Ammonium carbonate group

The ammonium carbonate group ((NH ₄ ) ₂ CO ₃ group) is part of the cation separation process , a classic method of qualitative analysis in inorganic chemistry.

This cation group precipitates there from the filtrate of the ammonium sulfide group preceding in the separation step , if this is mixed with the separating agent concentrated ammonium carbonate solution. The ammonium carbonate group includes those elements which form sparingly soluble carbonates with the release agent ( precipitation reaction ); Example:

${\displaystyle \mathrm {CO_{3}^{2\operatorname {-} }+BaCl_{2}\longrightarrow BaCO_{3}\!\downarrow +2\,Cl^{\operatorname {-} }} }$

Barium carbonate precipitates out together with strontium carbonate and calcium carbonate . Thus, the following alkaline earth metal elements belong to the ammonium carbonate group in the form of their cations: Ca ²⁺ , Ba ²⁺ and Sr ²⁺ - the filtrate then only contains the cations of the soluble group .

Separation of the ammonium carbonate group

The precipitation of the alkaline earth metal cations is followed by their separation so that they can then be found - undisturbed by cations such as magnesium - with the help of detection reactions or by means of flame coloring . The carbonates precipitated in this way can be dissolved in acids for separation:

${\displaystyle \mathrm {2\,CO_{3}^{2\operatorname {-} }+4\,HCl\longrightarrow 2\,CO_{2}\!\uparrow +4\,Cl^{\operatorname {-} }+2\,H_{2}O} }$

Excess precipitant ((NH ₄ ) ₂ CO ₃ ) breaks down when boiling into the gases from which it is industrially manufactured:

${\displaystyle \mathrm {(NH_{4})_{2}CO_{3}\longrightarrow 2NH_{3}\uparrow +CO_{2}\uparrow +H_{2}O} }$

The alkaline earth cations are then separated from one another and detected individually. Since they are very similar in their chemical properties, this separation is quite difficult.

literature

• Michael Wächter: chemistry laboratory . Verlag Wiley-VCH, Weinheim 2011, pp. 240ff, ISBN 978-3-527-32996-0
• Gerhart Jander: Introduction to the inorganic-chemical internship. 13th edition, S. Hirzel Verlag, Stuttgart 1990, ISBN 3-7776-0477-1 .
• Michael Wächter: Substances, particles, reactions. Verlag Handwerk und Technik, Hamburg 2000, ISBN 3-582-01235-2 , p. 169.
• Bertram Schmidkonz: Practical course in inorganic analysis. Verlag Harri Deutsch, Frankfurt 2002, ISBN 3-8171-1671-3 .

Web links

Wikibooks: Practical course in inorganic chemistry / ammonium carbonate group  - learning and teaching materials