JPS59122940A - Electrolyte for karl fischer coulometric titration - Google Patents

Abstract

PURPOSE:To increase a reaction speed, to shorten titration time, and to improve measuring accuracy, by using an electrolyte, wherein one or more specified pyridine compounds are included and I2 or iodide, SO2, alcohol, and CHCl3 are included. CONSTITUTION:A compound represented by the formula I (where R<1>, R<2>...R<5> are H, alkyl, and alkoxyl and one or more of them are alkyl or alkoxyl) and two groups of pyridine compounds are represented by th formulas II (where R<6>, R<7>...R<13> are H, alkyl, and alkoxyl, and n represents 1-5). One or more kinds of said compounds are included in an electrolyte for Karl Fischer coulometric titration in place of pyridine. The mol ratio between said compound and SO2 is made to be in the range 6:1-0.3:1. Thus the electrolyte characterized by a high reaction speed, gentle potential change in the vicinity of the terminating point of titration, and high measuring accuracy is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrolytic solution for Carl Eischer coulometric titration.

The Karl Fischer coulometric titration method is well known, and the electrolyte used is usually a solution prepared by adding a small amount of water to iodine, sulfur dioxide, pyridine, and methanol to ionize iodine. A solution containing potassium iodide or sodium iodide in place of iodine may also be used. Solutions using various aliphatic amines, heterocyclic compounds, etc. in place of pyridine have also been proposed.

Electrolytes for Karl Souscher coulometric titration have conventionally contained pyridine, which has a peculiar odor, as one of its components, which has caused inconvenience in analytical operations.

Therefore, an odorless electrolyte has been desired. Furthermore, as the electrolyte, it is desirable to use an electrolyte with a high reaction rate for the Karl Fischer reaction in order to shorten the titration time, and an electrolyte with a gentle potential change near the titration end point in terms of ease of controlling the device. has been desired for measurement accuracy.

Although it is preferable that the electrolytic solution has the above-mentioned advantages, the known electrolytic solutions mentioned above are not necessarily sufficient in this respect.

An object of the present invention is to provide an electrolyte having the above-mentioned advantages.

The present invention provides an electrolyte for Carl Souscher coulometric titration containing iodine or an iodide, sulfur dioxide, alcohol, chloroform, and at least seven pyridine compounds selected from the group consisting of (a) and (b) below. Regarding.

(B) General formula [I] 3 (wherein R1, R2, R8, R4 and R5 are hydrogen atoms, alkyl groups or alkoxyl groups, at least 7 of which are alkyl groups or alkoxyl groups) Compound (b) represented by general formula [■] (wherein, R6, R7, R♂, R9, RIOlRll,
RI2 and Rlg are a hydrogen atom, an alkyl group, or an alkoxyl group, and n is an integer of / to S. To explain the present invention in detail, the electrolytic solution consists of the following components.

Suitable iodides include iodic acid, potassium iodide, sodium iodide, and the like. The content of iodine or iodide in the electrolytic solution is 3 to 0.1% by weight in terms of iodine, preferably 0.3% by weight in terms of iodine.

Alcohols include methanol, ethanol, isopropanol, n-butanol, isobutanol, tart
- Lower aliphatic alcohols such as butanol are usually used, but ethylene glycol, propylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, etc. can also be used. The concentration of alcohol in the electrolyte is preferably 30-70%.

The concentration of sulfur dioxide greatly influences the reaction rate as well as the basicity of the base used, and even when a base with low basicity is used, the reaction will be faster if the concentration of sulfur dioxide is increased. Usually the content of sulfur dioxide in the electrolyte is 10-0. L
*-11g6, preferably 6 to 6% by weight.

Chloroform has a large dissolving power for various substances and has the effect of promoting the Karl Fischer reaction, so it is used as a component of the electrolyte. Its content is lθ to 0% by weight in the electrolyte.

The pyridine compound used as a base in the present invention is a pyridine compound represented by the above general formula [1] or (It). The alkyl group of R1, RIS is methyl, ethyl, n-propyl, n-butyl, n-
Examples include pentyl and isobutyl. Examples of the alkoxyl group include methoxyl group and ethoxyl group.

As the pyridine derivative represented by the general formula [1], R1
Compounds in which 7 to 3 out of -R5 are alkyl groups are preferred, and specific examples include picoline, lutidine, collidine, dieterpyridine, and the like.

The pyridine compound represented by the general formula [II] is a compound in which I (all of 6 to R13 are hydrogen atoms, or a compound in which 7 or more of R6 to R111 are alkyl groups, and n is a covalent group). Preferably, the compound is an integer from 1 to 1.The bonding position of the +ai1.
one in the coo position and the other in the 2- position, or both in the 2-
It may also be a position. Specifically, l: f/, 3-di(cupyridyl)propane, /, 3-di(copyridyl/I/)
Propane, etc. can be used.

