COLOURED FLAMES. 211 



Expt. 245. Coloured Alcohol Flames. When pure alcohol is 

 burnt the light given out by the flame appears of a blue colour, 

 but has extremely little intensity or illuminating power ; by 

 sprinkling a pinch of common salt on the wick of a spirit lamp 

 the flame is altered in colour to yellow, and is rendered a good 

 deal brighter. The yellow light thus emitted causes many objects 

 seen by its aid to appear entirely different in colour from their 

 ordinary appearance by daylight; brightly tinted dresses or 

 other objects seem dull and grey, and the face assumes a most 

 ghastly hue. A soup plate containing a handful of salt on which 

 a wineglassful of methylated spirit has been poured answers well 

 to develop this kind of colour transformation, the room being 

 otherwise dark ; or large torches may be made by winding tow 

 round broomsticks, and saturating them with spirit mixed up with 

 powdered salt ; or better still, the tow may be first soaked in 

 brine and then dried before winding round the sticks. The effect 

 of illuminating a room full of people with such torches is most 

 remarkable, especially if some one clothed in a white sheet 

 suddenly makes his appearance unexpectedly. 



In a similar fashion red flames may be produced by using 

 powdered nitrate of strontium instead of salt ; and green ones by 

 employing nitrate of barium or boric acid. 



Caution. Care must be taken not to upset the plate containing 

 the alcohol, otherwise a serious accident may easily happen by 

 objects being fired. The plate should be placed on a tea tray so 

 that nothing will be spilt if the plate break with the heat. In the 

 case of torches, it is desirable to wind some copper wire loosely round 

 the tow, so as to prevent any of the strands being burnt through 

 and fragments of blazing tow being dropped in consequence. 



CHAPTER XV. 



CHEMICAL ACTIONS OF RECIPROCAL DECOMPOSITION. 

 Actions resulting in the Evolution of Gas. 



Expt. 246. To produce Hydrogen from Water. Certain 

 substances have the power of acting upon water, bringing about 

 replacement (Chapter I.) of the hydrogen by the substance used ; 

 various metals possess this property, some of them acting energeti- 

 cally upon liquid water or even solid ice, whilst others require the 

 help of a considerable increase of temperature before the action 



