the manganese liquor is mixed with limestone dust. The donkey 

 pump forces the neutralised liquor into the three chloride of 

 manganese settlers on the top, which are fitted with swivel 

 pipes for running off the liquid to any depth without dis- 

 turbing the sediment. From these tanks the liquor passes to 

 one of the two circular towers which are the oxidisers, and in 

 these the liquor is mixed with milk of lime, and air and steam 

 are blown through it. From the oxidisers the pasty mixture is 

 conveyed to the mud- settlers, which are just above the level 

 of the stills, so that the settled mud is conveniently transferred 

 to the stills. The horizontal twin engine is used for blowing, 

 &c., and near it is the tank in which the milk of lime is made. 



170. Specimens illustrating manufacture of bleaching 

 powder, employing Weldon's method of chlorine genera- 

 tion. 



1876. Exhibited by N. Mathieson tf Go. 



No. 1. Native peroxide of manganese (Spanish), containing 

 80 per cent, of peroxide. 



No. 2. Hydrochloric acid, obtained by absorbing the gaseous 

 acid in water. 



No. 3. Chloride of manganese from native " manganese " 

 stills after neutralisation with carbonate of lime. 



No. 4. Limestone dust. Crushed carbonate of lime. 



No. 5. Manganese mud, as precipitated before blowing with 

 air. 



No. 6. Manganese mud, after oxidation by blowing. 



No. 7. Burnt lime, from Buxton, Derbyshire. This lime is 

 unslaked. 



No. 8. Hydrate of lime, sifted and ready for the bleaching 

 powder chambers. 



No. 9. Bleaching powder, containing 38 per cent, of chlorine. 



171. Deacon's apparatus for exposing porous materials 

 and currents of gases to mutual action. Sectional working 

 model, illustrating the application of one form of the 

 apparatus to Deacon's process for producing chlorine. 



1876. Exhibited by Henry Deacon. 



In this example, the layer or " wall " is vertical and circular, 

 and forms a section of a cylinder. The frames resemble those 

 of Venetian blinds, with the laths inclined at an angle of 45, 

 and so far apart, that an imaginary line joining the upper edge 

 of each lath and the lower edge of the one above it is more 

 horizontal than the natural angle of repose of the porous material 

 itself, which is thus retained and supported by each lath in 

 succession. A "wall "of this kind on being raised in height 

 adds to the pressure on the bottom, layers only so long as the 

 height is less than that of a cone whose base is the width of the 

 " wall," and whose sides are at the same angle as the natural 



