REATIVE SCIENCE. 



161 



RECREATIVE SCIENCE. I. 



.Hi; S.U ICM <>F l.K.HT. 



PROPOS of shining lights, intellectual an well as material, and 

 way of inaugurating the series of papers on " Recreative 

 ' useless to the reader unless accompanied with ample 

 iptions of the mode of conducting scientific experiments, 

 k we first of the late prince of manipulators, the much- 

 loved and regretted Faraday, to whom a " memorial " is now 

 course of promotion in the shape of a monument in St. Paul's 

 .1. It may bo said, without exaggeration, that if 

 indon had not contained a single philosophical instrument 

 !-. this ingenious, original, and skilful philosopher would 

 ,ve made himself understood by experiments and manipula- 

 ns, all conducted with what might be called the barest ncces- 

 ios. Tyndall states, in his lecture "On Faraday as a Disco- 

 T," that years ago, when Faraday assisted Mr. Brando in 

 .is lectures, he did this so quietly, skilfully, and modestly, that 

 his master's vocation was pronounced to be " lecturing on velvet." 

 Had Faraday been a clumsy, slovenly, and careless manipulator, 

 his position in life might have been quite different from that 

 hich he justly held ; but Faraday was industrious and pains- 

 ing to the last degree, and has left a bright example for all 

 uld-be philosophers to imitate. 



Beginning with the artificial means of procuring light, there 

 no substance that can surpass phosphorus in this respect ; as 

 its name implies, it is a "light-bearer" (<u>y, light, and tytpftv, to 

 bear), and, at a cost of a few pence, may afford hours of amuse- 

 ment and instruction to those who will experiment carefully 

 with it. Phosphorus is always kept under water, and thus 

 viewed in its containing phial, gives no sign of light when exa- 

 mined in a darkened room. 



A stick of phosphorus may be cut up into small pieces under 

 water in a saucer, and still no light is apparent. With the 

 sharp point of a knife or a pointed wire a little bit is taken out 

 of the water and gently squeezed in the folds of a cotton duster, 

 to remove the moisture which adheres to it. The phosphorus 

 now gradually combines with the oxygen of the air. A sponta- 

 neous though slow combustion is set up, and it emits a faint, 

 pale-green coloured light ; a white smoke, called phosphorous 

 acid, is at the same time produced, and this, by exposure to 

 air containing moisture, changes to phosphoric acid. To show 

 that acid is produced whilst the phosphorus is shining, place 

 a small portion in a short length of glass tube, narrowed at one 

 end to prevent the bit of phosphorus tumbling out, after it is 

 reduced in size by oxidation. Put the tube in a little glass 

 funnel, supported in a wine-glass to receive the dense acid 

 liquor which will gradually form and drop into it. The first 

 acid generated is termed phosphorous acid, and as this attracts 

 moisture from the air, and is what is called deliquescent, it 

 gradually takes up more oxygen, and is converted into phos- 

 phoric acid. 



The fluid obtained by the above process diluted with a little 

 water is found to be strongly acid to the taste ; it will redden a 

 piece of paper coloured blue with tincture of litmus ; and if 

 a few grains of carbonate of soda are dropped carefully into the 

 glass, they effervesce, in consequence of the escape of carbonic 

 acid produced by the combination of tho acid with the alkaline 

 base. These experiments, conducted on the smallest scale, 

 indicate to the operator the cause of the production of the light 

 from the phosphorus ; and the principle being once understood, 

 it is easy to modify the manner of oxidation. 



To show the oxidation of phosphorus under water, and tho 

 evolution of light under these apparently contradictory and 

 exceptional circumstances, a few grains of chlorate of potash 

 and some little bits of phosphorus are placed with water in a 

 dseper vessel, such as an ale or, better still, a champagne glass. 

 When oil of vitriol is poured slowly down one side of tho glass, 

 or conveyed to tho materials by a glass or pewter tube with a 

 funnel-like opening at tho top, beautiful flashes of green light 

 are observed, and the energy of the change is shown by a peculiar 

 crackling sound produced by the explosion under water of the 

 little bubbles of peroxide of chlorine, which are resolved into 

 oxygen and chlorine, ind cause the submerged phosphorus to 

 burn when it comes in contact with them. Tiny particles of 

 hosphorus are sometimes enclosed in the bubbles of the mixed 



is, and they burn as they ascend. 

