Chemistry and Physics. 265 
charge by the lower door, and replace it by fresh alumina. The with- 
drawn charge is then lixiviated with hot water, and the solution of alu- 
minate of potash or soda thus obtained is treated with carbonic acid, as 
before described. 
The lining of the cylinder should be examined occasionally, and 
kept in repair so that the fire- clay may not be corroded by the alkali. 
Provided the charge of aren in the __ is readily and equally 
permeable to the current of steam and salt vapor, the smaller the pie- 
ces of which it consists and mn greater the surface they tot 
current, the more rapidly will the decomposition of the muriate pro- 
ceed. The steam used need not be of a higher boiler pressure than 
will suffice to secure its passage through the charge in the cylinder. 
The subphosphate of alumina may be substituted for the alumina, in 
the processes for the decomposition of the sulphate and muriates of 
potash and soda, and its action is even more powerful, but its first cost 
is greater. Although to aid the decomposition of the sulphates and 
muriates of potash and soda by steam at a high temperature, the use of 
either alumina or its subphosphate is preferred as the combining sub- 
stance, yet there are a great number of substances which also possess 
the requisite properties, but act with various me ott of energy. Thus 
many salts which contain already a certain proportion of base, will yet, 
when exposed in contact with the sulphates and muriates of potash and 
soda, at a high heat, to the action of steam, form a combination with 
the potash or soda, decomposable when cold by water, or water and 
carbonic acid. The subphosphates of lime, baryta and strontia, and 
the subsilicates of lime, baryta and strontia, will under these cireum- 
stances combine with the alkali and yield it to the action of water alone 
when cold. The sulphates of baryta and strontia although themselves 
decomposable by the action of steam at high temperatures, are still ca- 
pable of thus aiding in the decomposition of the sulphates and muriates 
of potash and soda, and yield the alkali by the action of water. The 
neutral phosphates, and neutral silicates of potash and soda, when thus 
treated, form basic salts which are soluble in water and decomposable 
by carbonic acid. 
The alkalies, lime and magnesia, will also thus combine with a por- 
tion of free potash or soda which may be extracted by water. Other 
materials are capable of being used as combining substances; but I 
have named these which I consider preferable. 
The decomposition of the muriate of soda by the action of steam at 
a high temperature may be applied to the produetion of sulphate of so- 
da, by exposing the muriate mixed with suiphate of lime to a high heat 
ahd to the current of steam. For this process I use a afer c lin- 
der of close fire-ware, protected on the inside from the action 
lime or the sulphate by w lining of carbonate of magnesia, and piv ided 
with an opening for charging capable of being made air-tight. Into 
the top of the cylinder, — end, a steam pipe is introduced, and 
from the other end at the top an esca pipe race with suitable con- 
densers for collecting the eked salt and acid. al eee is half 
filled with a mixture of equal parts by weight of spat of e and 
muriate of soda, the opening made air-tight, and the ¢ 
contents brought to a red heat. A current of | 
