156 SCIENTIFIC AMUSEMENTS. 



a paper filter and drained from the mother-liquor (Expt. 56), and 

 will then be found to be neutral to litmus test-papers. 



Expt. 166. To dissolve Quicksilver. Introduce a small 

 quantity of mercury into a test-tube (about as much in volume as 

 a small drop of water), and pour over it nitric acid diluted with 

 two or three times its bulk of water, and then warm gently over 

 the lamp. The acid will act on the quicksilver precisely as it did 

 upon copper in Expt. 116, the gas nitric oxide being evolved, and 

 the mercury being gradually dissolved, forming a salt called nitrate 

 of mercury, corresponding with nitrate of copper. 



If mercury be boiled with strong sulphuric acid, much the same 

 kind of change takes place as when copper is similarly treated 

 (Expt. 117) ; sulphur dioxide is evolved, and the mercury becomes 

 converted into sulphate of mercury, a salt much less soluble 

 in water than sulphate of copper, but still not absolutely in- 

 soluble. 



Expt. 167. To dissolve Bromine in Caustic Soda. Bromine 

 is a brownish-red liquid, emitting most suffocating fumes ; in water 

 it dissolves only to a limited extent, but in caustic soda solution 

 it dissolves readily, forming a solution possessing the same bleach- 

 ing properties as chloride of lime, and containing an analogous 

 compound termed hypobromite of sodium. A few drops of this 

 solution added to water tinted with indigo or litmus tincture, will 

 bleach the colour readily like chlorine-water (Expt. 163). 



Expt. 168. To produce Hydrogen by means of Sodium 

 Amalgam. Certain metals will dissolve in hot quicksilver, form- 

 ing solutions termed "amalgams," which often become solid at the 

 ordinary temperature. If a piece of the metal sodium as large as 

 a pea be held in a pair of tongs and plunged underneath half an 

 ounce of warm mercury, the mercury will dissolve the sodium (if 

 its surface is cleaned by scraping previously), generally producing 

 a good deal of heat and some amount of burning of the sodium or 

 "deflagration"; if now the solution of sodium in mercury, or fluid 

 sodium amalgam, be poured into a cup full of water, a chemical 

 action will be set up, resulting in the evolution of bubbles of 

 combustible gas, hydrogen (Expt. 10), and the formation of an 

 alkaline solution (Expt. 142) containing caustic soda, whilst the 

 mercury remains in its original condition. 



Expt. 169. To produce vigorous Combustion by mixing two 

 hot Liquids. In one crucible melt half an ounce of zinc over a 

 good lamp, and in another fuse as much saltpetre (nitrate of 

 potassium). Firmly grip the crucible containing the melted salt- 

 petre with a long pair of two-handed crucible tongs (fig. 68), and 

 pour the liquid saltpetre into the melted zinc ; a vigorous chemical 



