TO SODA AND POTASSA. 359 
by ammonia, and identical in the relations of alumina to sulphuric acid with native 
aluminite. The compound formed in the resolution differs from the compound ob- 
tained by Unverdorben,* and in crystallized form by Fremy,+ by saturating boiling po- 
tassa with alumina, in that it contains half an atom of potassa more. "This is not more 
striking than the contrast displayed between the compound in the resolution of alumina 
in soda, and the body produced by Schaffgotsch by melting carbonate of soda and alu- 
mina together. 
The sulphuric acid required to re-precipitate the alumina somewhat exceeded one 
equivalent. | 
l4 atoms KO = 2 of 0.0736 gram. = 0.0552 gram. KO. 
0.0552 gram. KO correspond with 0.0469 * SO, 
1.5 c. c. of sulphuric acid solution contain 0.04896 * — SO,. 
The formula most nearly expressing the reaction would be, 
2 A1,0,.3 KO + 380, = 2 AlO; + 8 [KO . $0,]. 
It appears, therefore, that while all the alumina is thrown down by sulphuric acid 
from its soda solution with an equivalent. of soda in combination not saturated, it is not 
entirely precipitated from its potassa solution by the same reagent till all the potassa 
has been withdrawn by the sulphuric acid, or till an equivalent of sulphuric acid for all 
the potassa has been added. 
The chloride of ammonium required to re-precipitate the alumina from its solution in 
potassa is somewhat more than two equivalents of the chloride to one of the potassa 
in combination with the alumina. 
14 atoms of KO — 0.0552 gram., which corresponds with 0.0626 gram. NH,CI. 
4.3 c.c. of chloride of ammonium solution contain 0.1421 < NH,CL 
It is doubtless true with this, as with the corresponding soda result, that the quantity 
of chloride of ammonium required to produce precipitation, is influenced by the degree 
of dilution of the reagents. 
The above result is most nearly expressed by the formula, 
- The compound most nearly allied to this is Rose’s compound of chloride of alumi- 
num and ammonia, 
Al, C, 3 NH;, 
obtained by passing dry ammoniacal gas over chloride of aluminum. 1 
* Pogg. Ann., VII. p. 323. T Compt. Rend., XV. p. 1106. 
i Pogg. Ann, XXIV. p. 228. 
