Concentration The amount

When micelles are formed just above the cmc, they are spherical aggregates in which surfactant molecules are clustered, tails together, to form a spherical particle. At higher concentrations the amount of excess surfactant is such that the micelles acquire a rod shape or, eventually, even a layer structure. 

There are four processes for industrial production of ahyl alcohol. One is alkaline hydrolysis of ahyl chloride (1). In this process, the amount of ahyl chloride, 20 wt % aqueous NaOH solution, water, and steam are controhed as they are added to the reactor and the hydrolysis is carried out at 150 °C, 1.4 MPa (203 psi) and pH 10—12. Under these conditions, conversion of ahyl chloride is 97—98%, and ahyl alcohol is selectively produced in 92—93% yield. The main by-products are diahyl ether and a small amount of high boiling point substance. The alkaU concentration and pH value are important factors. At high alkah concentrations, the amount of by-product, diahyl ether, increases and at low concentrations, conversion of ahyl chloride does not increase. 

Blowdown discards a portion of the concentrated circulating water due to the evaporation process in order to lower the system solids concentration. The amount of blowdown can be calculated according to the number of cycles of concentration required to limit scale formation. Cycles of concentration are the ratio of dissolved sohds in the recirculating water to dissolved solids in the makeup water. Since chlorides remain soluble on concentration, cycles of concentration are best expressed as the ratio of the chloride content of the circulating and makeup waters. Thus, the blowdown quantities required are determined from... 

Concentration The amount of a substance present in a given volume of a gas or liquid, in parts per million (ppm) or jLg m . In the case of gases, the ppm is proportional to the molecular concentration, hence the relationship between ppm and pg m " depends on the molecular weight of the gas concerned. 

The Gibbs equation allows the amount of surfactant adsorbed at the interface to be calculated from the interfacial tension values measured with different concentrations of surfactant, but at constant counterion concentration. The amount adsorbed can be converted to the area of a surfactant molecule. The co-areas at the air-water interface are in the range of 4.4-5.9 nm2/molecule [56,57]. A comparison of these values with those from molecular models indicates that all four surfactants are oriented normally to the interface with the carbon chain outstretched and closely packed. The co-areas at the oil-water interface are greater (heptane-water, 4.9-6.6 nm2/molecule benzene-water, 5.9-7.5 nm2/molecule). This relatively small increase of about 10% for the heptane-water and about 30% for the benzene-water interface means that the orientation at the oil-water interface is the same as at the air-water interface, but the a-sulfo fatty acid ester films are more expanded [56]. 

The equilibrium constant in Eq. 2 is defined in terms of activities, and the activities are interpreted in terms of the partial pressures or concentrations. Gases always appear in K as the numerical values of their partial pressures and solutes always appear as the numerical values of their molarities. Often, however, we want to discuss gas-phase equilibria in terms of molar concentrations (the amount of gas molecules in moles divided by the volume of the container, [I] = j/V), not partial pressures. To do so, we introduce the equilibrium constant Kt., which for reaction E is defined as... 

Gratzel and co-workers found in their first flash experiments that the luminescence of CdS decayed with a lifetime of 0.3 ns When methyl viologen was present, the signal of the half-reduced electron acceptor, MV, was present immediately after the laser flash. With increasing concentration, the amount of MV formed... 

There are a number of ways to introduce dopants into an EC-ALE deposit. For instance, they can be introduced homogeneously throughout the deposit, or delta doped into the structure. For a relatively homogeneous distribution, low concentrations of oxidized precursors can be incorporated into the reactant solutions. By using very low concentrations, the amounts incorporated in each atomic layer will be limited. The dopant can also be incorporated in its own cycle step. Again, a low concentration would be used so that some fraction of an atomic layer is introduced each cycle. Alternatively, a delta doping scheme can be constructed where a fraction of an atomic layer of dopant is deposited every set number of cycles. All these scenarios involve only a simple modification of the EC-ALE program. 

As shown in Fig. 6, the amount of polymerized monomer droplets strongly depends on the emulsifier concentration. With increasing emulsifier concentration, the amount of monomer initially present in the monomer droplets decreases in favor of monomer solubilized in micelles. Concurrently the fraction of polymerized monomer droplets decreases and more microgels are formed. Above a certain emulsifier concentration which is about 0.8 mol/1 in thermal initiation, the monomer is completely solubilized prior to polymerization and no polymerized monomer droplets are formed. 

Concentration The amount of a chemical agent present in a unit volume of air, usually expressed in milligrams per cubic meter (mg/m3). 

