Constant proportions

A simple treatment is stiU possible if it may be assumed that the flux of the component of interest A through the interface stays in a constant proportion to the total molar transfer through the interface over the entire tower ... 

When the feedstock contains constant proportions of reactive impurities, the rate of decline also may depend on the concentration of the main reactant, thus ... 

In the opposite case, PA < 1, the Raman process with the rate constant proportional to is... 

In this way, ihe emissive power of a grey body is a constant proportion of the power-emitted by the black body, resulting in the curve shown in Figure 9.35 where, for example, e = 0.6. The assumption that the surface behaves as a grey body is valid for most engineering calculations if the value of emissivity is taken as that for the dominant temperature of the radiation. 

The cycles of carbon and the other main plant nutrients are coupled in a fundamental way by the involvement of these elements in photosynthetic assimilation and plant growth. Redfield (1934) and several others have shown that there are approximately constant proportions of C, N, S, and P in marine plankton and land plants ("Redfield ratios") see Chapter 10. This implies that the exchange flux of one of these elements between the biota reservoir and the atmosphere - or ocean - must be strongly influenced by the flux of the others. 

Paleodiet studies have focused on the analysis of collagen, due to its ability to survive in ancient bone. Like all proteins, collagen is composed of amino acid (AA) units present in relatively constant proportions characteristic of the specific protein. The isotopic composition of a sample of collagen is the weighted average of the 5 C values of each of the constituent amino acids. 

The operation principle of these TFTs is identical to that of the metal-oxide-semiconductor field-effect transistor (MOSFET) [617,618]. When a positive voltage Vg Is applied to the gate, electrons are accumulated in the a-Si H. At small voltages these electrons will be localized in the deep states of the a-Si H. The conduction and valence bands at the SiN.v-a-Si H interface bend down, and the Fermi level shifts upward. Above a certain threshold voltage Vth a constant proportion of the electrons will be mobile, and the conductivity is increased linearly with Vg - Vih. As a result the transistor switches on. and a current flows from source to drain. The source-drain current /so can be expressed as [619]... 

Eutectic point (Tc) A single point on a temperature concentration phase (or state) diagram for a binary solution (e.g., water and sugars or salts) where the solution can exist in equilibrium with both crystalline solute and crystalline solvent. Under equilibrium conditions, cooling at Te results in simultaneous crystallization of solvent and solute in constant proportion and at constant temperature until maximum solidification has occurred (based on Fennema, 1996). 

When [X ] and [Nu ] are constant in the aqueous phase by keeping the aqueous phase saturated with M+X and M+Nu , the Q+Nu and Q+X in organic phase will be in constant proportion. 

Quantitative methods using flame emission photometry cannot be absolute because an unknown, although relatively constant, proportion of the sample will reach the flame of which only a further small proportion of atoms will actually be excited and subsequently emit radiation. Hence it is essential to construct calibration curves for any analysis. The radiation emitted by the flame when pure solvent is sprayed is used to zero the instrument and the maximum reading set when the standard with the highest concentration is sprayed. 

This is an exponential process and a constant proportion of drug is eliminated in a given time. 

This time a constant amount of drug is eliminated in a given time rather than a constant proportion. First-order elimination may become zero order when the elimination system (often a metabolic pathway) is saturated. 

The Law of Constant Proportion" -- The same chemical compound always contains the same elements, and there is a constant ratio between the weights of the constituent elements present. 

Berthollet (1748-1822) denied the tmth of the law of constant proportion, and a controversy ensued between this chemist and Proust (1755-1826), who undertook a research to settle the question, the results of which were in entire agreement with the law, and were regarded as completely substantiating it. 

An intermediate of the type Co(NH3)4NH + is postulated in (4.45). The subsequent reactions of this intermediate should be independent of the nature of the X group in the starting material. The results of early experiments to verify this point have represented some of the most powerful support for the mechanism. Base hydrolysis of Co(NH3)jX + in an H2 0/H2 0 mixture was found, as required, to give a constant proportion of Co(NH3)5 OH + and Co(NH3)5> OH +, independent of X being Cl, Br or NO3-. The competition experiments described in Sec. 2.2.1 (b) support a five-coordinate intermediate which is so short lived that it retains the original ion-atmosphere of Co(NH3)jX "1+ but has lost memory of the X group. ... 

Avogadro s number, N° (=6.02 10 ) gives the number of molecules in that many gramms of a chemical compound as the value of its molecular weight. If, for the sake of simplicity, we assume that the chemical formula of the molecule is X Ym than its molecular weight is nAx+mAy and there are N°n atoms of the X element and N°m atoms of the Y element in the nAx+mAy gramms of that compound. The important feature of the molecule here is the constant proportion of its constituents (and not the type of bond between them). 

Because water is a universal solvent, at least some of virtually every element is present as a solute in seawater. As shown in Table 3.1, the most abundant substances in seawater are the major ions (Cl , Na", SO4 , Mg ", Ca ", and K" ). They are present in nearly constant proportions in the open ocean because their concentrations are largely controlled by physical processes associated with water movement, such as transport by currents, mixing via turbulence, evaporation, and rainfall. These solutes are also referred to as conservative ions. Most of the rest of the solutes in seawater are not present in constant proportions because their concentrations are altered by chemical reactions that occur faster than the physical processes responsible for water movement. These chemicals are said to be nonconservative. Though most substances in seawater are nonconservative, they collectively comprise only a small fraction of the total mass of solutes and solids in the ocean. 

Because the major ions are present in nearly constant proportions, the salinity of seawater can be inferred from any of their individual concentrations. The easiest concentration to measure is that of the chloride ion, which is also the most abundant. In practice, this concentration is determined by titrating a sample of seawater with a standardized solution of silver nitrate. The reactions that take place are ... 

This constancy in relative ion concentration was first postulated by Alexander Marcet in 1819 and, hence, is known as Marcet s Principle or the Rule of Constant Proportions. Formally stated, it says that regardless of how the salinity may vary from place to place, the ratios between the amounts of the major ions in the waters of the open ocean are nearly constant. ... 

As noted earlier and shown in Table 3.9, small deviations in the proportions of the major ions have been observed particularly in coastal and pore waters. Reasons for these exceptions to the rule of constant proportions are described briefly next and addressed at length in later chapters. 

Small amounts of salt are commonly occluded in sea ice. Not all of the ions are incorporated to the same degree. This alters the ion ratios in the remaining brine, leading to deviations from the Rule of Constant Proportions during freezing. Likewise, meltwater from sea ice can contain ions in ratios that deviate from average open ocean water. 

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