OF ARTS AND SCIENCES : JANUARY 28, 1863. 101 



BaO 62.84 



AljOs 37.16 



100 

 When this precipitate was treated with water, it disso ved only par- 

 tially, leaving a considerable residue of alumina. This seems to show 

 that the neutral aluminate is not soluble without decomposition in 

 water, and to explain why in its solutions the baryta was invariably 

 found in excess. 



Beside the reactions which have been already mentioned as charac- 

 terizing the aluminates, the'solution of the precipitate by alcohol (which 

 was found to contain 64 per cent of baryta and 36 of alumina) gave 

 with nitrate of silver a voluminous, flocculent, chocolate-colored precip- 

 itate, subsiding quickly in the liquid, and soluble in ammonia with very 

 little residue. The ammoniacal solution acidified with nitric acid, 

 and then saturated with ammonia, let fall a large quantity of alumina. 



With acetate of copper it gave a precipitate of a delicate blue color, 

 in other respects resembling alumina : it was completely soluble in 

 ammonia, and from the ammoniacal solution the alumina was precipi- 

 tated by chloride of ammonium. 



A concentrated solution of chloride of calcium produced at once a 

 white flocculent precipitate, very easily and completely soluble in dilute 

 nitric acid : in a dilute solution of the same salt no precipitate was 

 formed. 



The analysis was in every case effected by first separating the baryta 

 as sulphate, then neutralizing with ammonia and completing the pre- 

 cipitation of the alumina with sulphide of ammonium. The alumina 

 was removed with a spatula from the filter after being incompletely 

 washed, redissolved in hydrochloric acid, the filter washed with this 

 acid and the alumina again precipitated and collected upon the same 

 filter. 



While endeavoring to obtain the neutral aluminate of baryta, I ob- 

 served two double salts of the aluminate with chloride of barium, and 

 others doubtless may be formed in the same way. When chloride of 

 aluminium, which for this purpose is most easily formed by precipi- 

 tating sulphate of alumina with chloride of barium, is added to a hot 

 solution of baryta, chloride of barium is of course formed, and the sep- 

 arated alumina redissolves in the excess of baryta. By further addition 

 of the chloride a permanent precipitate appears, which consists of alu- 

 mina combined with a small quantity of baryta. The filtered liquid 



11* 



