Amine number

The amine number is the amount of KOH in mg, which equates to the amine content of 1 g of substance.

General

	DIN 53176
Area	Binders for coating materials
title	Determination of the amine number of water-thinnable binders
Latest edition	2002-11
ISO

Amines are organic-chemical compounds that are derived from ammonia : One or more hydrogen atoms in ammonia are e.g. B. replaced by an alkyl radical .

According to DIN 53176, the amine number is determined by potentiometric titration . This means that the pH value is determined.

Aqueous amine number

Amines react like ammonia in aqueous solution.

${\displaystyle \mathrm {NH_{3}+H_{2}O\longrightarrow NH_{4}^{+}+OH^{-}} }$ ammonia

${\displaystyle \mathrm {R{-}NH_{2}+H_{2}O\longrightarrow R{-}NH_{3}^{+}+OH^{-}} }$ Amine

The hydroxyl group is determined by titration with an acid, for example HCl .

${\displaystyle \mathrm {R{-}OH+HCl\longrightarrow R{-}Cl+H_{2}O} }$

The consumption of the acid is equated with the consumption of KOH for the calculation.

A blind and a main experiment are titrated.

The weight of the substance depends on the expected amine number:

Amine number	Initial weight
until 10	10-15
10-30	5-10
30-50	2-5
50-150	1-2
150-300	0.5-1

The amine number is calculated as follows:

The consumption of the blank test is subtracted from the consumption of the main test and multiplied by the molar mass of KOH (56.1 g / mol) and the concentration of KOH. Then you divide by the weighed in amount of the substance to be analyzed .

Non-aqueous amine number

With the non-aqueous amine number, the reaction medium is acetic acid (anhydrous).

Primary, secondary and tertiary amines

There are titration methods that allow all three amine numbers to be determined side by side.

literature

• Standard DIN 53176: 2002-11 Binders for coating materials - Determination of the amine number of water-thinnable binders ( beuth.de )