Aluminium sulfacetate

Aluminium sulfacetate is a chemical compound of aluminium with formula Al
2SO
4(CH
3CO
2)
4.[1][2] It is a double salt of aluminium sulfate and aluminium acetate. It can be used as a mordant, which is a substance used to set dyes on fabrics[3] that typically contains a polyvalent metal ion like aluminium or iron,[4] In mixtures with basic aluminium diacetate or aluminium sulfacetate, aluminium triacetate has been used as a mordant with alizarin dye.[1] In 1899, Ganswindt said that the use of impure sulfacetates which are empyreumatic liquids "should be abandonded" in favour of pure preparations.[5] Empyreuma is an obsolete chemical and medical term referring to "the smell and taste associated with burning vegetable and animal matter,"[6] and likely results in this case from the use of pyroligneous acid (wood acid) or wood acid lime in the preparation of the mordant.[5]

A common approach to preparing aluminium sulfacetate is by reaction of aluminium sulfate with lead(II) acetate, the relative amount of which dictates the outcome of the reaction.[1] When the stoichiometric ratio of lead acetate to aluminium sulfate exceeds 3:1, the process is driven to completion and only aluminium triacetate is formed. Below this level, a mixture of aluminium triacetate and aluminium sulfacetate is formed, with a mole ratio near 2:1 making the latter the major product. This approach is used as mixtures have been used for mordant applications:[1]

Al
2(SO
4)
3   +   3 Pb(CH
3CO
2)
2   →   2 Al(CH
3CO
2)
3   +   3 PbSO
4

Basic aluminium sulfacetates can also be prepared, Al
2SO
4(CH
3CO
2)
4 - n(OH)
n, with hydroxide anions replacing some acetate ions. The extreme cases are aluminium sulfacetate itself (n = 0) and the double salt of aluminium sulfate and aluminium hydroxide (n = 4 case, Al
2SO
4(OH)
4). Aluminium sulfacetate is made from the hydrates of aluminium sulfate and lead acetate:[2]

Al
2(SO
4)
3•18H
2O   +   2 Pb(CH
3CO
2)
2•3H
2O   →   Al
2SO
4(CH
3CO
2)
4   +   2 PbSO
4   +   24 H
2O

The n = 1 and n = 2 cases, both of which are basic aluminium sulfacetates, are prepared using sodium bicarbonate along with the regents:[2]

2 Al
2(SO
4)
3•18H
2O   +   3 Pb(CH
3CO
2)
2•3H
2O   +   2 NaHCO
3   →   Al
2SO
4(CH
3CO
2)
3OH   +   3 PbSO
4   +   Na
2SO
4   +   2 CO
2   +   45 H
2O
Al
2(SO
4)
3•18H
2O   +   Pb(CH
3CO
2)
2•3H
2O   +   2 NaHCO
3   →   Al
2SO
4(CH
3CO
2)
2(OH)
2   +   PbSO
4   +   Na
2SO
4   +   2 CO
2   +   21 H
2O

The n = 3 case, also a basic aluminium sulfacetate, is prepared using acetic acid instead of lead acetate, along with sodium bicarbonate:[2]

Al
2(SO
4)
3•18H
2O   +   CH
3COOH   +   4 NaHCO
3   →   Al
2SO
4(CH
3CO
2)(OH)
3   +   2 Na
2SO
4   +   CO
2   +   19 H
2O

References

  1. 1 2 3 4 Georgievics, Von (2013). The Chemical Technology of Textile Fibres – Their Origin, Structure, Preparation, Washing, Bleaching, Dyeing, Printing and Dressing. Read Books. ISBN 9781447486121.
  2. 1 2 3 4 Hummel, J. J.; Knecht, Edmund (2013). Die Färberei und Bleicherei der Gespinnstfasern (in German). Springer-Verlag. pp. 116–118. ISBN 9783642912061.
  3. ↑ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (1993) "Mordant".
  4. ↑ Llewellyn, Bryan D. (May 2005). "Stain Theory – How mordants work". Archived from the original on 14 August 2007.
  5. 1 2 Ganswindt, Albert (1889). Handbuch der Färberei und der damit verwandten vorbereitenden und vollendenden Gewerbe (in German). p. 270.
  6. ↑ "Definition of empyreuma". Collins Dictionary. 2016. Retrieved 23 November 2016.
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