12a RUSTING Take 7 test tubes and 11 clean nails Prepare the tubes as shown below Tube 1 Put 2 clean nails in the testtube and half cover them with distilled water These nails are in contact with air and water and form the control experiment Tube 2 Put a few pieces of anhydrous calcium chloride or silica gel in the bottom of a dry testtube and also two nails Put a plug of cotton wool in the top of the tube These nails are in contact with air but not moisture Tube 3 Boil water for several minutes to expel dissolved air and pour into the testtube whilst hot Put 2 nails in the water Put a little Vaseline or a few drops of olive oil on the surface of the hot water The Vaseline will melt and form an airtight layer solidifying as the watercools These nails are in contact with water but not air Tube 4 Half cover 2 nails with water containing a little common salt dissolved in it These nails are in contact with air water and salt Tube 5 Wrap a piece of zinc foil round part of a nail Put the nail in the testtube and almost cover with tap water Tube 6 Wrap a piece of tin foil round part of the nail Put the nail in the testtube and add tap water as you did for tube 5 Tube 7 Wrap a piece of copper wire round a nail and put it in the testtube exactly like tubes 5 and 6 Stand these 7 test tubes in a rack and leave for several days Note the conditions for rusting and which metal zinc copper or tin is best at preventing rusting