Mr. Ceum on the Acetates of Alumina. 301 



Acetic acid, 50'63 



Alumina, 25-86 



Water, 23-51 



100-00 

 The formula, AljjOs, 2A + 5H0, requires — 



Acetic acid, 51-41 



Alumina, 25-91 



Water, 22-68 



100-00 



II. Insoluble Binacetate of Alumina, 2 Hydrate. If heat be applied 

 to the strong solution of acetate of alumina, described in the previous 

 page, it speedily becomes turbid, and deposits a heavy white powder, 

 which falls readily to the bottom of the vessel. In a couple of days, 

 at 100° Fahr., a considerable quantity of this powder is deposited ; 

 but in two or three hours at 160°, and in much shorter time at boiling 

 heat, the whole of the salt is thrown down, and nothing remains in the 

 liquid but acetic acid, excepting a trace of alumina, just distinguishable 

 by carbonate of soda. 



The precipitate has a crystalline shining appearance in the moist state, 

 and seems, under the microscope, to consist of small oval particles of uniform 

 size. It falls into fine powder in drying, after which, when mixed with 

 water, it remains for a long time in suspension. Boiling water does not 

 free it from chloride of sodium, of which it contains about O'l per cent. 



To remove that impurity, the substance is to be dissolved with the 

 assistance of heat in two equivalents of rectified sulphuric acid, diluted 

 with three times its weight of water. The solution is decomposed by 

 fiubacetate of lead — 



AlA, 2A + 2SO3 + 2PbO, A 

 =AL03. 3A + 2(PbO, SO3) 



and the filtrate freed from lead and sulphuric acid as before. When heat 

 is now applied to this solution, a precipitate is obtained, in which no 

 trace of alkali or of chlorine can be detected. 



A portion of the substance obtained at a boiling beat, and dried 24 hours 

 at 100° Fahr., yielded 29-83 per cent, of alumina. Another portion dried 

 48 hours gave 30-54 per cent. Burned with oxide of copper, 1-697 grains 

 of the salt, dried at 100" Fahr., indicated 59-87 per cent, of acetic acid. 

 In another experiment 1-005 grains indicated 58-88 per cent. The 

 mean is 59-37. The substance is, therefore, composed of — 



Acetic acid, 5937 



Alumina, 30-18 



Water 10-45 



100-00 



