Mr. Crum 071 the Acetates of Alumina. 311 



Precipitate from Acetate of Alumina with Chloride of Sodium. 



A solution of teracetate of alumina was produced from 1 pound acetate 

 of lead in 10 pounds water, decomposed by tersulphate of alumina. After 

 purification, common salt was added to it in the proportion of one equiva- 

 lent to one of tersulphate of alumina. The solution, when heated in 

 the water bath, became of an opaque white from the deposition of a 

 powder so very fine that the mixture passed through the filter almost 

 without change. Neither heat, nor any other application could alter 

 this character. It was left at rest, and after some weeks, the liquid 

 having become nearly clear, was poured oif, and the precipitate, which 

 had contracted into l-64th of the bulk of the liquid, was mixed again 

 with fresh water 1 1 times its volume. After several weeks more, the preci- 

 pitate fell again to the bottom of the vessel, when it was mixed with a 

 third portion of fresh water, which again, after four weeks, was decanted, 

 and the precipitate dried in a capsule at 100° Fahr. 



On analysis it yielded the following results — I do not give the details 

 of the experiments, not having made out a formula which can be stated 

 in atomic proportions : — 



Alumina, 44-66 



Acetic acid, 21-96 



Hydrochloric acid, 5-51 



Water, 25-90 



98-03 

 Chloride of sodium 1-97 



100-00 

 Nitrate of potash forms a precipitate when heated with acetate of alu- 

 mina, similar in appearance to that from common salt, but it Was not 

 particularly examined. 



Conclusions. 



1. The aluminous solution obtained by decomposing pure tersulphate 

 of alumina with the neutral acetate of lead consists, I believe, of a mix- 

 ture of binacetate of alumina, with an equivalent of free acetic acid. No 

 true teracetate of alumina appears to exist. 



2. When means arc taken to evaporate the preceding aluminous solu- 

 tion at a low temperature with sufficient rapidity, a dry substance is 

 obtained, which may be redissolvcd easily and entirely by water. This 

 is the binacetate of alumina, (Al, 0^, 2 C.. E^ O3 + 4 HO), in which the 

 alumina retains all its usual properties. 



3. When the first aluminous solution, containing not less than 4 or 5 

 per cent, of alumina, is left for some days in the cold, a salt is 

 deposited in the form of a white crust, which is an allotropic binacetate 

 of alumina, insoluble in water. Heat effects the same change in the 



