Concentration Levels Of Solution Research Articles

Study of the coprecipitation of calcium, potassium, sodium and chloride with barium sulfate using atomic spectrometry and visible spectrophotometry

Sulfate ions at the 50 and 250 mg l–1 SO42– levels are precipitated gravimetrically as BaSO4 from 200 ml samples using a large excess of BaCl2. Atomic absorption or emission spectrometry and visible spectrophotometry are applied to ten pairs of BaSO4 precipitates obtained from each of two concentration levels of standard Na2SO4 solution with or without 4 g of the cation being studied, to determine the Na, K, Ca and Cl ions present as impurities, after dissolution of the BaSO4 precipitates with hot, concentrated H2SO4. The experimental results, Δexp, are compared with the theoretical values, Δcalc, calculated from a model that assumes that all the anion precipitates as BaCl2 and all the cation as the sulfate of the respective cation. Good agreement with the model is found for the cations studied.

Soil solute concentration and water uptake by single lupin and radish plant roots

Soil water extraction (Q) and the corresponding values of matric (Ψ m ) and osmotic (Ψ π ) potentials near single roots of eighteen day old lupin and radish plants, subjected to two levels of transpirational demand and five Na + soil solution concentration levels, were determined using a combination of computer assisted tomography applied to gamma and X-ray attenuation measurements and Na + -LIX microelectrodes (...)

Soil solute concentration and water uptake by single lupin and radish plant roots

Application of computer assisted tomography to gamma and X-ray attenuation measurements and Na+-LIX microelectrodes were used to determine the spatial distributions of soil water content and Na+ concentrations respectively near single roots of eighteen day old lupin and radish plants. These quantities were monitored at root depths of 3, 6 and 9 cm and at zero, 2, 4, 6, and 8 hour intervals from the diurnal commencement of transpiration. The plants were subjected to two levels of transpirational demand and five Na+ soil solution concentration levels. Water extraction rates for the lupin and radish roots increased continuously with time but were substantially reduced with increasing Na+ concentration in the treatment. Water uptake was uniform along the length of the essentially constant diameter lupin roots but decreased along the tapering radish roots as the diameter and hence the surface area per unit length of the roots decreased. The accumulation of Na+ at the root surfaces of both plants increased gradually with time in a near linear fashion and was slightly higher under the higher transpiration demand. These increases were not exponential as would be expected with non-absorption by the roots and this is considered to be due to back diffusion at the relatively high water contents used. At these water contents matric potentials had a much smaller influence on transpiration than osmotic potentials. The relationships between leaf water potentials (Ψ1) and osmotic potentials at the root surfaces were linear with the decreases in Ψ1 almost exactly reflecting the decreases in Ψπ indicating rapid plant adjustment. Leaf water potentials decreased progressively with time and the relationships between leaf water potential and the transpiration rate were also linear supporting the suggestion of constant plant resistances at any given concentration.

Limit of detection in barium sulphate gravimetry for water analysis

Sulphate ions in the 1–5 mg l–1 SO42– range can be determined gravimetrically in 200-ml samples using a large excess of barium chloride. From ten determinations at each of three concentration levels of standard sodium sulphate solution, the analytical calibration function calculated by weighted least squares is xc(mg l–1 SO42– found)=(0.093 ± 0.064)+(1.008 ± 0.039)c(mg l–1 SO42– added) with 95% confidence intervals. The limit of detection is cL= 1 mg l–1 SO42–(k= 3). A systematic approach is suggested for determining the limit of detection, by considering the variance of both the blank and the calibration function.

Computer simulated dissolution of carbide precipitates in alloys

AbstractConventional theory on the dissolution of a spherical particle of a second phase in an alloy is shown to be inappropriate when considering carbide species. In particular, the assumptions of an error function solute concentration profile and a constant equilibrium solute concentration level at the interface cannot be made. A model for computer simulated dissolution is therefore proposed which is based on the diffusion of solute away from a carbide particle across discrete shell increments. The method is used to predict times for complete and partial dissolutions of M23C6 particles in Nimonic 80A (registered trade mark of Henry Wiggin and Co. Ltd). As a result, the effect of solution heat treatment of the alloy is more clearly understood and practical improvements are recommended.

Radiotracer studies on calcium ion-selective electrode membranes based on poly(vinyl chloride) matrices

Radiotracer studies with (45)Ca and (36)Cl demonstrate that PVC matrix membranes containing Orion 92-20-02 liquid calcium ion-exchanger are permselective to counter-cations. Diffusion coefficients are quoted for the migration of (45)Ca between pairs of calcium solutions and are discussed in terms of solution concentration, membrane thickness and concentration level of sensor in the membrane. Migration of calcium ions from calcium chloride solution to a Group (II) metal chloride solution through a PVC membrane containing calcium liquid ion-exchanger is discussed in terms of solvent extraction and electrode selectivity coefficient parameters. Thus, magnesium, strontium and barium ions appear to inhibit migration through the membrane by their low affinity for the membrane liquid ion-exchanger sites, while the inhibition by beryllium ions is attributed to site blockage by the strong affinity of dialkylphosphate sites for beryllium.

Cadmium Absorption and Growth of Various Plant Species as Influenced by Solution Cadmium Concentration

AbstractSolution culture techniques were used to study the response of corn, turnips, beets, beans, tomatoes, cabbage, lettuce, green peppers, and barley to Cd levels in solution in the range of 0.1 to 10 µg/ml. Tolerance of the plants to Cd varied. Growth of beets, beans, and turnips was reduced by 50% at Cd solution concentrations of 0.2 µg/ml. Similar growth reductions for corn and lettuce occurred where the solution concentration level was about 1 µg Cd/ml. Tomatoes and barley were somewhat more tolerant with levels of about 5 µg Cd/ml required to produce 50% growth reduction. Cabbage, the most tolerant plant species tested, showed 50% growth reduction at Cd solution concentrations of 9 µg/ml.Cadmium concentrations of plant leaves increased as the amount of Cd added to the substrate solution increased. Amounts accumulated when the solution concentration was 0.1 µg/ml varied between 9 µg/g (bean leaves) and 90 µg/g (corn leaves). At solution concentrations of 1.0 µg Cd/ml the range was 35 µg/g (bean leaves) to 469 µg/g (turnip leaves). Similarly at 10 µg Cd/ml the range was 175 µg/g (barley) to 112 µg/g (tomato leaves). The results presented show that plants vary in their tolerance to Cd solution levels and their leaves are capable of accumulating excessive Cd amounts when the solution concentration is of the order of a few tenths of a µg/ml.