Carbonates of alumina, glucina, iron, chromium, etc. 325 



Muspratt does not mention whether he tested the substance for 

 ammonia, which it should contain, according to H. Eose,* who 

 finds that the precipitate, after being washed, first with hot and 

 then with cold water, has the composition, Al^O,, 3H0+NH,0, 

 SCOj +H0. Langloisf finds the precipitate bj alkaline carbon- 

 ates iQ the salts of alumina to be 3(A1,03, C0,)+5(Al,O3, 8H0). 

 Wallace:}: precipitates the chlorid by carbonate of soda, in very 

 dilute solution, and dries the precipitate over sulphuric acid. He 

 gives the formula, SAl.O^, 200^, 9H0. Bley§ obtains percent- 

 ages of carbonic acid varying from 5-27 to 11-39, in the precipi- 

 tate, produced by alkaline carbonates in solutions of alum, and 

 considers it to be a mere mixture, of variable composition. Bar- 

 ratt|j finds that the precipitate by carbonate of soda in chlorid of 

 aluminum, after washing, drying, rubbing with water and again 

 washing and drying over sulphuric acid, consists of alumina, free 

 from carbonic acid. 



The precipitates, which I have examined, were precipitated by 

 carbonate of soda, in slight excess, from alumina-potash-alum, 

 free from iron. The mode of analysis, used in the iron and 

 chromium compounds, was not applicable in this case. The 

 strongly alkaline wash-water, from the ignited alumina, contained 

 alumina in large quantity, showing that aluminate of soda had 

 been formed and carbonic acid, therefore, driven out of the car- 

 bonate of soda. Attempts to overcome this difficulty, by taking 

 ^'eighed quantities of alum and carbonate of soda, in equivalent 

 proportions, and by exactly neutralizing the solution of alum by 

 carbonate of soda, did not give good results. The method finally 

 adopted was to wash the substance with water saturated with 

 carbonic acid, until a portion of the filtrate, after being boiled to 

 «xpel carbonic acid, gave no alkaline reaction. This would 

 probably give correct results, since the water, bemg already sat- 

 urated with carbonic acid, would hardly wash out any from the 

 substance. The latter, moreover, would hardly absorb any more 

 carbonic acid from the water, since, during the precipitation, free 

 carbonic acid is given off in great quantity and the alumina must 

 nave combined with as much carbonic acid as it would be possi- 

 ble for it to take up. In other respects, the smalyses were con- 

 '^"-'-J '•■ ' ^ - ' ' -- -^ - — The following are 



20-87 2068 2405 18-63 \%Q9 -^"^^ -_ 



Tmm 100^ loooo loo-oo loooo loooo loo- 



Inn., xcii. 452. t Ann.Chim. et Phys, [3] dvi 



}a2., 1858. 410, in Jahresb.. 1858. 70. § J- pr- Chera., xxxix, 1 



!fews, i, 110, ia J. pr. Chem., Ixxxii, 61. 



