Without Reference Substance

The 2ero and the interval of the KTTS are defined without reference to properties of any specific substance. Real measurements with real gas thermometers are much more difficult than the example suggests, and all real gases condense before 0 K is reached. 

Compared to the theory of corresponding states, the reference substance method gives highly accurate results for compounds having sparse experimental data. The corresponding states method gives moderate accuracy for numerous compounds even without actual data. 

A designated primary chemical reference substance is widely acknowledged as having appropriate qualities within a specified context, and whose value is accepted without reliance on comparison to another chemical substance. 

It is largely without debate that the term "reference substance" includes those chemical and biological materials that are used as standards in a study (i.e., those materials used for response comparison purposes, such as analytical reference standards). Normally, one thinks of reference substances as just referring to specimen (sometimes referred to as "matrix samples") analyses, but the characterization of test, control, and reference substances (see... 

Since only differences between cr s for the substituents are involved, one may arbitrarily set the absolute value of one sigma value without loss of generality. Normally one chooses a hydrogen atom as a reference substituent for which o is defined as zero. All other rate constants may then be compared to the one characterizing the reaction of the reference substance (k0). In these terms equation 7.4.18 becomes... 

We are here dealing with water entirely, without reference to the atmosphere. The water of the candle had the atmosphere helping to produce it but in this way it can be produced independently of the air. Water, therefore, ought to contain that other substance which the candle takes from the air, and which, combining with the hydrogen, produces water. 

The protonated dendrimer exhibits a far more intense excimer band than corresponding Frechet dendrons without a cyclam core. One possible reason for this behaviour is that excimer formation is facilitated by folding of the - flexible - benzyl ether framework. Whereas a change in emission intensity is observed in the course of protonation of the cyclam dendrimer, a reference substance containing no cyclam and benzene moieties (Fig. 5.17) shows a linear increase... 

Fig. 5.17 Naphthyl-decorated dendrimer with cyclam core unit (according to Balzani, Vogtle et Cl/.) reference substance without dendritic branching shown in box...

It goes without saying that a non-dendritic monodansyl amino compound as reference substance will be unable to show analogous behaviour because it cannot form intramolecular niches for inclusion of cations. Thus dendritic architectures lead to specific properties which are unattainable or attainable only with difficulty in the absence of branching units. 

Evaluation of Substances Without Reference Values From the IRK/AOLG Ad-hoc Working Group... 

Measurement of the amount of substance The definition of primary methods implies that a complete uncertainty statement can be expressed in terms of the SI units without reference to a standard of the quantity being measured. Only a very limited number of methods (isotope dilution with mass spectrometry, coulome-try, gravimetry, titrimetric analysis) comply with these criteria and only these can be used for the determination of the purity of materials used in the preparation of (primary) RMs. 

A primary method [2] is one that is capable of operation at the highest metrological level, which can be completely described and for which a complete uncertainty statement can be produced in SI units. The amount of substance can be measured either directly, without reference to any other chemical standard, or indirectly, by use of a ratio method which relates the amount of unknown entity X to a chemical standard. Primary direct methods, such as gravimetry and certain electrochemical and thermal methods are the exceptions in chemistry, as the majority of measurements are made indirectly by comparison with other pure substance RMs as discussed above and below. These ratio methods include isotope dilution mass spectrometry and chromatographic and classical methods. Hence the importance of pure substance RMs. 

Note The Food Chemicals Codex, Fourth Edition, and its First Supplement, divided the infrared spectra into three categories Essential Oils, Flavor Chemicals, and Other Substances. The Committee on Food Chemicals Codex has decided to combine all three sections and place the infrared spectra in alphabetical order without reference to category. New samples of all substances whose monographs refer to infrared spectra have been run through the same infrared spectrometer to be the same size and format. 

In studies conducted in experimental animals, reliance on observation of effects alone, without reference to the duration of experimental exposure and dose/concentration, omits a fundamental concept of toxicology, i.e. all substances are potentially toxic, and what determines the toxicity is a function of the dose/concentration and the duration of exposure. In most studies conducted in experimental animals the test guidelines use an upper limit dose value. 

Etters and Kaelberer used Lennard-Jones potentials to represent rare-gas-like systems with = 3, 5, 6, 7, 8, 9, 11, and 13. Although most of their data are expressed in reduced energy and temjjerature units without reference to specific substances, for the sake of comparison with other studies, we convert the results of Etters and Kaelberer into units appropriate for Ar. In this case, = 3.4 A a = 121 K. 

Analytical Reference Standard An analytical reference standard (ARS), also known as primary standard or gold standard, is defined as a batch of drug substance, whose purity is independently established and accepted without reference to other standards. The ARS is the benchmark against... 

In the foregoing method the mean ionic activity coefficient of the solute has been calculated from actual vapor pressure data. If the osmotic coefficients for a reference substance are known over a range of concentrations, the activity coefficients of another electrolyte can be derived from isopiestic measurements, without actually determining the vapor pressures. If w, and p refer to an experimental electrolyte and wr, 0r and vr apply to a reference electrolyte which is isopiestic (isotonic) with the former, then by equation (39.46)... 

In contrast to the mole, the amount of a substance contained in one equivalent can vai7 from reaction to reaction. Consequently, the weight of one equivalent of a compound can never be computed without reference to a chemical reaction in which that compound is, directly or indirectly, a participant. Similarly, the normality of a solution can never be specified without knowledge about how the solution will be used. 

The skew k characterizes the shielding tensor without being affected by the choice of reference substance. Converting shielding into chemical shift,... 

This term denotes a substance referred to as a Class 1 Standard by suppliers (analysis certificate with, e.g., at least two assays performed by different methods) or defined by the user s own tests without reference to other substances. 

A solution of ursodeoxycholic acid (reference substance) in methanol (20 mg/ml) in a white graduated flask was allowed to stand in a window from ca. 2.0 p.m. untU ca. 10.0 a.m. the following day. From this reference substance and from a new batch to be tested, test solutions of equal concentration and also a diluted reference solution were prepared. The reference substance (100 pg and 0.5 pg) was apphed to two TLC silica gel 60 plates without fluorescence indicator, and both plates were dried for 3 min with a warm-air fan heater (grade I). One plate was then exposed to direct sunhght for 5 min. The development was then performed in the solvent system described in the DAC 1992. Figure 106 shows the two plates after derivatization with the phospho-molybdic acid reagent. 

A chemical equation representing the reaction or production of two or more gaseous substances directly indicates the volumes of the gases participating in the reaction when T and P are fixed. The volumes are related to the numbers of molecules indicated in the equation and may be evaluated without reference to the reacting weights of the gases. For example ... 

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