 A few pieces of phosphorus thrown into a clean Florence oil- 



89 N.E. 



flask half full of water, will exhibit a display of miniature bomb* 

 and rockets in the space above the water when the latter it 

 boiled. A lambent flame makes iU appearance at the mouth ot 

 the flask, consisting of finely divided and sublimed phosphorus, 

 mixed with steam, which slowly unites with the oxygen of the 

 air, as the vapour is condensed into water. 



Phosphorus quickly dissolves in bisulphide of carbon ; and if 

 the solution is dropped upon a sheet of blotting paper the 

 solvent viz., the bisulphide of carbon evaporates, and the finely 

 divided phosphorus left in the pores of the paper unites rapidly 

 with the oxygen of the air, and, being in large quantity, first 

 shines with a green light, and then burns moat brilliantly, and 

 contrasts in a very marked degree with the feeble light obtained 

 when phosphorus is boiled in water and allowed to escape with 

 tho steam from the month of a flask. 



Of course the proper apparatus, a ring-stand for holding a 

 flask with its contents, and a convenient heat-giving flame, such 

 as that from a spirit-lamp, or a mixed air and coal-gas burner, 

 are most desirable ; but as these experiments are often ventured 

 on at a moment's notice in some far away country house, it is 

 quite as well to be able to imitate Faraday, and make apparatus 

 out of nothing, as it is termed the nothing being such glass, 

 or other vessels, pots and pans, which the house may afford. 



For the time-honoured ring-stand, a common red garden 

 flower-pot, with a triangular wire resting on the top to carry 

 the flask, and containing a spirit-lamp improvised from part of an 

 ink-bottle filled with methylated spirit, and fitted with a per- 

 forated cork through which some shreds of cotton are passed, 

 will answer the purpose required ; and to prevent the cork 

 burning, a bit of thin sheet-lead may be perforated and laid 

 upon it. The flower-pot protects the flame, and prevents its 

 being blown about, and thereby economises heat, i.e., spirit. The 

 changes thus described denote that chemical action is one of 

 tho most important means of obtaining artificial light; at the 

 samo time it will be understood that tho light-giving power is 

 not confined to experiments with phosphorus. A block of 

 Wenham Lake ice becomes a beautiful source of light if a globule 

 of potassium is placed upon it ; and at an American popular 

 lecture we hear of pounds of the metal potassium thrown upon 

 hundred-weights of ice, producing a blaze of light worthy 

 of the palmy days of Vauxhall. Ice, as everybody is supposed 

 to know, is only a solidified compound of oxygen and hydrogen ; 

 the former unites with tho metal, and generating an enormous 

 amount of heat, becomes red hot, and sets fire to the hydrogen, 

 which escapes around the potassium. A piece of wetted blot- 

 ting-paper laid in a common dinner-plate will always set fire to 

 sodium, and this metal burns with its peculiar monochromatic 

 or yellow light : the experiment fails if the sodium is thrown 

 on water. Young people should take care of their eyes in all 

 experiments with potassium and sodium, by standing at a 

 respectful distance from the burning metals, which usually burst 

 at the last moment when the red-hot globule of fused alkali 

 (potash or soda) comes in contact with the cold ice or water. 

 The red-hot globule of alkali is repelled and supported on a 

 cushion of vapour, and when the temperature falls it touches 

 the water, steam is generated with explosive violence, the 

 globule bursts, and is blown about in all directions. 



The combustion of tallow, oil, wax, and gas affords a practical 

 illustration of tho production of light by chemical action. It 

 does not, however, always follow that the body giving out light 

 burns ; it has, therefore, been necessary to give a different term 

 to this effect, viz., ignition ; and the ignition of solids becomes 

 a source of light that will next be considered. The difference 

 between combustion and ignition is easily demonstrated, by 

 placing a pill-box containing a little gun-cotton in a deep glass 

 filled with carbonic acid. On attempting to explode the gun- 

 cotton with a lighted taper, the latter is of course extinguished, 

 because it will not burn in carbonic acid ; but if a wire is made 

 red-hot, and passed through the gas until it touches the gun- 

 cotton, a flash of light is seen as the cotton is exploded, the 

 ignition of the solid iron being wholly unaffected by circum- 

 stances that prevent combustion. Carbonic acid gas is easily 

 procured by placing a few lumps of chalk, whitening, or marble 

 in a small jug, and pouring vinegar, or dilute sulphuric, hydro- 

 chloric, or nitric acid slowly upon it. Whilst the operation is 

 proceeding a piece of paper should be laid upon the top of the 

 jug to prevent any motion in the carbonic acid thus generated; 

 and by applying a lighted taper occasionally it may soon bo dis- 



