V. MANUFACTURES. 647 



2482. Roll Sulphur. The roll brimstone of commerce, used 

 in medicine. John Hutchinson $ Co. 



Melted sulphur run into round wooden moulds and allowed to cool. 



2483. Bicarbonate of Soda (lump), prepared by exposing 

 crystals of carbonate of soda to a current of carbonic acid gas till 

 saturated, and drying the product. John Hutchinson Sf Co. 



Soda crystals, or carbonate of soda, made by dissolving the soda-ash of 

 Leblanc's process in hot water, and, after settling, allowing to cool and 

 crystallize, are put into an air-tight iron chamber, and carbonic acid gas 

 (prepared by decomposing limestone with waste muriatic acid from the con- 

 densers) turned in by a pipe on the roof of the chamber. After some hours 

 the crystals are changed into bicarbonate of soda, part of the water of crystal- 

 lization escaping during the process. 



The moist bicarbonate is dried in kilns heated not over 100 Fahrenheit. 



2484. Bicarbonate of Soda. Carbonate of soda of the shops, 

 used in medicine and for making effervescing drinks. 



John Hutchinson $ Co. 



The dry lump bicarbonate ground in a mill and dressed to separate coarse 

 particles, as in grinding and preparing flour from wheat. 



2462. Deacon's Apparatus for exposing porous materials 

 and currents of gases to mutual action. Sectional working model, 

 illustrating the application of one form of tlie apparatus to 

 Deacon's process for producing chlorine. 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 angle of repose of the material. This increase of pressure diminishes 

 in inverse proportion to the height, and ceases when the height of the imagi- 

 nary cone is reached, all the weight of additional height above that point 

 being borne by the retaining frames. In the model, the '*' wall " and frame- 

 work- are in a cast-iron vessel, which is heated in a brick furnace. The porous 

 material is distributed to, and gathered from, the wall, by covering and in- 

 verted cones from, and to, central pipes. The gaseous current passes from 

 the outside of, and through, the " walls " to the space they and the covering 

 cone enclose, and is withdrawn from this space, or the direction of the current 

 is reversed at pleasure. 



2699. Native Peroxide of Manganese (Spanish), con- 

 taining 80 per cent, of peroxide. N. Mathieson $ Co. 



2700. Hydrochloric Acid, obtained by absorbing the gaseous 

 acid in water. JV. Mathieson $ Co. 



