778 CHLORATE OF POTASH 



[For the physiological action of chloral and its hydrate, see Dr. Eichardson's 

 Reports presented to the British Association in 1869, 1870 and 1871]. F. W. E. 



CHXiORAXiUM. Under this name a solution of chloride of aluminium has been 

 introduced as an antiseptic and disinfectant. It is prepared in the form of a liquid of 

 definite strength, and as a powder. Cotton-wool containing a certain per-centage of 

 chloralum is made for the use of tho surgeon. 



CHLORANILINE. C 12 H 8 C1N (CH 8 CW). An organic base obtained by 

 distilling chlorisatin with a concentrated solution of caustic potash. It forms with 

 acids a series of definite well-crystallised salts. 



CHLORATE OF POTASH, or CHX.ORA.Tfi OF POTASSIUM, formerly 

 called oxymuriate of potash. KO.C10 S (S:C1O 3 ). This important salt has become 

 the object of a pretty extensive manufacture, in consequence of its use in the prepara- 

 tion of lucifer matches, as a constituent of white gunpowder and certain mixtures 

 used in pyrotechny, and as an ingredient in some of the detonating compounds for the 

 cartridges of needle-guns ; the chlorate is also used i a calico-printing and in the 

 preparation of certain aniline colours, while the chemist frequently employs it as a 

 convenient oxidising agent and as a source of free oxygen gas. To supply these 

 demands, about 750 tons of the salt, valued at nearly 80.000J. are annually produced 

 in this country. 



Chlorate of potash was formerly prepared by transmitting an excess of chlorine gas 

 through a solution of potash, whereby a mixture of chlorate of potash and chloride of 

 potassium was obtained, the former salt being readily separated from the latter by its 

 sparing solubility in water. 



Having made a strong solution of purified potash, or carbonate of potash, with from 

 2 to 3 parts of water, a current of chlorine gas is passed through it in a Woulfe's 

 apparatus, till it ceases to absorb anymore. 'Chloride of potash' and chloride of 

 potassium alone 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 (that is, till the potash is about one half saturated with chlorine, as 

 indicated by litmus-paper ceasing to be darkened and beginning to be blanched), only 

 the chloride of potassium or muriate of potash falls. The process should be inter- 

 rupted at this point in order to remove the salt, to wash it, to add the washings to 

 the liquor, and then to transmit the gas freely 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, the bubbles of gas pass through 

 without being sensibly absorbed, the process is known to be completed ; the liquid 

 may then be allowed to settle, and be poured off from the crystals of chlorate of 

 potash, which are purified from the muriate by dissolving them in three times their 

 weight of boiling water and filtering the solution while hot. On its cooling, the 

 chlorate will separate in pearly-crystalline plates. It may be rendered quite puro 

 by a second crystallisation, 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 con- 

 sequence of a little manganesic acid coming over with the chlorine, but it gradually 

 loses this colour as the saturation becomes complete, and then the solution turns yellow. 

 The tubes for conveying the gas should be of large diameter, if they be plunged into 

 the saline solution, because the crystallisation which takes place in it is apt to choke 

 them up. This inconvenience may, however, be obviated by attaching to the end of 

 the glass tube a tube of caoutchouc terminated in a small glass funnel, or simply the 

 neck of a caoutchouc bottle with a part of its body, whose width will not be readily 

 closed with a saline crust. The residuary lixivium may be used in another operation, 

 or it may be evaporated down to half its bulk and set aside to crystallise, whereby 

 some more chlorate will be obtained, mixed indeed with muriate and carbonate, from 

 which, however, it may be separated by a second crystallisation. In general the pure 

 chlorate obtained does not exceed yLth the weight of the potash employed ; because in 

 thus treating potash with chlorine, |ths of it are converted into muriate of potash and 

 only th into chlorate, and a part of the latter adheres to the muriate, or is lost in 

 the mother-waters of the crystallisation. 



In 1821 St. Homer patented at Vienna the following method for preparing chlorate 

 of potash by the dry way : Ten pounds of crystallised peroxide of manganese are 

 to be finely pulverised, mixed with 10 pounds of plumbago, and 30 pounds of common 

 salt, and put into the leaden retort represented \nfig. 460, p. 783. From the middle 

 of tho helmet-shaped lid of this vessel, a lead tube, 2 feet long and 2 inches wide, 

 conducts to the receiver, which is a square earthen, pan, hard glazed both within and 

 without, of the same capacity with the retort. The end of the tube must be made 

 fast to a frame at tho height of 6 inches above the bottom of the receiver. Upon its 



