So I was trying a home chemistry experiment with sodium hydroxide and aluminum foilI put a bit of sodium hydroxide in a cup, mixed it with water, and reacted some aluminum foil in itIt left a black residue (which I believe to be carbon from the coating on the foil)I left the cup on the windowsill and when I came back a few days later, the black precipitate was orangeThe cup was glass, if that would mean anythingI know that sodium hydroxide can dissolve that sometimes.
the black precipitate probably oxidized by sitting in the sun and in the open air2 [Al(OH)4]1- (aluminate ion) forms when Al is placed in NaOH if allowed to sit long enough, the Al(OH)4-1 ion may form with the Na+ in solution to make NaAl(OH)4 as the liquid evaporates.
