JPH07286985A - Analysis method for steel plate acid cleaning fluid - Google Patents

Abstract

PURPOSE:To quickly and simply titrate acid material which is hardly dissociated in water solution, with high accuracy by analyzing object solution by using titrant where material with bases is dissolved in organic solvent after foreign matters have been removed out of object solution including acid material by using a filter. CONSTITUTION:After corrosive products or non-soluble foreign matters have been removed by a filter made out of Teflon out of solution including more than one kind of acid material for example, hydrofluoric acid, nitric acid, and acetic acid (for example, steel plate acid cleaning fluid), organic solvent such as acetone is added, and sample solution is thereby be obtained. Sodium hydroxide with bases is then dissolved in water solution so as to be 5 to 14mol/liter, solution thus obtained is dispersed in organic solvent such as ethanol so as to allow titrant of 0.05 to 2.00mol/liter to be prepared, and potential titration for sample solution is thereby carried out by using the aforesaid titrant. By this constitution, nitric acid, hydrofluoric acid and acetic acid which are hardly dissociated in water solution, is separated, so that highly accurate analysis excellent in reproducibility can be performed.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for analyzing a steel sheet pickling solution.

[0002]

2. Description of the Related Art Recently, as a highly accurate and versatile titration method,
The potentiometric titration method has been widely used.

This potentiometric titration method utilizes the difference in dissociation state in the solvent to carry out titration, but it has been difficult to separate substances having no difference in dissociation state. In addition, water is usually used as a solvent for the standard solution for titration.

For neutralization titration, there is almost no problem even if an aqueous solution is used. Since this potentiometric titration method is a method of performing the titration by utilizing the difference in the dissociation state in the solvent, it was difficult to separate substances having no difference in the dissociation state in the water solvent.

Further, if a corrosion product or a substance insoluble in the solution is mixed in the solution, it may interfere with the analysis, so that the analysis may not be performed accurately and quickly.

[0006]

[Problems to be Solved by the Invention] In order to analyze a substance having no difference in dissociation state in a water solvent with good reproducibility and high precision, iron and steel, 70th year, No. 11 et al. As disclosed in, a substance that is difficult to analyze in potentiometric titration is previously subjected to diffusion dialysis using an ion exchange membrane, and then an ion selective electrode is used to selectively analyze a target substance with each ion electrode. .

However, in order to analyze many substances at once, an ion electrode having selectivity for the substances is required.

Further, it is necessary to remove in advance a substance which interferes with the ion-selective electrode by using an ion exchange membrane or the like. The present invention provides a solution analysis method for solving the above problems.

[0009]

The present invention uses a filter for removing foreign substances from a solution containing hydrofluoric acid and nitric acid, and a solution prepared by dissolving a substance having a base in an organic solvent as a solvent is used as a titration solution. It is a method characterized by using and analyzing by potentiometric titration.

As the titration solution in the present invention, 5 mol /
0.05 mol / liter or more by dispersing a basic aqueous solution of 14 liters / liter or less and 14 mol / liter or less in an organic solvent,
The method is characterized by using a solution of 2.00 mol / liter or less.

The method is characterized in that at least one of methyl alcohol (methanol), ethyl alcohol (ethanol), and acetone is used as the organic solvent for titration in the present invention.

In the method of the present invention, the sample solution is mixed with an organic solvent, and at least one of methyl alcohol (methanol), ethyl alcohol (ethanol) and acetone is used as the solvent.

Further, in the method of the present invention, sodium hydroxide or potassium hydroxide is used as the substance having a base.

[0014]

The function of the present invention will be described in detail below.

In the present invention, as a standard solution for titration, a substance having a base is dispersed in an organic solvent.

The use of an organic solvent as the solvent is a big difference from the conventional standard solution for titration.

The solvent of the titration solution is defined as an organic solvent. Solvents such as methyl alcohol (methanol), ethyl alcohol (ethanol), and acetone have a lower relative dielectric constant than water. They are 32.63, 24.3, and 20.7, respectively. Water is 25 ° C
At 78.5.

Therefore, when the same acidic substance is dissociated in the solvent, it is understood that water having a higher activity of the solvent is more easily dissociated.

On the other hand, dissociation is less likely to occur in a solvent having a low relative dielectric constant, and even substances in a dissociated state close to each other in water can be separated in a solvent having a low relative dielectric constant.
Table 1 shows an example.

Hydrofluoric acid has a pKa of 3.2 in a water solvent, and acetic acid has a pKa of 4.8, which is only about 1.6, but in an ethanol solvent, hydrofluoric acid has a pKa of 7.2, Acetic acid becomes 10.2 and spreads to about 3.0.

Similarly, it is presumed that methanol and acetone also have a lower relative permittivity than water, so that the activity of the solvent is low and dissociation hardly occurs.
By using this standard solution for titration, it has become possible to separate substances that could not be conventionally separated in an aqueous solvent.

Other than the above, butyl alcohol, amyl alcohol and the like may be used as the organic solvent.