One important aspect of solutions is their concentration, the amount of solute dissolved in the solvent. In the chapter on solutions and colligative properties we will cover several concentration units, but for the purpose of stoichiometry, the only concentration unit we will use at this time is molarity. Molarity (M) is defined as the moles of solute per liter of solution ... 

Several factors influence a drug s absorption (table 3.1). Aqueous solutions are more easily absorbed than a lipid solution or solid form. Absorption of drugs in solid form is affected by the rate at which it dissolves. Higher concentrations of a drug are more rapidly absorbed than low concentrations. The amount of blood flow to the site also influences absorption heat and vasodilators increase absorption. 

Overdosed and underdosed production samples (B). Properly powdered production samples are supplied with known amounts of the API (overdosing) or a mixture of the excipients (underdosing) in order to obtain the desired range of API concentrations. The amounts of API or excipients added are usually small, so the ensuing changes in the physical properties of the samples are also small and their matrix can be assumed to be essentially identical with that of the production samples. This is an effective, less labor-intensive method than the previous one and allows the required API concentration range to be uniformly spanned. 

Isoselectivity also varies with the initiator and coinitiator concentrations. Isoselectivity decreases with increasing zirconocene and MAO concentrations in the polymerization of 1-hexene by Me2Si(H4lnd)2ZrCl2/MAO [Zhao et al., 2000], For polymerization at 50°C with [M] = 8.0 mol L mmmm) decreases from 0.90 to 0.76 when the zirconocene concentration increases from 5.2 to 104 iM with [MAO] kept constant at 62 mM. When [MAO] is increased from 4.0 to 62 mM with [zirconocene] constant at 52 pM, mmmm) decreases from 0.92 to 0.84. Polymerization at higher initiator and coinitiator concentrations at constant monomer concentration is essentially equivalent to polymerization at lower monomer concentrations at constant initiator and coinitiator concentrations. The amount of monomer available per propagating species decreases, there is more time available for epimerization, and isoselectivity decreases. 

A vendor of BioSolve technology states that the contaminant type and concentration, the amount of soil to be treated, and other site conditions will impact treatment costs (D171017, p. 1). Documents provided by the vendor indicate that the total cost of bioremediation using BioSolve can range from 25 to 90/yd of soil treated (D14680P, p. 93). Subsequent communication from the vendor stated that for remediation applications the cost of BioSolve was 1 to 5/yd of soil treated (personal communication, Jim Figueira, Western States BioSolve, October 1997). 

The maximum density of a 1-98 per cent. soln. of hydrobromic acid is 2 30°. A litre flask of an approximately normal soln. of hydrochloric acid at 15° requires the addition or subtraction of the amounts in c.c. indicated in Table X, according as the temp, is above or below the standard 15° and for one-tenth normal soln. or soln. of less concentration, the amounts indicated in Table XI. 

Male Fischer 344/N rats were exposed via the nose only for 6 h to concentrations of vinylidene fluoride ranging from 27 to 16 000 ppm [71-42 000 mg/m. Tidal volume (mean, 1.51 mL/brcath) and respiratory frequency (mean, 132 breaths/min) were not influenced by exposure concentration. Steady-state blood levels of vinylidene fluoride increased linearly with increasing exposure concentration up to 16 000 ppm. Vinylidene fluoride tissue/air partition coefficients were determined experimentally to be 0.07, 0.18, 0.8,10, and 0.29 for water, blood, liver, fat and muscle, respectively. Previously published detenninations (Filser Bolt, 1979) for the maximum velocity of metabolism in mg/li/kg) and Michaelis Menten constant (K in mg/L) are 0.07 and 0.13, respectively. Time to reach steady-state blood levels of vinylidene fluoride was less than 15 min for all concentrations. After cessation of exposure, blood levels of vinylidene fluoride decreased to 10% of steady-state levels within 1 h. Simulation of the metabolism of vinylidene fluoride mdicated that although blood levels of vinylidene fluoride increased linearly with increasing exposure concentration, the amount of vinylidene fluoride metabolized per 6-h exposure period approached a maximum at about 2000 ppm [5240 mg/m vinylidene fluoride (Medinsky et al., 1988). 

The arsenious sulphide may be formed as a crystalline precipitate under favourable conditions. When hydrogen sulphide is passed into a 0-2N solution of arsenious oxide in water, golden-yellow leaflets are formed in small quantity,7 and the amount increases with the concentration up to 0-3N. Beyond this concentration the amount of crystalline sulphide produced diminishes whilst, with very dilute solutions (0-05N), traces only are formed. The crystalline form is also obtained by heating in a sealed tube a mixture of arsenious oxide, ammonium thiocyanate and hydrochloric acid.8 If arsenic acid is used in place of the oxide, sulphur is also precipitated. A convenient... 

