CHLORATE OP POTASH 779 



inner side, 4 inches apart, brackets are to be fixed for supporting a series of laths or 

 shelves of white wood on which a number of little paper or pasteboard boxes are to 

 be laid. In these boxes 10 pounds of the purest carbonate of potash, prepared from 

 tartar, are to be spread. The receiver must now be covered with a lid made tight by 

 a water lute. Twenty pounds of concentrated sulphuric acid, previously diluted with 

 1 6 pounds of water, and then cooled, are to be poured upon the mixed materials in 

 the retort, and the lid immediately secured, with the tube adjusted in the receiver. The 

 whole must be allowed to operate spontaneously without heat for 12 hours. At the 

 end of this time the retort is to be surrounded with a water-bath and steadily heated 

 during 12 hours, and then left to cool for 6 hours. The apparatus must now be 

 opened, the cakes of chlorate of potash removed, and freed from muriate by solution 

 and crystallisation. 



Liebig proposed the following process for obtaining chlorate of potash : 



Heat chloride of lime in water till it ceases to destroy vegetable colours. In this 

 case a mixture of chloride of calcium and chlorate of potash is obtained. This is to 

 be dissolved in hot water, and to the solution concentrated by evaporation, chloride 

 of potassium is to be added, and then suffered to cool. After cooling, a quantity of 

 crystals of chlorate of potash is obtained, which are to be redissolved and crystallised 

 again to purify them. Liebig considered that this would be a cheap process for 

 obtaining chlorate of potash. From 12 oz. of chloride of lime, of so bad a quality 

 that is left 65 per cent, of insoluble matter, he obtained an ounce of chlorate of potash. 



The only difficulty to overcome in this process arises from the chloride of lime not 

 being so easily decomposed by heat as is generally supposed ; a solution of it may be 

 kept boiling for an hour without losing its bleaching power. The best method is to 

 form a thin paste with chloride of lime and water, and then to evaporate it to dryness. 

 If it be required to prepare it by passing chlorine into cream of lime, it is advantage- 

 ous to keep it very hot. The chlorate of potash which separates from the solution 

 by cystallisation has not the form of scales which it usually possesses, but is 

 prismatic : whether this is occasioned by some admixture has not been ascertained ; 

 but on recrystallising, it is obtained in the usual form. The solution ought not 

 merely to be left to cool, in order to procure crystals, for the crystallisation is far 

 from being terminated even after complete cooling ; crystals continue to be deposited 

 for 3 or 4 days. 



The following modification of the process for making chlorate of potash is that 

 of M. Ve"e : A solution of chloride of lime marking 18 or 20 Baume is to be set 

 upon the fire in a lead or cast-iron pot, and when it begins to get hot, there is to bo 

 dissolved in it a quantity of chloride of potassium sufficient to raise the hydrometer 

 3 or 4. It must then be concentrated as quickly as possible till it marks 30 or 31, 

 taking care that it does not boil over by the sudden extrication of oxygen. The 

 concentrated liquor is set aside to crystallise in a cool place, when a deposit of 

 chlorate of potash forms, mixed with chloride of potassium. The mother-waters 

 being evaporated to the density of 36, afford another crop of crystals, after which 

 they may be thrown away. The salts obtained at the first crystallisation are to be 

 redissolved, and the solution being brought to 15 or 16 is to be filtered, when it 

 will afford upon cooling pure chlorate of potash. 



The following ingenious and easy way of making this valuable chlorate was sug- 

 gested by the late Professor Graham : Mix equal atomic weights of carbonate of 

 potash and hydrate of lime (70 of the former, if pure, and 37 of slaked lime in 

 powder), diffuse them through cold water, and transmit chlorine gas through the 

 mixture. The gas is absorbed with great avidity, and the production of a boiling 

 heat. When the saturation is complete, carbonate of lime remains, and a mixture of 

 muriate and chlorate of potash, which latter salts are to be separated, as usual, by 

 the difference of their solubity in water. . 



It has been remarked on the above process, that it effects no saving of potassa, and 

 therefore is far inferior to the one long practised in several parts of Germany, espe- 

 cially at Giessen, and introduced into this country a good many years ago by I)r. 

 Wagenmann, from Berlin. The chlorine is passed into a mixture of one equivalent 

 of chloride of potassium (76), and 6 equivalents of hydrate of lime (222), previously 

 stirred with water to the consistence of a thin paste. Thus the calcium of the lime 

 unites with the chlorine to form chloride of calcium, while the chloride of potassium is 

 converted into chlorate of potash, which salt is easily separated in crystals by its 

 sparing solubility. 



Chlorate of potash may also be made by saturating with chlorine a mixture of 

 74 parts of chloride of potassium (muriate of potash) and 168 parts of quicklime, 

 brought to the consistency of a thin pap by the cautious addition of water. The mass 

 being dissolved in warm water, and evaporated and cooled, yields crystals of chlorate 

 of potash, while a mother-water of chloride of calcium (muriate of lime) remains. 



