118 SCIENTIFIC AMUSEMENTS. 



the magnesia and vinegar, it dissolves, forming not a yellow solu- 

 tion, as might be expected, but a colourless one. If the liquid is 

 not quite clear, it should be filtered (Expt. 56) ; the clear filtered 

 solution may be evaporated in a basin over a water-bath (Expt. 

 89) or small flame until only a little fluid is left ; if this is left 

 awhile white crystals will form, consisting of the substance called 

 nitrate of lead, the nitric acid and the litharge being both altered 

 by the chemical action taking place between them, giving rise to 

 nitrate of lead as the product. 



If you substitute white vinegar for diluted nitric acid in this 

 experiment, you will finally obtain the substance called acetate of 

 had, or " sugar of lead," on account of its sweet taste. Be careful 

 not to swallow this sweet substance in any quantity, as it is poison- 

 ous; when pickles come in contact with lead (as sometimes 

 happens with pickle-bottles covered over with a metal capsule 

 when the metal contains lead), sugar of lead is sometimes formed, 

 by the action of the vinegar on the lead ; so that people par- 

 taking of the pickles are made ill in consequence. 



Oxide of mercury is an orange-red powder ; if you substitute 

 this for litharge, diluted nitric acid will dissolve it, forming not a 

 red, but a colourless fluid, containing the compound termed nitrate 

 of mercury, formed, as in the other cases, in virtue of the chemical 

 action taking place between the acid solvent and the metallic 

 oxide dissolved. 



Expt. Ill To dissolve a Red Solid (Copper) in a Colourless 

 Fluid (Ammonia Water) producing a Blue Solution. Obtain 

 some " spirits of hartshorn " (otherwise called solution of ammonia 

 or liquor ammoniee) and some copper shavings or turnings. Cram 

 these loosely into a bottle, and pour in a teaspoonful or two of the 

 ammonia solution, shaking it about so as to wet the copper there- 

 with ; the liquid will soon assume a beautiful blue colour, owing 

 to the circumstance that, under the conjoined influence of the air 

 in the bottle and the ammonia, a little of the red copper becomes 

 converted into a soluble compound of a blue colour. 



To prove that the presence of air is necessary to make the 

 copper dissolve, fill a small bottle quite full of ammonia solution, 

 and then drop into it some bits of clean bright copper (not dirty 

 or dull on the surface) ; cork the bottle, taking care that there is 

 no air in it, and that it is quite full of liquid. You will find that 

 even after many hours standing the liquid does not become blue 

 (provided the copper is quite bright and all air is excluded). Now 

 pour out most of the liquid, leaving only a few drops, and letting 

 air enter without allowing the bits of copper to fall out. Cork the 

 bottle again, and shake up the contents, and you will see that the 



