222 SCIENTIFIC AMUSEMENTS. 



not to take too vigorous a sniff at the fumes, otherwise they will 

 almost choke you for the moment) ; or by the turning blue of red- 

 dened litmus paper, or other colour change with appropriate test 

 papers as in Expt. 142. All the experiments with ammonia gas 

 above described may be performed with gas prepared thus, instead 

 of by heating strong solution of ammonia as in Expt. 75. Put half 

 an ounce of slaked lime mixed with as much salammoniac in the 

 flask instead of the strong ammonia cal liquor, and apply heat, col- 

 lecting the gas precisely as before. By leading the gas thus 

 formed into water until the latter has dissolved as much ammonia 

 gas as it can take up, the "liquor ammonise" of commerce is 

 produced \ for the sake of convenience and cheapness, ammonium 

 sulphate is generally used instead of ammonium chloride. 



Reduction of Metals from their Compounds. 



Expt. 264. To obtain Metallic Lead from Oxide of Lead. 



In Expt. 15 we have seen that when molten lead is skimmed bright 

 and then exposed to the air a dull film forms on the surface, and 

 the " dross " thus produced is formed by the combination of the 

 lead with the oxygen of the air, just as magnesium combines with 

 oxygen (Expt. 231), but less energetically. In order to reverse 

 this action and "reduce" metallic lead from oxide of lead, the 

 latter must be heated with some substance that will combine with 

 the oxygen and liberate the lead by an action of single displace- 

 ment. Such a substance is powdered charcoal, if the temperature 

 is high enough, i.e., at a red heat. Mix some litharge, or oxide 

 of lead, with a quarter of its weight of powdered charcoal, and 

 press the mixture into a clay crucible ; heat this red hot in a 

 kitchen fire, the crucible being well covered ; after cooling you 

 will find that more or less of the lead present has melted down to 

 the bottom of the crucible, forming a t( button" of metal. The 

 experiment succeeds better if a little oil or tallow is mixed in with 

 the powder. 



Expt. 265. To obtain Metallic Bismuth from Oxide of Bis- 

 muth and Metallic Tin from Oxide of Tin. Proceed in exactly 

 the same way as in Expt. 264, using oxide of bismuth or oxide of 

 tin instead of oxide of lead ; metallic bismuth or tin respectively 

 will result. 



Expt. 266. To obtain Metallic Antimony from Sulphide of 

 Antimony. Sulphide of antimony consists of antimony combined 

 with sulphur, just as oxide of lead is lead combined with oxygen. 

 Mix powdered sulphide of antimony with half its weight of fine 

 iron filings, and add some cream of tartar (bitartrate of potassium) 



