Kernforschungsanlage Julich Gesellschaft MIT Beschrankter Haftung

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Ernst Steudle

Gerd Boling

Josef Zillikens

Ulrich Zimmerman

Dieter Husken

Burkhard Stumpf

This invention relates to an apparatus for the selective determination of e concentration of a substance dissolved in a solvent by means of an osmosis cell. The osmosis cell according to the invention contains a substance not contained in the solution to be tested, which is either practically insoluble or is impermeable for the membrane. This substance reacts chemically with the substance permeating into the osmosis cell, with a product resulting from it in the cell or with a product resulting from the substance in the solution to be tested and permeating into the cell. Reaction products are thereby formed which produce a pressure in the osmosis cell, which is different from the osmotic pressure of the chemically converted portion of the substance. A pressure increase thereby occurs in the cell, from which the concentration of the substance in the solution to be tested can be determined on the basis of standard values.

Apparatus for the selective determination of the concentration of a

This invention relates to a process for the selective determination of the oncentration of a substance dissolved in a solvent by means of an osmosis cell. The osmosis cell according to the invention contains a substance not contained in the solution to be tested, which is either practically insoluble or is impermeable for the membrane. This substance reacts chemically with the substance permeating into the osmosis cell, with a product resulting from it in the cell or with a product resulting from the substance in the solution to be tested and permeating into the cell. Reaction products are thereby formed which produce a pressure in the osmosis cell, which is different from the osmotic pressure of the chemically converted portion of the substance. A pressure increase thereby occurs in the cell, from which the concentration of the substance in the solution to be tested can be determined on the basis of standard values.

Process for the selective determination of the concentration of a

In a process for the determination of the concentration of a substance dissolved in a solvent by means of an osmometer, comprising a two-chamber system with a first chamber having an osmosis cell and a second chamber for the measurement solution, to shorten the measurement time and to improve the separation of permeating components during the measurement of the concentration of the substances in the measurement solution, the pressure in the osmosis cell is held constant with an incompressible membrane arrangement, whereby with a pressure measurement apparatus in the second chamber after the replacement of a solvent, a reference solution or a calibration solution by a measurement solution, a pressure curve which corresponds to the concentrations of the nonpermeating substance and permeating substances or to the flows of the permeating substances between the osmosis cell and the second chamber is measured, and by analysis of the curve, the concentration of the nonpermeating and permeating substances in the measurement solution is determined. In one embodiment, the volume of the chamber containing the osmotic cell is varied in response to the pressure vs. time curve so as to maintain the volume flow of solvent through the membrane at substantially zero.

Process and apparatus for the determination of the concentration of a

This invention relates to a process and apparatus for the determination of he concentration of substances dissolved in a solvent. For this purpose, an osmotic cell is used, in which first, by means of an (external) reference solution, a working pressure is established, and after replacement of the reference solution by the solution to be tested, the pressure curve established in the cell is determined. The object is also to determine the concentrations of substance present in high concentration with very great absolute precision. For this purpose, an osmometer solution is selected which contains an excess of not more than 80 mOsm more than the reference solution, and in which the substances to be measured are contained in such a concentration that the difference of the concentrations of the substances in the solution to be tested and in the osmometer solution is not more than 70 mOsm. The total concentration of the substances is then determined taking into consideration the concentration of the substances in the osmometer solution. For the determination of very small deviations of the substances (less than 20 mOsm), the temperature of the solutions at the measurement point is kept constant, for which purpose there is provided an appropriate device.

Process for the determination of the concentration of substances

The invention relates to methods for the determination of the concentration of substances dissolved in a solution by means of an osmotic cell, using a pressure measurement device, and an apparatus incorporating the aforesaid osmotic cell with pressure measurement device. According to a first method, the concentrations of the substances are determined by the formation of the differences between a final pressure which is established after contact with the solution and an original and minimum pressure. According to a second method, the pressure/time course of biphasic response curves is analyzed in the vicinity of the minimum pressure, along with the rate constant for the exponential pressure increase which takes place after the minimum pressure, and the concentrations of the substances are then computed. According to a third method, simultaneous with one another, the initial slopes of the pressure/time curve of the pressure decrease in two osmotic cells are determined, and from these data, two results are determined, which are functions of the concentrations of the substances, and the concentrations of the substances are calculated from them. The reflection coefficients of both osmotic cells must thereby differ sufficiently.

Method and apparatus for the determination of substances dissolved in a

An apparatus for measuring the pressure in a very small volume, such as a ological cell or a capillary vessel. The apparatus has a space or chamber which is connected with a microcapillary tube, is pressure-tight, and is filled with a nearly incompressible medium, such as silicone oil or the like. To measure the pressure in the space, a device for converting the pressure into electrical values is connected to the space. A body, which partially displaces the medium and is moved from outside the space, extends into the space. The apparatus includes a reference electrode and another electrode which is arranged within the microcapillary tube and extends nearly to the opening of the tube. The two electrodes are electrically connected to a control device which is connected with a drive for moving the body which is provided for partial displacement of the medium. The control device is designed in such a way that by insertion or withdrawal of the body into the space, it regulates the interface (located in the microcapillary tube during the measuring process) between the medium and the fluid which penetrates the capillary tube from the volume of the cell. The regulation by the control device is a function not only of the measured value of the electrical resistance between the two electrodes as input variable, but also of a predetermined rated resistance value.

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Eckersdorf, Germany

Ernst Steudle