JPS60219555A - Solvent for measuring moisture by karl fischer technique - Google Patents

Abstract

PURPOSE:To shorten a measuring time to a large extent, in the measurement of moisture by Karl Fischer technique, by adding triethylamine to methanol being a reaction solvent. CONSTITUTION:According to the operation of JIS Karl Fishcer technique, methanol is added at first so as to completely immerse an electrode but, at this time, triethylamine is added to methanol in an ranging from above 1/16vol to 3vol to one vol of methanol. Subsequently, a Karl Fischer reagent is added to bring the interior of a flask to an anhydrous state. Hereupon, a predetermined amount of pure water is added by using a microcylinder and the Karl Fischer reagent is added at a speed of about 2-3 drops/sec and a time, when a reaction speed became slower than a definite value, is set as a final point. By this method, the required time of 7-12min in the JIS method is reduced to 2min or less and a measuring time is shortened to a large extent.

Description

DETAILED DESCRIPTION OF THE INVENTION Karl Fischer reagent is the best method for measuring moisture because it reacts only with water in hydrated materials, but the reaction between this reagent and water is due to the presence of iodine, which is a component of the reagent. It is said to be a Tamana concerted reaction between sulfur dioxide gas, pyridine, methanol as a solvent component, and water in the sample to be measured, so the order of the reaction is at least fifth order, and the reaction rate becomes very slow near the end point. Therefore, there is a drawback that measurement time is long. To avoid this, stop dropping when a certain amount of excess reagent is added than the water content (the amount of reagent used up to this point is All11), and over time the excess reagent will react with the remaining water. When it disappears, drop the excess reagent again (the amount of reagent used up to this point is B ml)
. Generally, the end point is when the waiting time until (B-Δ) mJ of reagent is consumed exceeds a certain time (1 to 0°5 minutes), that is, when the reaction rate becomes slower than a certain value. It is used. Therefore, by increasing the rate constant of the fifth-order reaction, the measurement time can be shortened.

Therefore, the present inventor discovered that by adding triethylamine to methanol, which is one of the reaction solvents, the measurement time can be shortened by a large amount. Furthermore, triethylamine does not have an adverse effect on moisture measurement as seen in the examples. The present invention is 5.
This relates to the solvent of the sample placed in the titration flask in the ill'l determination of JrS water content (Karl Fischer method). According to JIS, the solvent used is about 25 ml of Karl Fischer methanol. First, dissolve the sample in this solvent 1. Add an appropriate amount of Kar Fischer reagent to make it anhydrous. Next, add Karl Fischer reagent dropwise and wait. When the time is 30 seconds, the time from the beginning of dropping to the end point is 7 to 2 minutes in the case of Example 1 where the amount of water added is 3/j l, but when using JIS methanol instead When using the solvent of the present invention, the same operation takes less than 2 minutes, which shortens the fixed time by as much as 11 times, making it a breeze! It is convenient for

Example 1. 118 Following the Karl Fischer method, first add methanol until the electrode is fully submerged, and at this time add 1/1/2 of triethylamine to the amount of methanol.

Add content. Next, Karl Fischer reagent is added to make the inside of the titration flask anhydrous. Next, add 3 μl or l Ou of pure water using a microsyringe, and add JIS Karl Fischer reagent every 2 to 10 seconds.
J I
A comparison with the measurement results obtained when S methanol (Karl Fischer River) was used instead of the above-mentioned liquid mixture revealed the following results. The experimental data listed below is the result of successive additions of reagents to the same reaction solvent.

Therefore, in the first stage example, the average time required to add 3 μl of water is 1 minute and 28 seconds, and from this the waiting time of 30
The average of reagent usage r11 is 0.88ml in 58 seconds after subtracting the seconds.
(about! 30 drops) is to be /J[・.

This is 1.5 drops per second, so it is almost continuous dripping.
This shows that the d111 constant was turned off at t.

Example 2 Same as Example J, but with water addition la of 3
The ratio of methanol to 1 heliethylamine was determined as shown in the table only for the case where 711 was used.

Total 1 The ratio of methanol to 1-ethylamine is 16
:1 or more, the required time for 41 exceeds 2 minutes, so the effect of 76 addition of 1-ethylamine is small.

Note 2: Methanol vs. triethylamine content! ＋'
Since the wipes separate in the container, titration is not performed.

Special fl applicant name: Hikosuke Watanabe

Claims (1)

[Claims] 1 volume of methanol and '/1 volume of triethylamine. Solvent for moisture measurement by Karl Fischer method with a volume of more than 3 volumes or less