As mentioned above, the molar ratio of the pyridine compound to the trapped sulfur dioxide is important for the concentration of the pyridine compound in the electrolyte.
/, preferably 3:l to 0,! ; : / is.

Although the composition of the electrolytic solution according to the present invention is the above-described energization, it may contain some other components in addition to the above-mentioned components in order to improve the performance as an electrolytic solution depending on the sample. For example, carbon tetrachloride.

Moisture determination using the electrolytic solution according to the present invention is carried out according to a conventional method. That is, an electrolytic solution according to the present invention is placed in the anode chamber, and a suitable catholyte is placed in the cathode chamber and electricity is applied to remove water in the anolyte. Water is then added to the anode housing until the iodine color disappears before use. A suitable catholyte is, for example, a mixed solution of 73% by weight of methanol, 20% by weight of carbon tetrachloride, and p% by weight of sulfur diacid.

The electrolyte according to the present invention can contain various substances, such as organic compounds,
It can be used to measure the moisture content of inorganic compounds, petroleum products, petrochemical products, etc.

Since the electrolytic solution according to the present invention does not have a bad odor and has a high reaction rate, it has the advantage that the measurement time is short and the potential change near the end point of titration is gradual.

The present invention will be explained in more detail below using Examples, but the present invention is not limited to the following Examples unless the gist of the invention is exceeded.

Example-1 and Comparative Example-/, 2 λ, 6-lutedine 2 A, g f , sulfur dioxide 3. g
11° to iodine 271. A coulometric titration device (digital trace moisture measuring device (Model !A-02,
(manufactured by Mitsubishi Kasei). A 7M methanol solution of sulfur dioxide and a l:/ mixture of carbon tetrachloride is placed in the cathode chamber. Water was injected and measured according to the operating method of the coulometric titration device described above.

The results are shown in the table. The measured values are in good agreement with those obtained when similarly measured using pyridine (Comparative Example 1), and the measurement time is shorter. Furthermore, the potential change at the titration end point is gradual, as shown in FIG. 1, and the end point can be easily detected. On the other hand, when imidazole was used and similarly measured by color, the potential change at the end of titration V (Comparative Example: l in Figure 1) was sudden and over-titration was likely to occur.

Example - Coco'IA - Collidine 30.32, Sulfur dioxide 3. gr,
Iodine, 27? , chloroform 3V is dissolved in methanol, water is added to reduce iodine, and the volume is made up to /θOm,l with methanol.

Using this electrolytic solution, measurements were carried out in the same manner as in Example-/.

Example-3 /, 3-G(l-pyridyl)pronokunta, 9f.

Sulfur dioxide6. 2, iodine 272, chloroform 3
'79'f: Dissolve in methanol, add water to reduce iodine, and then adjust the volume to 700 ag with methanol. Using this electrolytic solution, measurements were carried out in the same manner as in Example-/.

Example-G In place of /, 3-G (cupyridyl) propane and ql in Example-3, /W, ff f's /, 3-G (cupyridyl) propane gold side was used, and measurements were carried out in the same manner.

Example-5 1,3-di(2-pyridyl)propane 20.011.
Sulfur dioxide 7.70, iodine 0.64Q, ri-loform 37a are dissolved in methanol, water is added to reduce iodine, and the iodine is reduced to 100W! The capacity is 100%. Measurements were carried out in the same manner as in Example-1 using this electrolyte.

Table 1

[Brief explanation of the drawing]

The first diagram is a graph showing the potential change at the titration end point.
The solid line indicates the end point of measurement using the electrolyte solution of the present invention (Example/), and the broken line indicates the end point of measurement using the electrolyte solution using imidazole (Comparative Example λ). Applicant: Mitsubishi Chemical Industries, Ltd. Agent: Patent attorney Yo Hase - and 4 others

Claims (2)

[Claims] (1) Electrolyte for Carl Souscher coulometric titration containing iodine or iodide, sulfur dioxide, alcohol, chloroform, and at least seven pyridine compounds selected from the group consisting of (a) and (b) below. (a) General formula (wherein R1-R2, R3, R4 and R6 are hydrogen i
(2) A compound represented by the general formula (in which R6, R7, R8, R[l, RIG , R1
1, RItO and RI3 are hydrogen atoms, alkyl groups, or alkoxyl groups, and n is an integer from / to S) Compounds represented by (2) The electrolytic solution according to claim 1, wherein the molar ratio of the pyridine compound to sulfur dioxide is in the range of A:/ to o, 3:i.