See also:

• ALKALI

The See also:

• PRODUCTION (Lat. productionem, from producere, to pro-duce)

Manufacture of See also:

• ORDINARY (med. Lat. ordinarius, Fr. ordinaire)

The process is carried out either in hand-wrought furnaces,or See also:

• MECHANICAL

3) have met with the greatest success. They consist of a See also:

• HORIZONTAL

151111 III1!III II h ~1 ~b 4!T II 1':111 VII See also:

• PALL

Nor must it be overlooked that salt-cake must be made as See also:

• LONG, GEORGE (1800-1879)
• LONG, JOHN DAVIS (1838– )

Manufacture of Hydrochloric Acid (commercially also known as " muriatic acid "). This unavoidable gaseous bye-product of the manufacture of salt-cake was, during the first part of the 19th See also:

• CENTURY (from Lat. centuria, a division of a hundred men)

On the See also:

• CONTINENT (from Lat. continere, "to hold together "; hence " connected," " continuous ")

Owing to the impossibility of employing any See also:

• METAL
• METAL (through Fr. from Lat. metallum, mine, quarry, adapted from Gr. µATaXAov, in the same sense, probably connected with ,ueraAAdv, to search after, explore, µeTa, after, aAAos, other)

The See also:

• OBJECT

The Deacon process, like the Weldon process, effects its object by the oxidizing action of atmospheric air, but in a very different manner. Weldon retained the principle of the Scheele Fig. 4.-Weldon Chlorine Still. (Sectional Elevation.) C, Stone steam See also:

• COLUMN (Lat. columna)

On a small scale it is possible to push the decomposition as far as 90 %o of the hydrochloric acid, but on the large scale only at most 6o % is reached. The mixture of hydrochloric acid and air is taken directly from the " decomposing-pan " of an ordinary salt-cake furnace, is first cooled down in pipes sufficiently to condense most of the moisture present (together with about 8% of the hydrochloric acid), and then passed through a cast-iron superheater and from this into the " decomposer." The gaseous mixture, issuing from the latter, is washed with water in the usual condensing apparatus, to remove the 40 or 50 parts of hydrochloric acid See also:

• LEFT

This produces a mixed current of pure hydrochloric acid gas and air, which is carried into a Deacon decomposer where it acts in the usual manner. The sulphuric acid, of which 6 or 7 parts are used to one of impure liquid hydrochloric acid, is always reserved for use in the same process, by See also:

• DRIVING (from " to drive," i.e. generally to propel, force along or in, a word common in various forms to the Teutonic languages)

Usually this lime is regarded only as mechanically mixed with the bleaching-compound, CaOCl2, but some chemists adopt formulae in which this lime is equally represented. For the manufacture of bleaching-powder, lime- stone of high degree of purity (especially free from See also:

• MAGNESIA

Originally the absorption of the Deacon chlorine took place in a set of chambers, constructed of large slabs of stone, containing a great many horizontal shelves superposed over one another. About sixteen such chambers were combined in such manner that the fresh gas passed into that chamber which had been the longest time at work and in which the bleaching-powder was nearly finished, and so forth until the gas, now all but entirely exhausted, reached the last-filled chamber in which it met with fresh lime and there gave up the last of the chlorine. These " Deacon chambers " occupied a large space, besides being expensive to build and difficult to keep in repair. They are now mostly replaced by an apparatus, the invention of R. Hasenclever, consisting of four horizontal cast-iron cylinders with See also:

• INTERNAL

The former kind of bleach-liquor is mostly used in the See also:

• INDUSTRY (Lat. industria, from indu-, a form of the pre, position in, and either stare, to stand, or struere, to pile up)

The Manufacture of Soda-ash from Salt-cake by the Leblanc process.—This process consists in heating a mixture ofcommercial \\ e - 2 691 – -y: ..a~~,. 4sqt ~L~1rE~I L„t t i~ s sulphate of soda (salt-cake) with about the same See also:

• WEIGHT

The inflammable gas is carbon monoxide, which, however, does not See also:

• BURN, RICHARD (1709-1785)

It consists of a number of tanks or " vats," placed at the same level and connected by pipes which reach nearly to the bottom of one tank and open out at the top into the next tank. The vats are also provided with false bottoms, outlet cocks, steam pipes and so forth. Tepid water is run in at one end of the series, where nearly exhausted black-ash is present; the weak liquor takes up more soda from the intermediate tanks and at last gets up to full strength in the last tank, charged with fresh black-ash and kept at a higher temperature, viz. 6o° C. When the first tank has been quite exhausted, the water is turned on to the next, the first tank is emptied by discharging the " alkali-waste," and is filled with fresh black-ash, whereupon it becomes the last of the series. In spite of all precautions a certain quantity of impurities is always formed, but this should be kept down as much as possible by strictly watching the temperature in the vats and by taking care that the black-ash in the wet state is never exposed to the air. The unavoidable contamination with muddy particles of vat-waste is removed by allowing the vat-liquor to See also:

• REST (O. Eng. rest, reste, bed, cognate with other Teutonic forms, e.g. Ger. Rast, Riiste, rest, and probably Gothic Rasta, league, i.e. resting or stopping place)

It is continued until the contents of the pan have been converted into a thick See also:

• PASTE (O. Fr. paste, modern pate, Late Lat. pasta, whence also in Span., Port. and Ital., from Gr. 1r&vrrl or 1raara, barley porridge, or salted pottage, ir&ao'ety, to sprinkle with salt)

This means that portion which neutralizes the acid employed for testing, and the degrees mean the percentage of Na2O thus found, whether it be present as Na2COa, NaOH, or sodium aluminate or silicate. The purest soda-ash, eqtial to too % Na2CO3, would be 581 degrees of available soda. The ordinary commercial strength of Leblanc soda-ash is from 52 to 54 degrees (in former times much was sold in the state of 48 %). 6. Manufacture of Caustic Soda.—Most of the Leblanc liquor is nowadays converted into caustic soda, as white soda-ash is more easily and cheaply made by the ammonia-soda process. We shall therefore in this place describe the manufacture of caustic soda. This is always made from the carbonate by the action of slaked lime: Na2CO3+Ca(OH)2=CaCO3+2NaOH. The calcium carbonate, being insoluble, is easily separated from the caustic liquor by filtration. But as this reaction is reversible, we must observe the conditions necessary for directing it in the right sense. These are: diluting with water so as not to exceed to % of sodium carbonate to 90 % of water; boiling this mixture; and keeping it well agitated. At the best about 92 % of the sodium carbonate can be converted into caustic soda, 8 % remaining unchanged. The operation is performed in iron cylinders, provided with an agitating arrangement.

This may consist of a steam injector by means of which air is made to bubble through the liquid, which produces both the required agitation and the heating, and at the same time oxidizes at least part of the sulphides; but this method of agitation causes a great waste of steam and at the same time a further dilution of the liquor. Many, there-fore, prefer mechanical stirring by means of paddles, fixed either to a See also:

• VERTICAL (from Lat. vertex, highest point)

Formerly the most usual concentrating apparatus was the " See also:

• BOAT (0. Eng. bdt; the true etymological connexion with Dutch and Ger. boot, Fr. bateau, Ital. battello presents great difficulties; Celtic forms are from O. Eng.)