TINDER BOXES AND MATCHES. 217 



when a drop of oil of vitriol comes in contact with it, the reason 

 for which is that the sulphuric acid sets free from the potassium 

 chlorate a substance termed chloric acid (just as it sets free nitric 

 acid from potassium nitrate Expt. 270) which acts in such an 

 energetic fashion upon sugar that enough heat is produced to set 

 fire to the whole mass. One of the earliest forms of match for 

 striking a light without using flint and steel with tinder box * con- 

 sisted of a splinter of wood tipped with sulphur and with the end 

 tied up in a little bag containing a small quantity of the mixture 

 of potassium chlorate and sugar, and a small hollow glass ball 

 containing a drop of oil of vitriol and hermetically sealed ; when 

 a light was required the end of the match was struck with a 

 hammer, &c. so as to break the glass ball; the acid coming in 

 contact with the mixture set fire to it, and consequently lit the 

 sulphur match. The numerous accidents occasioned by this kind 

 of matches prevented their ever being extensively used. 



Conjurors often use this action as an illusion, fire being produced 

 by touching objects with a magic rod ; the rod is tipped with glass 

 with a drop of oil of vitriol at the end, and the object has a little 

 of the potassium chlorate and sugar mixture applied to it. 



Caution. Be extremely careful lest the oil of vitriol should 

 drop off the glass rod or be otherwise spilt, as it is excessively 

 corrosive. 



Expt. 257. Potassium Chlorate burning in Hydrogen or 

 Coal gas. Just as a candle will burn brightly in a jar of oxygen 

 because the wax is so far heated as to give off vaporous matter 

 analogous to coal gas, which unites with the oxygen, producing 

 heat, thus keeping up the formation of vaporous matter and 

 maintaining the action ; so can substances capable of giving off 

 oxygen take fire and burn in an atmosphere of hydrogen or coal 

 gas. Fig. 94 represents an arrangement whereby this can be 

 demonstrated. A piece of wide glass tubing (a lamp chimney will 

 answer well) is fitted at the lower end with a perforated cork 

 through which a rapid supply of hydrogen is admitted from a 

 large generator, or of coal gas from the gas main ; the upper part 

 is loosely covered with a piece of tinplate forming a sort of lid, 



* Before the invention of matches, when a light was required a quantity 

 of "tinder" had to be prepared, consisting of linen rags fired in a pan 

 partially covered up, so as to smother the combustion, all air being carefully 

 excluded when the flame ceased, leaving a carbonised mass. A spark being 

 struck by means of flint and steel, and received on tinder thus made and con- 

 tained in a small box, would cause the tinder to take fire ; by blowing care- 

 fully the glowing portion of the tinder would become larger and hot enough to 

 light a sulphur-tipped splinter of wood ; when this was done the tinder box 

 lid was closely shut so as to extinguish the glow. 



