„ 13.32 11 91 11 „ 15.37 11 15 15 , 24.43 – 8.44 15 11 „ 35.02 12.05 59 59 91 „ 49.08 51 /1 18.96 , 74.89 35.40 „ 104'78 60.24 19 15 Forrnerly ehlorate of potash was obtained only by passing a stream of ehlorine gas iuta solution of caustic potash, or the carbonate. The liquors w ere concentrated and cooled, when eolourless crystals of ehlorate separated out. The process adopted uow is to pass chlorine gas iuto a mixture of milk of limo and chloride of potassium, contained in strong iron vessels fitttil with agitating gear. Usually, these vessels are about 7 ft. in diameter by 7 ft. deep. A considerable degree of heat is generated, and ehlorate of potassium and chloride of calcium are formed. The liquors are run off and crystallized in iron ve-,sels, m lien the chlorate separates out and chloride of calcium remains in solution. The first crop of crystals i9 removed and placed iu lead-lined tanks, where it is rcdi,solved in boiling water, the necessary temperature bciog obtained by passing in steam. The solution is then run into shallow vtssels and recrystallized. A very pure article may be made by this process, although, since great care is needed, there is a good deal of difference between the various brands. It should consist of nearly pure chlorate, the only impurity being about 0.25 per cent. of chloride and moisture.
This process is usually worked in conneetion with the " decomposing " section of the Le Blanc soda manufacture, and takes the place of, or is carried on concurrently w ith, the bleaching powder process. The chlorine is generated hy the action of hydrochloric acid upon binoxide of manganese. The latter, in weight varying from two to five c‘N t., is placed in stills of greatly varyiug shapes, but always constructed of stone, preferably Yorkshire flags, carefully dressed and bound up with strong iron girders. Hydrochloric acid is run in, at a specific glavity of about 28' Twa., and steam introdueed through a pipe passing through the cover of the still, and reaching below the level of the liquor. Chlorine gas is generated, and conducted away through earthenware pipes fixed in the cover, a mixture of chloride of manganese and iron being left in solution. A more detailed description of this part of the process will be given under the head of Bleaching Powder. It is usual now to recover the manganese from the " still liquors " by Weldon's patent proces.i, for a full deseription of which the reader is also referred tu the same article.
A third method of preparation is by heating ehlerate of calcium with chloride of potassium, thus:— Ca2C103 2KC1 = CaC12 213.C103.
Chlorate of potash forms a well-known source of oxygen gas, and this property of readily yielding up its oxygen makes it valuable for many purposes. It is largely used in calico printing, as an oxidizer ; oalieo prepared with a solution of it saves time in ageing ; a mixture of it with arsenite of soda is used to facilitate the fixing of iron mordants: it is also employed in some steam colours in low-class reds frorn Japan wood, in steam chocolates and blacks. Together with
phosphorus this salt enters largely into the manufacture of matches, and especially "safety '' rnatehes; it is used in the production of fireworks and detonators for exploding dynamite. Finally, it enters into eertain medicinal preparations.
About 3500 tons of ehlorate are produced annually, the chief seats of the industry being in Lancashire, on the Tyne, and at Gla.sgow. The average price is about 10d. per lb.
Chloride of Potassium. (Fa., Chlorure de Potasse ; GER., Chlorhalium.) Synonyms, muriate of potash, digestive salts, sal febralugum Sylvii. Formula, KCL—This salt closely resembles ordinary chloride of sodium. It forms colourless, anhydrous crystals of a cubic form, and a saline and slightly bitter taste, which decrepitate when heated, fuse at a high temperature, and completely volatilize at a strong heat. Chloride of potassium is soluble in three parts of cold water, the solubility increasing with an increase of temperature ; thus at it dissolves in parts of water ; at 13.8°, in 2.87 parts ; at 15.6°, 2.85 parts. The following table exhibits the percentage of the salt in aqueous solutions of different densities, and at 15° :— Chloride of potash occurs native, sometimes pure, but more usually in combination with other metallic chlorides, and forming double salts ; e. g. chloride of potassium and magnesium. Pure native chloride is called "sylvine," and occurs in the well-known beds of Stassfurth, near Magde burg; also in Vesuvius. accompanied by deposits of "kremersite," a mixture of various chlorides of sodium, ammonium, and iron. The chloride of potassium and magnesium is called carnallite, and is perhaps the best known of all these potassic minerals. They have about the following composition :— Carnallite.
Chloride of potassium 24.27 „ magnesium .. 30.98 sodium .. 4.82 calcium 2.82 Sulphate of calcium .. magnesium .. .. trace Oxide of iron .. Chloride of potash may be obtained by burning the metal potassium in dry chlorine gas; by heating it in hydrochloric acid gas ; by dissolving caustic potash, or the carbonate, in aqueous hydrochloric acid, or by the action of potassium upon various metallic chlorides. Usually, how ever, it is prepared by one of four principal methods :—(1) from the potassic minerals of which mention has been already made ; (2) from the ashes of marine plants; (3) from sea-water and brine springs ; (4) as a bye-product in the treatment of beet-root molasses.