477 



easily separated from potassium chloride, because it is sparingly soluble 

 in cold water. 37 



If dilute sulphuric acid be added to a solution of potassium chlorate, 

 then chloric <t<-i<l is liberated; but it cannot be separated by distillation, 

 .as it is decomposed in the process. To obtain the free acid sulphuric 

 jicid must be added to a solution of barium chlorate. 38 The sulphuric 

 .acid JLCIVCS a precipitate of barium sulphate with the barium, and free 

 chloric acid remains in solution. The solution may be evaporated 

 under the receiver of an air-pump. This solution is colourless, has no 

 .smell, and acts as a powerful acid (it saturates sodium hydroxide, 

 decomposes sodium carbonate, gives hydrogen with zinc, tfcc.) ; when 



37 If chlorine be passed through a cold solution of potash, then a bleaching compound, 

 potassium chloride and hypochlorite, HC1 + KC1O, is formed, but if it be passed through 

 a hut solution potassium chlorate is formed. As this is sparingly soluble in water, it 

 chokes the gas-conducting tube, which should therefore be widened out at the end. 



Potassium chlorate is usually prepared on a large scale from calcium chlorate, which 

 is prepared by passing chlorine (as long as it is absorbed) into water containing lime, the 

 mixture being kept warm. A mixture of calcium chlorate and chloride is thus formed 

 in the solution. Potassium chloride is then added to the warm solution, and on cooling 

 a precipitation of potassium chlorate is formed as a substance which is sparingly soluble 

 in cold water, especially in the presence of other salts. The double decomposition taking 

 place is Ca( ClO-)o + 2KC1 = CaCL + '2KC1O 3 . On a small scale in the laboratory potassium 

 chlorate is best prepared from a strong solution of bleaching powder by passing chlorine 

 through it and then adding potassium chloride. 



Potassium chlorate crystallises easily in large colourless tabular crystals. Its solu- 

 bility in 100 parts of water at 0= 3 parts, 20= 8 parts, 40= 14 parts, 60= 25 parts, 

 80 = 40 parts. For comparison we will cite the following figures showing the solubility of 

 potassium chloride and perchlorate in 100 parts of water: potassium chloride at 0=28 

 (arts, -JO - = >55 parts, 40 = 40 parts, 100= 57 parts ; potassium perchlorate at about 1 

 >art . -' * about 1 ^ parts, 100 about 18 parts. When heated potassium chlorate melts (the 

 nelting point has been given as from 335-376 ; according to the latest determination by 

 .'arnellev, :'>r> ( .) ) and decomposes with the evolution of oxygen, potassium perchlorate 

 >eing at first formed, as will afterwards be described. A mixture of potassium chlorate 

 and nitric and hydrochloric acids brings about oxidation and chlorination in solutions. 

 It deflagrates when thrown upon incandescent carbon, and when mixed with sulphur ( 

 by weight) it sets light to it, even when struck, in which case an explosion takes place. 

 The same occurs with many metallic sulphides and organic substances. Such mixtures 

 are inflamed by a drop of sulphuric acid. All these effects are due to the large amount 

 of oxygen contained in potassium chlorate, and to the ease with which it is evolved. A 

 mixture of two parts of potassium chlorate, one part of sugar, and one part of yellow 

 prussiate of potash acts like gunpowder, but it burns very rapidly, and therefore bursts 

 the guns, and also it has a very strong oxidising action on their metal. The sodium salt, 

 Na( 1< >.-. is much more soluble than the potassium salt, and it is therefore more difficult 

 to free it from sodium chloride, &c. The barium salt is also more soluble than the 

 potassium salt; 0= 24 parts, 20= 37 parts, 80= 98 parts of salt per 100 of water. 



~ 3 Barium chlorate, Ba(ClO;j)2,HoO, is prepared in the following way : impure chloric 

 acid is first prepared and saturated with baryta, and the barium salt purified by crystal- 

 lisation. The impure free chloric acid is obtained by converting the potassium in potas- 

 sium chlorate into an insoluble salt. This is done by adding tartaric or hydrofluosilicic 

 acid to a solution of potassium chlorate, because potassium tartrate and potassium silico- 

 fluoride are very sparingly soluble in water. Chloric acid is easily soluble in water. 



