SU1764689A1 - Method of solution dilution - Google Patents

Abstract

The invention relates to analytical and physical chemistry, in particular to the analysis and physicochemical studies of solutions and liquid systems, and allows speeding up the dilution process and reducing labor intensity. The method of diluting the solutions involves feeding the source solution into the vessel with siphon, sealing the vessel, filling the siphon and removing excess solution to the level of the upper end of the siphon, changing the solution volume, feeding the vessel with a known volume of solvent and mixing them. 3 ill., 7 tab.

Description

This invention relates to analytical and physical chemistry, in particular to the analysis and physicochemical studies of solutions and liquid systems.

The purpose of the invention is to accelerate the dilution process and reduce the dilution complexity.

The goal is achieved by feeding the stock solution into a vessel with a siphon and removing the excess solution to the level of the upper end of the siphon, after which the volume of the solution remaining constant in subsequent dilution cycles is measured.

The dilution of the solutions is carried out in the device shown in FIG. 1-3.

The device includes a glass dilution vessel 1, optionally with a thermostatic jacket 2, a vessel lid 3 and a solvent metering device, for example, a burette 4 with a tap 5. Into vessel 1 vp or a siphon 6 is sealed, its upper end 7 is on some distance from the bottom of the vessel. The lower end of the siphon 8 is below the lower level of the liquid in the vessel. A flexible tube 9 can be used for this. To the top of the vessel 1 is attached

a cover 3 into which one or more couplings 10 are connected to attach a metering device, a siphon and sensors to measure the properties of the solution in the vessel 1. The sensors can be inserted directly into the cover 3, for example, electrodes 12 in FIG. 2, or inserted into a vessel on the stopper (electrodes 13 in FIG. 3); In vessel 1 or in cover 3, either a plug or socket 14 is inserted to supply air or an inert gas. In the conical connection of the vessel and the lid there are two openings 15, which can be combined by turning the lid and connect the space of the vessel with the atmosphere. They serve to eliminate excess pressure when solvent is added to the vessel if an inert atmosphere is to be maintained in it. If this is not necessary, the vessel is connected to the atmosphere through nozzle 14. It is convenient to use a burette as a metering device A core 11 is attached to or attached to the vessel with a rubber tube.

The dilution is carried out as follows. When removing the lid of the vessel 1 or through the hole in the lid in the vessel serves

cl

with

H |

about

4 00 U

the initial solution, which must be diluted, in such a quantity that its level in the vessel is slightly higher than the upper end of the siphon 7. Overpressure is applied through the pipe 14 and the siphon b is filled with a solution. The excess solution is removed to the level of the upper end of the siphon 7. Measure the remaining volume of the solution in the vessel (by weighing the vessel with and without solution, measuring the height of the liquid column, etc.). This dilution volume is always constant and is determined only by the distance of the upper siphon 7 from the bottom of the vessel 1. This distance is controlled by interchangeable siphons of various lengths (Fig. 1). After establishing the level of liquid in vessel 1 at the height of the upper end of the siphon 7 from burette 4 using a crane 5, the solvent is added to the vessel in an amount necessary for the desired dilution of the solution. In this case, the vessel must be connected to the atmosphere by aligning the holes 15 or through the nozzle 14. After adding the solvent or during the dilution process, the solution in the vessel 1 is mixed. After the solution has reached homogeneity, the vessel is disconnected from the atmosphere and, by creating pressure through pipe 14, an excess amount of solution is squeezed out through siphon 6 as described above. After this operation, the volume of solution V0 remains in the vessel, and the volume of solution equal to the volume V of solvent added from the burette flows out of the vessel. Further, the dilution of the solution is carried out in a similar manner until the desired concentration is reached. The degree of dilution is controlled by the amount of solvent added to vessel 1. The concentration of the diluted solution after a single addition of solvent is determined by the formula

gg vq

 ° V0 + V

where Co and C are the concentration of the solution before the addition of the solvent and after the addition;

Vo and V are the volume of solution before dilution and the volume of solvent added, respectively,

If the initial solution is diluted many times in equal doses of the solvent, the concentration of the diluted solution through n dilutions will be

V p Cn Co (v ° y).

To measure the properties of the solutions or use them for other purposes, use the part of the solution that collects after displacing from vessel 1. A constant volume of solution remains in the vessel after decreasing concentration after each dilution, which is convenient when measuring the properties of a series of solutions in the vessel,

Examples of the specific implementation of the proposed solution dilution method are given below.

Example 1. Preparation of calibration solutions of potassium sulfate in the determination of sulfates in drinking water (GOST 4389-72. Drinking water. Methods for determining the content of sulfates.).

In a vessel 1 (Fig. 1) with a volume of about 200 ml, 4 ml of a basic standard solution of feSCM (500 mg 5 cm2 per 1 l) are injected from a pipette. Then 26 ml of distilled water are added. The mixture is stirred with a magnetic stirrer and the excess solution is displaced, creating an overpressure rubber

pear. The volume of solution remaining in the vessel is equal to 92.8 ml (determined by weighing the water and dividing the mass by the density of the water at the temperature of weighing). So get the top concentration to build

calibration curve (20 mg / l). Then dilute the solution with distilled water from a burette. The resulting concentrations of sodium sulfate are shown in table 1.

