158 CEMENTS, LIMES, AND PLASTERS. 



tate washed. The filtrate contains the molasses, which can be used 

 over again. In the course of the process a loss of 5 to 10 per cent of 

 molasses occurs. 



Closson process. This process is based on the use of magnesium 

 chloride, and is therefore of value at points such as Stassfurt, where 

 that material is obtainable as a cheap by-product. 



Twenty thousand pounds of magnesium chloride is mixed with the 

 lime-magnesia resulting from the calcination of 3000 Ibs. of magnesian 

 limestone. Water is added to give a thick solution, and mechanical 

 agitation is employed. The result is the formation of lime chloride 

 and magnesia hydrate. On passing through a filter-press the magnesia 

 hydrate is caught on the filter, while the lime chloride passes through 

 in solution. The hydrate is washed and then burned, giving one ton 

 of magnesia. The magnesia obtained at Horde by this process gave 

 the following composition: 



Silica (SiO 2 ) ] 



Alumina (A1 2 O 8 ) } 1 .05 per cent 



Iron oxide (Fe 2 O 3 ) J 



Lime (CaO) 1.94 " " 



Magnesia (MgO) 96.90 " " 



The lime-chloride solution is then treated for recovery. The mate- 

 rial is carried to receptacles like those in which blast-furnace gases 

 are washed, except that revolving wheels stir the chloride, making a 

 thorough mixture of the gases and the liquid. Two of these recepta- 

 cles are placed together back to back. A valve which can be reversed 

 sends the gases to either side and thus keeps up a continuous working. 

 Into these receptacles, together with the lime chloride, is put a quantity 

 of the lime-magnesia resulting from the calcination of magnesian lime- 

 stone. The blast-furnace gases passing through precipitate the lime 

 as carbonate, losing their carbon dioxide in the process, and are thus 

 rendered more combustible. They deposit, besides, a considerable 

 quantity of the solid materials mechanically carried by them and are 

 thus cleaned. Magnesium chloride is reformed, remains in solution, 

 and is drawn off and filtered. The entire process shows a loss of 5 to 

 6 per cent of magnesium chloride. 



Sea-water and Brines as Sources of Magnesia. 



Sea-water contains small percentages of different magnesian salts. 

 In the manufacture of table salt from sea-water or salt brines, these 

 magnesian compounds are incidentally concentrated so as to be put in 

 more available form. 



