‘ie 
x 
Chemistry and Physics. 263 
pro The subphosphate of alumina is prepared (as directed in 
cise! works) by mixing solutions of the phosphate of soda, and the 
sulphate of alumina, and adding to the solution a slight excess of am- 
monia. I mix the alumina in the state of powder with an equal weight 
of the sulphate of potash or of soda also powdered, and spread the mix- 
ture upon the hearth of a reverberatory furnace, such as I have before 
described for the decomposition of the sulphate of baryta. ‘The mix- 
ture is then heated, exposed to steam, stirred, and the o operation con- 
ducted in all respects in the manner described for the treatment of the 
sulphate of baryta. When it is desired to collect the sulphuric and sul- 
phurous acids produced by the decomposition of the sulphates of *pot- 
ash and soda, | prefer to moisten the mixture of alumina and the sul- 
phate with water, and form it into balls about half an inch in diameter, 
charge shows by the usual tests tha nes no notable proportion 
of sulphate undecomposed, the —_ iscompleted. I then withdraw — 
the charge, lixiviate it with hot water, and when the clear solution of 
aluminate of potash or soda thus ge has become cold, I pass 
then drawn off and evaporated. The alumina thus recovered is again 
used as the combining substanée. When I wish to obtain the aluminate 
of potash or of soda, I merely evaporate the solution above described 
without se oe lg the carbonic aci 
uriate of potash or of soda I merely evaporate the solution 
above iatioad without ee the carbonic aci 
“The muriate of potash or of soda may also be decomposed when ina 
fused state by the action of. steam ; alumina or the subphosphate of alu- 
mina being present, the operation is to be conducted in all respects in 
the same manner as that just described for the sulphates of potash and 
soda. But owing to the great volatility of the muriates of potash and 
soda when exposed at a high temperature to a current of air or steam, 
a large quantity of the muriate will escape with the steam and gases 
of the fire in the state of vapor undecompesed, and will be lost or will 
be difficult to condense. I prefer therefore to effect the decomposition 
of the muriates of potash and soda by causing their vapors, intimately 
mixed with highly heated age to pass slowly through a mass of small 
pieces of alumina kept a igh red heat. [use for this purpose a 
vertical fire-clay eplecler: lined with a coating of native carbonate of 
ing, which openings should be capable of being closed air-tight. 
range a cast iron retort so that its tube enters directly the cylinder near 
its bottom. The retort should have a charging door at the top capable 
of being made air-tight, through which is introduced the muriate of 
potash or soda to be decomposed. 
The muriates of potash and soda will not vaporize freely when fuse 
and highly heated, unless the atmosphere above them is Conta 
changed. This may be effected by a current of steam, and | find that 
I can sufficiently regulate the quantity of the salt volatilizec ‘from the 