After each displacement of the solution, the first portion is discarded (to rinse the siphon), and 5 ml is taken from the remaining solution for photometry. In tab. 1 shows two dilution options. AT

Variant I maintains concentration intervals approximately equal to those required by GOST 4389-72, and in Variant I, in the concentration range of 8–10 mg / l, the concentration range is narrowed to increase the calibration accuracy. The time of preparation of a series of solutions (in one of the options) is 20 minutes by the proposed method and 40 minutes by the dilution method in volumetric flasks according to GOST 4389-72.

PRI mme R 2. Preparation of calibration solutions for the determination of P20e in phosphorus-containing fertilizers.

20 ml of a standard solution of 200 mg / l of potassium phosphate monobasic and 80 ml of distilled water are introduced into the vessel of Example 1. The mixture is stirred and excess solution is squeezed out of the vessel. 92.8 ml of a 40 mg / L solution remains in the vessel. Next, the solution is diluted with distilled water. Concentrations are given in table. 2

The preparation time of the solutions is 15 minutes, according to the manual 30 minutes.

Example 3. Platinum electrodes for measuring electrical conductivity are hollowed into the vessel lid (Fig. 2). In the vessel pour 15 ml of an aqueous solution of potassium chloride with a concentration of 0.01 mol / L. After displacing the excess solution through a siphon, 12.47 ml of solution remains in the vessel (determined by weighing). Next, dilute the solution with equal doses of distilled water in 5 ml. The conductivity measurements are carried out after each addition of water, mixing and displacing the excess solution at a constant level of solution in the vessel. In parallel, measurements of solutions prepared by sequential double dilution in volumetric flasks are carried out. The results of the dilution are presented in table. 3

The preparation time of the solutions and the measurement of conductivity when diluted in a vessel is 45 minutes (14 points), while diluting in flasks — Zch 20 minutes (7 points) with significantly greater labor intensity due to the need to wash the vessel after each measurement.

Example 4. Measurement of the electrical conductivity of a mixture of hydrogen peroxide - isopropyl alcohol to determine the composition of the complex formed by these substances.

15 ml of isopropyl alcohol is introduced into the vessel of Example 3. After displacing the excess alcohol through the siphon, 5 ml of a 30% aqueous solution of hydrogen peroxide (concentration 9.77 mol / l) are introduced into the vessel. The mixture is stirred, the excess is squeezed out and the conductivity is measured. Next, dilute with 5 ml of hydrogen peroxide solution. The resulting concentrations are given in table. four.

Example 5: Preparation of aqueous solutions of sodium dodecyl sulfate to measure surface tension.

Into the vessel according to Example 3, 15 ml of a 5 g / l sodium dodecyl sulfate solution are introduced. After displacing excess solution through a siphon, dilution with distilled water in equal doses of 15 ml is carried out. The resulting concentrations are given in table. five.

The preparation time of the solutions was 15 minutes. It takes 40 minutes to prepare 10 solutions in volumetric flasks with much more labor.

Example 6. Construction of a calibration curve for determining the concentration of bromide ions.

A bromine-selective electrode and a silver-chloride reference electrode are inserted into the cap of the vessel in the form of a plug (Fig. 3). 10 ml of a 0.1 N solution of methyl bromide are introduced into the vessel.

potassium and excess are squeezed out. 8.58 ml of solution remain in the vessel. Dilution is made in equal doses of 15 ml of 1 mol / l solution of magnesium sulphate. After each dilution

measure the value of the EMF of the electrode system. The resulting concentrations are given in table. 6

The preparation time of the solutions and measurement of the activity of the bromide ions is 20 minutes,

guide (see example 2) - 40 min. The calibration accuracy of this method is higher due to the greater number of points.

Example 7. Deep Dilution

biological drug.

7 ml of the rabbit antibody-to-mouse immunoglobulin G conjugate conjugate with an initial dilution of 1: 3000 are introduced into the vessel (Fig. 1). After displacing the excess solution

4.8 ml of solution remain in the vessel. Dilution is carried out with distilled water in doses of 20 ml. The concentration of the resulting solutions are given in table. 7

The time taken to dilute the stock solution for 29 orders of time was about 1 hour. When using pipettes for 40 dilutions, at least 2 hours are required with high labor intensity.

The proposed solution dilution method is particularly effective for constructing calibration dependencies in mass analyzes at work, as well as for finding values at infinite dilution in scientific studies.

Claims (1)

Invention Formula A method of diluting solutions, comprising feeding the vessel into the initial solution and measuring its volume, feeding the vessel into a vessel of known volume and mixing, characterized in that, in order to speed up the dilution process and reduce labor intensity, the initial solution is fed into the vessel with a siphon, then the vessel seal, fill the siphon and remove the excess solution to the level of the upper end siphon followed by measuring the volume of the solution. Table 1 Table 2 Table3 Table4 Table Table Table Fig. / Continuation of table 7 FIG. 2