PETER SPENCE 263 



liquors obtained after the alum is crystallised 

 out, and which contain a considerable quantity 

 of free sulphuric acid, shall be stored in a 

 covered tank, this tank shall have a pipe at 

 the top leading to the flue or chimney, and 

 another, a lead pipe, leading into it at the 

 bottom to convey ammoniacal compounds 

 and vapour of water, obtained when ammoni- 

 acal gas liquor is being boiled or distilled, 

 into it. Sulphate of Ammonia is formed, 

 quantities of sulphuretted hydrogen are given 

 off, this gas is conveyed away to the chimney 

 and the sulphate liquor is then used in mixing 

 with the sulphate of alumina, and so forming 

 ammonia alum. It may here be mentioned 

 that the sulphuretted hydrogen is now com- 

 pletely utilised by the patent subdivision 

 combustion process of Mr. David Spence, 

 one of Mr. Spence's sons. The same 

 specification claims a process for distilling 

 ammoniacal gas liquor and other volatile, or 

 partly volatile, liquors by an arrangement 

 of two or more boilers or vessels by which 

 the liquid to be distilled can be run from one 

 to the other through the whole range, and 

 the passing of steam charged with volatile 

 matter from one to the other through the 

 whole range in an opposite direction. 



