and Manufacture of Sulphate and Muriate of Potash, 101 



portion 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 production of sulphate 

 of soda, by exposing the muriate mixed with sulphate of lime to a 

 high heat and to the current of steam. For this process I use a 

 horizontal cylinder of close fire-ware, protected on the inside from 

 the action of the lime or the sulphate by a lining of carbonate of 

 magnesia, and provided with an opening for charging capable of 

 being made air-tight. Into the top of the cylinder, at one end, a 

 steam-pipe is introduced, and from the other end, at the top, an 

 escape-pipe connects with suitable condensers for collecting the va- 

 porised salt and acid. The cylinder is half filled with a mixture 

 of equal parts by weight of sulphate of lime and muriate of soda, 

 the opening made air-tight, and the cylinder and its contents brought 

 to a red heat. A current of heated steam is then admitted, which 

 passes over the surface of the melted mixture and carries off muriatic 

 acid, with more or less volatilised salt, into the condensers. When 

 the steam escaping from the cylinder ceases to contain any notable 

 quantity of muriatic acid, the operation is discontinued and the charge 

 is withdrawn. Its soluble salts are extracted by water, and the sul- 

 phate of soda separated from any undecomposed muriate by evapo- 

 ration and crystallisation. 



In this operation the heat should not be raised so high as to cause 

 the decomposition by the steam of the sulphate of soda produced, or 

 the sulphate of lime itself. 



Though I prefer in all the above described processes heating the 

 steam highly before passing it upon the salt to be decomposed, yet 

 the same efl^ect will be produced whenever the steam and salt are in 

 contact at the proper temperature for the respective decompositions, 

 whether they have both been previously heated, or one alone heated 

 so highly as to be able to raise the other to the required tempera- 

 ture. As has been before stated, some of the salts are decomposable 

 by steam at a much lower temperature than others, but with all the 

 decomposition proceeds more rapidly in proportion as the heat is in- 

 creased. 



I claim as my invention the decomposing the sulphates of baryta, 

 strontia, lime, and magnesia, and the muriates of baryta, strontia, 

 and lime, by exposing them at a high temperature to the action of a 

 current of steam, for the purpose of obtaining the acids and the al- 

 kalies of these salts respectively. 



I also claim the decomposing the sulphates and muriates of pot- 

 ash and soda, for the purpose of obtaining the acids and the alka- 

 lies of these salts respectively, by exposing them at a high tempe- 

 rature to the action of a current of steam, alumina or the other com- 

 bining substances being present. 



