Physical Properties
Anhydrous magnesium sulfate is a white crystalline solid occurring in alpha form as orthorhomic crystals or as a beta form having triclinic structure; density 1.507 and 1.502 g/cm3 for alphaand beta-forms, respectively; decomposes at 323°C; very soluble in water; moderately soluble in methanol (5.25g/100 mL at 15°C).
The tetrahydrate constitutes colorless monoclinic crystals; hygroscopic; density 1.454 g/cm3; melts at 80°C; highly soluble in water (120 g/100mL at 15°C); very soluble in methanol and ethanol.
Uses
Magnesium acetate tetrahydrate is used in the manufacture of rayon fiber for cigarette filters; and as a fixative for dyes in textile printing. It also is used as an antiseptic and disinfectant.
Preparation
Magnesium acetate is prepared by treating magnesium oxide with acetic acid. Magnesium oxide reacts with concentrated acetic acid in boiling ethyl acetate to produce the alpha form of anhydrous magnesium acetate. The beta form is obtained by treating the oxide with 5–6% acetic acid. In slightly hydrated isobutyl alcohol medium the product is a monohydrate, Mg(OOCCH3)2•H2O. In aqueous solution magnesium acetate crystallizes as a tetrahydrate, the commercial product. The tetrahydrate dehydrates to anhydrous salt at 134°C.
Chemical Properties
Colourless crystals or white or almost white, crystalline powder.
Uses
Used as a source of magnesium in biological reactions, and as a source of acetate ion in chemical transformations. Acts as an emission control agent in coal combustion process to reduce acid rain. It is involved in glass formation process via the thermal decomposition of solids.
Uses
Magnesium acetate [Mg(C2H3O2)2?4H2O] is used in the textile industry as a mordant
(“fixes” dyes so that they will not run). It is also used as a deodorant and antiseptic.
Uses
Used in dialysis solutions.
Purification Methods
Crystallise it from anhydrous acetic acid, then dry it under vacuum for 24hours at 100o. [Nencollas J Chem Soc 744 1956, Beilstein 2 IV 113.]