Sodium hydrosulphite reduces arsenates and arsenites, yielding precipitates containing sulphides the composition of which varies with conditions. In strongly acid solutions arsenic trisulphide is the main product.2 Sodium thiosulphate also precipitates arsenic as the trisulphide from acid solutions,3 but the amount of precipitation depends on the nature and concentration of the acid present. Thus, with hydrochloric, perchloric or sulphuric acid, the precipitation reaches a maximum of 50 to 80 per cent, for 0-1N acid,4 and above this concentration the amount of precipitation falls to zero with hydrochloric acid but passes through a minimum with perchloric acid at N concentration and with sulphuric acid at 2 to 3N concentration. At still higher acid concentrations precipitation becomes almost quantitative. 

Effect of addition of homopolymer, salt or conventional surfactants The effect of addition of PEO and PPO homopolymers on the gel formation of Pluronic F127 (defined in Fig. 4.3) in aqueous solution has been studied by Malm-sten and Lindman (1993). The structure, studied via SANS, and rheology of neat F127 solutions in the concentration range 10-20% has been probed by Prud homme et al. (1996). Addition of PEO can reduce the gel region and/or eliminate it at sufficiently high PEO concentration. The amount of PEO required to melt the gel depends on the copolymer concentration and decreases with... 

Invertase hydrolyzes cane sugar into glucose and fructose. The following table shows the amount of sugar inverted in the first 10 minutes of reaction for various initial substrate concentrations. The amount of invertase was set constant. 

Photocycloaddition of C-P4-C. The photochemistry of coumarin and its derivatives has been the subject of numerous investigations, mainly as a consequence of its importance in biological systems [119-127], Irradiation of 7,7 -polymethylene-di(oxycoumarin)s at low concentrations yields only syn head-to-head and head-to-tail intramolecular cyclomers. Steric factors introduced in the corresponding molecule by methyl groups at the 4-positions of the coumarins led predominantly the syn head-to-tail cyclomer (Fig. 12). At higher concentrations, the amounts of intermolecular photoproducts increase as expected. 

In an alternative approach to prepare the chiral side chain of captopril (14) and zofenopril (18), the lipase-catalyzed stereoselective esterification of racemic 3-benzoylthio-2-methylpropionic acid (19) (Fig. 8B) in an organic solvent system was demonstrated to yield i -(+)-methyl ester (20) and unreacted acid enriched in the desired S-( )-enantiomer (19) [45], Using lipase PS-30 with toluene as solvent and methanol as nucleophile, the desired S-(-)-(19) was obtained in 37% reaction yield (theoretical max. 50%) and 97% e.e. Substrate was used at 22-g/ liter concentration. The amount of water and the concentration of methanol supplied in the reaction mixture was very critical. Water was used at 0.1 % concentration in the reaction mixture. More than 1% water led to the aggregation of enzyme in the organic solvent, with a decrease in the rate of reaction which was due to... 

Enzyme concentration The amount of enzyme present in a given amount of a sample is called its concentration. As the enzyme concentration increases, the rate of the reaction also increases, because there are more enzyme molecules available to drive the reaction. Yet at a certain level, the rate stops increasing, even if more enzyme is added. Normally enzymes are present in cells in rather low concentrations. 

Concentration The amount of one substance in a system relative to the amount of other substances. 

With the help of a calibration curve obtained for known glycine concentrations the amount of glycine in the reaction mixture was calculated. 

For the non-solvent process,26 28 the pH of the starch hydrolyzate is adjusted to the optimum pH before adding the enzyme. Starch concentration is usually —15%. At higher concentrations, the yield of cyclodextrins decreases. At lower concentrations, the amount of cyclodextrins per unit weight of the starch increases, but the yield per unit volume of the reaction decreases. It is economically beneficial to utilize more starch than to recover a smaller amount of cyclodextrin per unit volume. 

The experiments with aqueous dispersions (4) indicated a somewhat different behavior, both with respect to the initial rate of flocculation and the equilibrium state. The initial rate of flocculation increased from zero to a maximum value and decreased to zero as the free polymer concentration was further increased, indicating restabilization at higher concentrations. The amount of floe phase formed has also been observed to go through a maximum with increasing free polymer concentration. The restabilization phenomenon at higher polymer concentrations could not be detected in nonaqueous dispersions (1-3). 

X may be the number of molecules, the number - concentration, the amount concentration, pressure, - entropy etc. 

The difference between clean water and undrinkable water often depends on concentration the amount of a dissolved substance in a particular quantity of a solution. For example, tap water contains a low concentration of fluoride to help keep your teeth healthy. Water with a high concentration of fluoride, however, could be harmful to your health. 

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