288

CHLORATE OF POTASH.

The figures upon the preceding page represent, one of the two chimneys recently erect-ed at the Camden Town station, for the steam boilers of the two engines of 60 horse-povrer each, belonging to the London and Birmingham Railway Company. These engines draw their train of carriages up the inclined plane of Hampstead Hill. The chim-neys were designed by Robert Stephenson, Esq., engineer to the Company, executed byWilliam Cubitt , Esq., of Gray’s Inn Road,—and do equal honor to both gentlemen,being probably the most elegant and substantial specimens of this style of architecture inthe world. In the section, fig. 281,

A represents a bed of concrete, 6 feet thick, and 24 feet square.

s, brick footings set in cement j the lower course 19 feet square.

c, Bramley-fall stone base, with a chain of wrought iron let into it.

D, a portion, 15 feet high, curved to a radius of 113 feet, built entirely of Malmpaviors, (a peculiarly good kind of bricks.)

E, shaft built of Malm paviors in mortar.

F, ditto, built from the inside, without exterior scaffolding.

G, the cap ornamented (as shown in the plan alongside) with Portland stone, thedressings being tied together with copper cramps and an iron bond.

Fig. 282 ^presents the mouldings of the top, upon an enlarged scale.

Fig. £83, a plan of the foundation, ditto.

'Fig. 284, ditto, at the level of the entrance of the flue, as seen in

Fig. 285, the elevation of the chimney.

Fig. 286, plan at the ground level i, in figs. 281 and 285.

K , fig. 281, the lightning conducting rod.

CHINTS is a peculiar style of fast-printed calico, in which figures of at least five dif-ferent colors are impressed upon a white or light colored ground.

CHLORATE OF POTASH, commonly called oxymuriate of potash. This interestingsaline compound has become thq object of a pretty extensive manufacture, in consequenceof its application to make matches for procuring instantaneous light, and a detonatingpowder for fire-arms. It may be prepared both in the humid and dry way.

Having made a strong solution of purified potash, or carbonate of potash, with fromtwo to three parts of water, we pass through it in a Woulfe’s apparatus a current of chlo-rine gas, till it ceases to absorb any more. Chloride of potash and chloride of potassiumalone are formed as long as there is an excess of alkali in the solution ; but afterwards,in the further reaction of the materials, the chloride passes into the state of a chlorate,and, as such, precipitates from the solution. During the first half of the operation, thatis, till the potash be about one half saturated with chlorine, as indicated by litmus paperceasing to be darkened and beginning to be blanched, only the chloride of potassium ormuriate of potash falls. The process should be interrupted at this point in order to re-move the salt, to wash it, to add the washings to the liquor, and then to transmit the gasfreely through the solution. As the operation advances, less muriate of potash is formed,and at length nothing but the pure chlorate is separated in crystals. When finally thebubbles of gas pass through without being sensibly absorbed, the process is known to b ecompleted; the liquid may then be allowed to settle, and be poured off from the crystalsof chlorate of potash, which are purified from the muriate by dissolving them in th reetimes their weight of boiling water, and filtering the solution while hot. On its coolm?>the chlorate will separate in pearly-looking crystalline plates. It may be rendered quitepure by a second crystallization, in which state it does not affect solution of nitrate of silver-

The above potash ley usually gets a reddish tint in the course of the process in conse-quence of a little manganesic acid coming over -with the chlorine, but it gradually lose'this color as the saturation becomes complete, when the solution turns yellow. •*-tubes for conveying the gas should be of large diameter, if they be plunged into msaline solution, because the crystallization which takes place in it is apt to choke theup. This inconvenience may however be obviated by attaching to the end of the gtube, a tube of caoutchouc terminated in a small glass funnel, or simply the neck 0 ^caoutchouc bottle with a part of its body, whose width will not be readily closed wtsaline crust. The residuary lixivium may be used against another operation, or it ®be evaporated down to half its bulk and set aside to crystallize, whereby some mchlorate will be obtained, mixed indeed with muriate and carbonate, from which e( jit may be separated by a second crystallization. In general the pure chlorate oWa L n£rdoes not exceed one tenth the weight of the potash employed; because in thus tie ® „gpotash with chlorine, five sixths of it are converted into muriate of potash and on J rsixth into chlorate, and a part of the latter adheres to the muriate, or is lost in the mwaters of the crystallizations. ; n

The chlorate of potash may be more conveniently manufactured, like that ol > j nthe dry way. St. Romer patented at Vienna the following method for that V'ffi - zel },1821 : — Ten pounds of crystallized peroxyde of manganese are to be finely pu t j, emixed with ten pounds of plumbago, and thirty pounds of common salt, and put