In the present invention, the solute is defined as an aqueous solution, and when a standard solution for titration is prepared for a substance which is difficult to dissolve in an organic solvent, the standard solution for titration is not directly dissolved in the organic solvent but is dissolved as an aqueous solution. This is because they are dispersed in an organic solvent.

Further, the lower limit of the aqueous solution in which the solute is dissolved is defined as 5 mol / liter, and when it becomes 5 mol / liter or less, after that, 0.05 mol / liter or more, 2.00 This is because when the dispersion is carried out at a concentration of mol / liter or less, the effect of the concentration of the water solvent is larger than that of the organic solvent, and accurate analysis cannot be performed.

The upper limit of 14 mol / liter is specified. When the amount is 14 mol / liter or more, the amount of the solute becomes close to the saturated dissolution amount, so that it becomes difficult to dissolve the solute and a standard solution for accurate titration is prepared. This is because you cannot mix them.

As the basic substance, sodium hydroxide and potassium hydroxide are specified. Since a large amount can be dissolved in water, the concentration of the aqueous solution can be easily, quickly, and accurately.
This is because they can be mixed.

Further, since these substances are stable even in an aqueous solution, they are resistant to aging. Other than this, calcium hydroxide or tetramethylammonium may be used as the basic substance.

In the present invention, the lower limit of the concentration of a solution obtained by dispersing an aqueous solution containing a solute in an organic solvent is 0.
The amount of 05 mol / liter is specified because if the amount is 0.05 mol / liter or less, a large amount of standard solution for titration is required for titration, which is industrially uneconomical.

This is also because the standard solution concentration varies greatly. In addition, the upper limit of 2.00 mol / liter is specified. When the amount is 2.00 mol / liter or more, the concentration of water in the titration standard solution increases, so that there is no difference in the dissociation constant in the water solvent. This is because it becomes difficult to separate substances.

Further, the fact that a filter for removing foreign matters is provided is also a great difference from the conventional method.

The material of the filter is preferably Teflon, polypropylene, vinyl chloride or the like which has excellent acid resistance and corrosion resistance.

The filter size is 0.
It is desirable to use one of 0.3, 0.5 and 0.5 micron depending on the purpose.

Example 1 shows an example in which a mixed solution of hydrofluoric acid, acetic acid and nitric acid was analyzed by the method of the present invention.

As shown in Example 1, the use of the method of the present invention enables accurate analysis of acid components that could not be separated conventionally.

[0035]

[Example] As a sample solution, 50 wt% hydrofluoric acid, 70 w
Example 1 using t% nitric acid, 100 wt% acetic acid,
The mixture was prepared in the ratio shown in 2. After sufficiently stirring the sample solution, 5 cc of the sample solution was sampled using a micropipette, acetone was added to 50 cc, and potentiometric titration was performed.

A titration standard solution was prepared by dissolving sodium hydroxide in an aqueous solvent to make it 5 to 14 mol / liter, and dispersing this solution in an ethanol solvent to prepare an ethanol solvent titration solution of 0.05 to 2.00 mol / liter. Was prepared.

For comparison, the conventional method is 0.1
Potentiometric titration was also performed using a titration solution of an aqueous solution of sodium hydroxide of mol / liter.

According to the conventional method, when the separation was impossible at all or only nitric acid had the set value and the analysis value, the hydrofluoric acid and acetic acid could not be separated.

On the other hand, when the method of the present invention is used, nitric acid,
Hydrofluoric acid and acetic acid were separated, and the values agree well with the set values.

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

[Table 3]

[0043]

[Table 4]

[0044]

[Table 5]

[0045]

[Table 6]

[0046]

[Table 7]

[0047]

INDUSTRIAL APPLICABILITY The present invention makes it possible to titrate a substance in an aqueous solution, which has been difficult to analyze conventionally, by using an organic solvent as a solvent, and to provide a method which can be performed accurately, quickly and simply. It is a thing.

Claims (6)

[Claims] 1. A filter for removing foreign matter from a solution containing any one or more of hydrofluoric acid, nitric acid, acetic acid, sulfuric acid and hydrochloric acid is used, and a substance having a base is used as a solvent in an organic solvent as a titration solution. A method characterized by performing analysis by a potentiometric titration method using a dissolved solution. 2. The titration solution according to claim 1, which is 5 mol / mol.
0.05 mol / liter or more by dispersing a basic aqueous solution of 14 liters / liter or less and 14 mol / liter or less in an organic solvent,
A method comprising using a solution of 2.00 mol / liter or less. 3. A method comprising using one or more of methyl alcohol (methanol), ethyl alcohol (ethanol), and acetone as the organic solvent of the titration solution according to claim 1. 4. The method according to claim 1, 2, or 3, wherein the sample solution is mixed with an organic solvent. 5. A method comprising using one or more of methyl alcohol (methanol), ethyl alcohol (ethanol), and acetone in the organic solvent according to claim 4. 6. A method comprising using sodium hydroxide or sodium hydroxide as the substance having a base according to any one of claims 1, 2, 3, 4, and 5.