Aluminium sulfacetate is a mixture of
aluminium salts dissolved in water with formula Al
2SO
4(CH
3CO
2)
4.
[1]
[2]
It is an evenly balanced mixture 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, Albert Ganswindt recommended that the use of impure sulfacetates that are empyreumatic liquids "should be abandoned" 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 each reagent controls the composition of the resulting mixture. [1] When the stoichiometric ratio of lead acetate to aluminium sulfate exceeds 3:1, the process is theoretically driven to completion and aluminium triacetate is the sole product. With less lead acetate, a mixture of aluminium triacetate and aluminium sulfacetate results that becomes increasingly rich in the latter as the reagent mole ratio approaches 2:1. This approach is used to form various mixtures for mordant applications: [1]
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]
The n = 1 and n = 2 cases, both of which are basic aluminium sulfacetates, are prepared using sodium bicarbonate along with the regents: [2]
The n = 3 case, also a basic aluminium sulfacetate, is prepared using acetic acid instead of lead acetate, along with sodium bicarbonate: [2]