Minor species

Again consider a single spherical droplet of minority phase ( [/ = -1) of radius R innnersed m a sea of majority phase. But now let the majority phase have an order parameter at infinity that is (slightly) smaller than +1, i.e. [i( ) = < 1. The majority phase is now supersaturated with the dissolved minority species,... 

Interstellar clouds of gases contain mostly H, H2 and He, but the minority species are responsible for the interesting chemistry that takes place, just as in the earth s atmosphere. Interstellar clouds are divided into two... 

If the concentration of effective aromatic species does vary with acidity, as sometimes happens if the compound is substantially proto-nated, then the acidity-dependence of the rate will be less steep than usual, because the concentration of the active free base diminishes significantly with increasing acidity. This situation has been observed in certain cases ( 8.2). The fall in the concentration of the active species can be allowed for from a knowledge of its pK and the acidity function which, for the particular compound, gives the best measure of the acidity of the medium. Then the corrected acidity-dependence of the rate resembles that observed with compounds the concentration of which does not change significantly with acidity. The nitration of minor species is discussed later ( 8.2). 

In analyzing the behavior of these types of tetrahedral intermediates, it should be kept in mind that proton-transfer reactions are usually fast relative to other steps. This circumstance permits the possibility that a minor species in equilibrium with the major species may be the major intermediate. Detailed studies of kinetics, solvent isotope effects, and the nature of catalysis are the best tools for investigating the various possibilities. 

Subchapter F—New Animal Drugs for Minor Use and Minor Species... 

SEC. 571. CONDITIONAL APPROVAL OF NEW ANIMAL DRUGS FOR MINOR USE AND MINOR SPECIES. 

SEC. 572. INDEX OF LEGALLY MARKETED UNAPPROVED NEW ANIMAL DRUGS FOR MINOR SPECIES. 

The Minor Use and Minor Species (MUMS) amendments to the FD C Act (Sections 571, 572,573) were signed into US law in 2004. Their purpose is to make drugs legally available for use in minor species, or for the treatment of rare diseases in major species. Major animal species are defined as cattle, horses, swine, chickens, turkeys, dogs and cats. All other species are considered minor species. A drug developer can benefit from MUMS provisions in one of three ways. 

Smyth, K.C. and Crosley, D.R., Detection of minor species with laser techniques, in Applied Combustion Diagnostics, Kohse-Hoinghaus, K. and Jeffries, J.B. (Eds.), Taylor Francis, New York, 2002, Chapter 2. 

BiUter, A. et al.. Study of energy transfer processes in CH as prerequisite for quantitative minor species concentration measurements, Appl. Phys. B, 79,113,2004. 

Profile comparison of temperature, velocity, major species (CH, Oj, CO, COj, and HjO), and minor species (H, O, and OH) at the extinction state using different outer-flow conditions, for counterflow twin-stoichiometric methane/air flames. For clarity, the symbols do not represent the actual grid distribution employed in the calculation. 

Figure 5. Minor species profiles for the 9.3% (mole fraction) hydrogen-air fiame with a strain rate of a = 200 sec . ...

Analysis by SDS-PAGE shows that the membrane contains about 10 major proteins and more than 100 minor species. 

The species in an aqueous solution can be categorized broadly into two groups present at different relative concentrations. We designate those present in relatively high concentrations as major species. We refer to those present in relatively low concentrations as minor species. Minor species in aqueous solutions generally have concentrations at least three orders of magnitude lower than the concentrations of the major solute species. In most aqueous solutions, one equilibrium plays the most important role. We call this the dominant equilibrium. The dominant equilibrium always has major species as its reactants, and the products of that equilibrium often are minor species. Thus, we focus our attention on major species because they determine which equilibria are most important in the solution. 

In a solution of a weak acid, the major species are water molecules and the acid, HA. The products of the proton transfer reaction, H3 0+ and A, are present in smaller concentrations as minor species. Figure 17-5 provides a molecular view. 

Use the seven-step procedure. We want to determine pH, for which we need to know the equilibrium concentration of either H3 or OH. The major species present in aqueous ammonia are molecules of NH3 and H2 O. Both of these compounds produce hydroxide ions as minor species in solution NH3(ts q) + H2 0(/) NH4+((2 q) -b OH (a q) = 1.8 x 10" ... 

The strong base is a soluble hydroxide that ionizes completely in water, so the concentration of OH matches the 0.25 M concentration of the base. For the weak base, in contrast, the equilibrium concentration of OH is substantially smaller than the 0.25 M concentration of the base. At any instant, only 0.8% of the ammonia molecules have accepted protons from water molecules, producing a much less basic solution in which OH is a minor species. The equilibrium concentration of unproton-ated ammonia is nearly equal to the Initial concentration. Figure 17-7 summarizes these differences. 

Because 1 is several orders of magnitude larger than 2 or, we identify 1 as dominant. Notice, however, that the water equilibrium generates some hydroxide ions in the solution, so this equilibrium must be used to find the concentration of hydroxide ions. The third reaction involves a minor species, HCO3, as a reactant, so it cannot be the dominant equilibrium. However, just as the water equilibrium generates some hydroxide ions, the hydrogen carbonate equilibrium generates some carbonate anions, whose concentration must be determined. 

C17-0062. For a 1.50 M aqueous solution of hydrazoic acid, HN3, do the following (a) Identify the major and minor species, (b) Compute concentrations of all species present, (c) Find the pH. (d) Draw a molecular picture illustrating the equilibrium reaction that determines the pH. 

C17-0118. A solution is prepared by dissolving 3.5 g of P4 Oio in 1.50 L of water. The oxide reacts with water quantitatively to form phosphoric acid, (a) Identify the major species in the solution, (b) Identify the minor species in the solution and rank them in order of concentration, highest first, (c) Calculate the pH of the solution. 

The low concentration of an indicator also explains why the presence of this weak acid does not change the pH of the solution. Indicators are always present as minor species in solution, never as major species. Thus, the dominant equilibrium that determines the pH of a solution never involves the indicator. The of the substance being titrated establishes the equilibrium concentration of hydronium ions. This, in turn, establishes whether the... 

There are two possible explanations for this behavior (1) the signals come from the oxygen of minority species, such as incipient oxide nuclei, which continue to grow with exposure even though total coverage barely changes ... 

In this paper the utility of STM for studying surface reactions has been demonstrated. It is proposed that the technique makes it possible to identify the active site involved in surface reactions and that they can indeed be a minority species on the surface. 

---