862 



SODA, CARBONATE OF 



cent, acid, and under one-third of the total amount evolved in the process of decom- 

 posing salt by sulphuric acid iu the United Kingdom. This quantity amounts to 

 208,000 tons per annum. 



Condensation is promoted by cold and by water mainly, but next to these we must 

 add contact of surfaces and time. 



Air with a small quantity of muriatic acid in it will appear misty in moist weather, 

 though the amount may be less than Q'003 per cent. It will pass rapidly through 

 tubes well cooled and still appear misty, but lot it pass between broken pieces of coke 

 or through extremely narrow moist passages arid it will be perfectly cleared. Tha 

 floating particles too minute to fall seem, to be filtered out as we filter fine precipitates. 

 The mode of gaining extensive surface is chiefly by the use of coke in the towers. 



Other modes have been adopted of filling the condensers. Fire-bricks are used in 

 many cases, and especially at the lower part of condensers used for open roasters. 



1863 



1861 



J 11 U I] . .1- IL 



j U J 



T~7T~rf"i '\ !'!'" !'i' 

 LlL.il. .ikMI. J .- 



A condenser generally is a tower filled with moistened very porous or non-porous 

 material, in pieces so largo as to allow the passage of air and water through the inter- 

 stices, and so small as to prevent that passage from being made without contact of the 

 air or gases with the water and the solids present. 



It is built generally in the form of a square tower. It is from 3 to 6 feet square 

 equally from base to summit, and from 5 to 125 feet high. This height includes the 

 pedestal and the cistern above the condensing portion of the tower. See fig. 1862. 



1st. The simplest form of condenser allows the gas to enter below whilst the uucon- 

 densed portion escapes into the air at the top. 



2nd. The uncondensed gases of tho first tower may be sent into the top of the 



