Aluminum (Al) Carbon (C) Charcoal, diamonds, graphite (the lead in a pencil is graphite), hard coal, and soot are all made of carbon. Chlorine (Cl) A poison gas that was used in the war. Copper (Cu) Gold (Au) Hydrogen (H) The lightest gas in the world; you got it from water in the last experiment and will get it from an acid in the next. Iodine (I) It is a solid; what you use is iodine dissolved in alcohol. Iron (Fe) Lead (Pb) Mercury (Hg) This is another name for quicksilver. Nickel (Ni) Nitrogen (N) About four fifths of the air is pure nitrogen. Oxygen (O) This is the part of the air we use in breathing. You got some out of water, and you will have it to deal with in another experiment. Phosphorus (P) Phosphorus makes matches glow in the dark, and it makes them strike easily. Platinum (Pt) Radium (Ra) Silver (Ag) Sodium (Na) You are not acquainted with sodium by itself, but when it is combined with the poison gas, chlorine, it makes ordinary table salt. Sulfur (S) Tin (Sn) Zinc (Zn) For the rest of the elements you can refer to any textbook on chemistry. HOW ELEMENTS HIDE IN COMPOUNDS. One strange thing about an element is that it can hide so completely, by combining with another element, that you would never know it was present unless you took the combination apart. Take the black element carbon, for instance. Sugar is made entirely of carbon and water. You can tell this by making sugar very hot. When it is hot enough, it turns black; the water part is driven off and the carbon is left behind. Yet to look at dry, white sugar, or to taste its sweetness, one would never suspect that it was made of pure black, tasteless carbon and colorless, tasteless water. Mixing carbon and water would never give you sugar. But combining them in the right proportions into a chemical compound does produce sugar. Not only is carbon concealed in sugar, but it is present in all plant and animal matter. That is why burning almost any kind of food makes it black. You drive off most of the other elements and separate the food into its parts by getting it too hot; the water evaporates and so does the nitrogen; what is left is mainly black carbon.