Synthesis of Guanidine aluminum sulfate, GASH

Two solutions are prepared by dissolving 38 g of aluminum sulfate hexadecahydrate in 35 mL of boiling water and, separately, 13 g of guanidine carbonate in 13 mL of water and 4 mL of concentrated sulfuric acid. A slow addition of the acid solution is started, after which it is boiled until the evolution of carbon dioxide gas ceases. The solution is cooled down for a few minutes, after which a slow addition of sulfuric acid is started until no more CO2-gas is seen to evolve. The solution is brought to boil, then cooled down and placed in an ice bath. The crystallized mass is then subject to filtration and washed with acetone. The crude product is dissolved in 150 mL of boiling water and filtered to remove remaining insoluble matter. The solution is concentrated to approximately 50 mL in volume and placed in a dark room to stand and crystallize. The product is obtained as a hexahydrate.


Al2(SO4)3 13H2O + 2 NH2CNHNH2 ⋅ H2CO3 + H2SO4 = 2 CH18AlN3O14S2 + 2 CO2 + 3 H2O

Crystals of the pure product

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