortunately, obtaining a mass measurement that is accurate enough to significantly limit the number of possible elemental compositions requires expensive instrumentation such as a double-focusing magnetic sector or fourier transform ICR MS. 

The latter report demonstrated the unique ability of this technique to resolve surface structure as well as surface composition at the electrified solid-liquid interfaces. In particular, STM has become an important tool for ex situ and in situ characterization of surfaces at the atomic level, in spite its significant limitations regarding surface composition characterization for bimetallic systems, such as the lack of contrast for different elements and the scanned surface area being too small to be representative for the entire surface. To avoid these limitations, STM has been mostly used as a complementary tool in surface characterization. 

While the shell-and-tube heat exchanger is the most common type of heat exchanger in the process industries, it does have some significant limitations ... 

One significant limitation of the RCHRES module is that it assumes total mixing in the water body thus it does not simulate stratified impoundments. 

Ga,n Significance limits of Grubb s outlier test for a risk of error a and n individual measurements ... 

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