Extraction solutes, definition

Step Extracting Solution Operational Definition Untreated sample and Temperature... 

Method of Starch Conversion. Measure 100 ml of soluble starch solution into a 200-ml graduated flask and immerse, suitably supported, in a water-bath maintained at 21 °. Place a standardised thermometer in the flask and when the contents have reached 21 ° add, by means of a narrow-bore pipette (N.P.L. Standard), a definite volume of the malt extract solution, measured at 15°. The volume needed will depend upon the diastatic activity of the extract and will be about... 

Suspend the crude hydrochloride in some water in a separating-funnel and add 20% sodium hydroxide solution until the mixture is definitely alkaline and the crude phenylhydrazine base floats as a deep red oil on the surface. Now extract the phenylhydrazine twice with benzene (using about 30 ml. of benzene on each occasion) and dry the united benzene extracts with powdered... 

In order to maintain a definite contact area, soHd supports for the solvent membrane can be introduced (85). Those typically consist of hydrophobic polymeric films having pore sizes between 0.02 and 1 p.m. Figure 9c illustrates a hoUow fiber membrane where the feed solution flows around the fiber, the solvent—extractant phase is supported on the fiber wall, and the strip solution flows within the fiber. Supported membranes can also be used in conventional extraction where the supported phase is continuously fed and removed. This technique is known as dispersion-free solvent extraction (86,87). The level of research interest in membrane extraction is reflected by the fact that the 1990 International Solvent Extraction Conference (20) featured over 50 papers on this area, mainly as appHed to metals extraction. Pilot-scale studies of treatment of metal waste streams by Hquid membrane extraction have been reported (88). The developments in membrane technology have been reviewed (89). Despite the research interest and potential, membranes have yet to be appHed at an industrial production scale (90). 

To extract a desired component A from a homogeneous liquid solution, one can introduce another liquid phase which is insoluble with the one containing A. In theory, component A is present in low concentrations, and hence, we have a system consisting of two mutually insoluble carrier solutions between which the solute A is distributed. The solution rich in A is referred to as the extract phase, E (usually the solvent layer) the treated solution, lean in A, is called the raffinate, R. In practice, there will be some mutual solubility between the two solvents. Following the definitions provided by Henley and Staffin (1963) (see reference Section C), designating two solvents as B and S, the thermodynamic variables for the system are T, P, x g, x r, Xrr (where P is system pressure, T is temperature, and the a s denote mole fractions).. The concentration of solvent S is not considered to be a variable at any given temperature, T, and pressure, P. As such, we note the following ... 

The second step in the process is the definition of the optimal mixing time and solution temperature. It was found that for both niobium and tantalum, the mixing time for extraction and stripping must not exceed one minute. No concentration changes were observed in the temperature range of 25-50°C. 

In the extraction procedure the yellow solution is allowed to stand for 10 minutes, and then extracted with 3 mL portions of a 3 1 mixture by volume of pentan-l-ol and ethyl acetate until the last extract is colourless. Make up the combined extracts to a definite volume (10 mL or 25 mL) with the organic solvent, and determine the transmittance (460 nm) at once. Construct the calibration curve by extracting known amounts of bismuth under the same conditions as the sample. 

Only in a few cases are test samples measurable without any treatment. As a rule, test samples have to be transformed into a measurable form that optimally corresponds to the demands of the measuring technique. Therefore, sample preparation is a procedure that converts a test sample into a measuring sample. Whereas test samples represent the material in its original form, measuring samples embodies a form that is able to interact with the measuring system in an optimum way. In this sense, measuring samples can be solutions, extracts, pellets, and melt-down samples, but also definite surface layers and volumes in case of micro- and nanoprobe techniques. 

To do any extraction, you ll need two liquids, or solutions. They must be insoluble in each other. Insoluble here has a practical definition ... 

Here Zg is the number of tt electrons provided by atom is essentially an ionization potential for an electron extracted from in the presence of the part of the framework associated with atom r alone (a somewhat hypothetical quantity), is a framework resonance integral, and is the coulomb interaction between electrons in orbitals < >, and <(>,. The essential parameters, in the semi-empirical form of the theory, are cug, and and from their definition these quantities are expected to be characteristic of atom r or bond r—s, not of the particular molecule in which they occur (for a discussion see McWeeny, 1964). In the SCF calculation, solution of (95) leads to MO s from which charges and bond orders are calculated using (97) these are used in setting up a revised Hamiltonian according to (98) and (99) and this is put back into (95) which is solved again to get new MO s, the process being continued until self-consistency is achieved. It is now clear that prediction of the variation of the self-consistent E with respect to the parameters is a matter of considerable difficulty. 

In order to characterize the adsorption species on mineral surface, DDTC is oxidized into the dimmer by adding definite H2O2 into the DDTC solution, which then is extracted by cyclohexane to determine its UV spectrum. As seen from the UV spectrum in Fig. 4.33, there are three UV absorbance peaks at 230 nm, 261 nm, 280 nm respectively. The maximum absorbance peak is at 230 nm, the next peak is at 260 nm, and the weak peak is at 280 nm. The peak at 230 nm can serve as a characteristic absorbance peak, and the peak at 260nm results from absorbance overlapping of diethyl dithiocarbamate and its dimmer. 

Organic matter extracted from earth materials usually is fractionated on the basis of solubility characteristics. The fractions commonly obtained include humic acid (soluble in alkaline solution, insoluble in acidic solution), fulvic acid (soluble in aqueous media at any pH), hymatomelamic acid (alcohol-soluble part of humic acid), and humin (insoluble in alkaline solutions). This operational fractionation is based in part on the classical definition by Aiken et al. (1985). It should be noticed, however, that this fractionation of soil organic matter does not lead to a pure compound each named fraction consists of a very complicated, heterogeneous mixture of organic substances. Hayes and Malcom (2001) emphasize that biomolecules, which are not part of humic substances, also may precipitate at a pH of 1 or 2 with the humic acids. Furthermore, the more polar compounds may precipitate with fulvic acids. 

Total fluorine in fluoride supplements and dental products could be determined with minimal samples pre-treatment as for example by direct acid extraction or heating in TISAB buffer solution and subsequent determination of fluoride using fluoride ISE for the reason that entire fluorine, in these products, should be, by definition, available as free inorganic fluoride. 

For quantitative extraction of two solutes i and j, both P, and Pj should be maximised. If the ratio of the two partition coefficient is more important then the individual partition coefficients, a,j should be used as optimisation criterion (by definition indices of the partition coefficient are attached as such that is always smaller or equal to 1). Optimal values for a,j are those values which are equal to or which approximate unity ( ,v= I). 

A. It is confusing because the term is often used to refer to various preparations derived from Salvia. Technically, in pharmacy and medicine the dictionary definition of an extract is a solid preparation obtained by evaporating a solution of a drug. There is also such a thing as a fluid extract (or tincture), which is a concentrated liquid preparation containing a definite proportion of the active principles of a medicinal substance. The solvent usually used is ethyl alcohol or a mixture of ethyl alcohol and water. However various Salvia preparations are often referred to (loosely) as extracts. Q. What are the advantages of using extracts . 

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