458 POTASSIUM. 



A portion of the potash is always "converted into sulphate of 

 potash, which must interfere with the exactness of this decom- 

 position. Blasting powder is composed of 20 sulphur, 15 char- 

 coal, and 65 nitre ; the proportion of sulphur being increased, 

 by which a more powerfully explosive mixture is obtained, but 

 which is not suitable for fire-arms, as they are injured by an 

 excess of sulphur. The most inflammable charcoal is employed 

 in making gunpowder ; which is obtained by calcining branches 

 of about 3-4ths of an inch in diameter, in an iron retort, for a 

 considerable time, at a heat scarcely amounting to redness, and 

 which has a brown colour without lustre. The granulation of 

 gunpowder increases its explosive force. A charge is thus made 

 sufficiently porous to allow flame to penetrate it, and to kindle 

 every grain composing it at the same time. But still the dis- 

 charge of gunpowder is not absolutely instantaneous ; and it is 

 remarkable that other explosive compounds which burn more 

 rapidly than gunpowder, such as fulminating mercury, are not 

 adapted for the movement of projectiles. Their action in ex- 

 ploding is violent but local ; if substituted for gunpowder in 

 charging ordinary fire-arms, they would shatter them to pieces, 

 and riot project the ball. It is a common practise to mix with 

 the charge of blasting powder, used in mining, several times its 

 bulk of sawdust, which renders the combustion of the powder 

 still slower, but productive of a sustained effort, most effectual 

 in moving large masses. 



Chlorate of potash ; KO,C1O 5 ; 1532.6 or 122.81. This salt 

 is the result of a reaction between chlorine and potash, which 

 has already been explained (page 369.) In the preparation of 

 chlorate of potash a strong solution of two or three pounds of 

 carbonate of potash is made, and chlorine passed through it. 

 The gas is conducted into the liquid by a pretty wide tube, or 

 better by a tube terminated by a funnel, to prevent its being 

 choked by the solid salt which is formed. A stage in the pro- 

 cess can be observed, before the liquid has discharged much car- 

 bonic acid, when bicarbonate, chlorate, and hypochlorite of 

 potash exist together in solution, and a considerable quantity 

 of chloride of potassium is deposited. The latter salt is removed, 

 and the current of chlorine continued till the liquid, which is 

 often red from hyperrnanganic acid, becomes colourless or 

 yellow, and ceases to absorb the gas. A considerable quantity 

 of chlorate of potash is deposited in tabular shining crystals 



