METALS Aluminium Al. Antimony (_Stibium_) Sb. Barium Ba. Bismuth Bi. Cadmium Cd. Calcium Ca. Chromium Cr. Copper (_Cuprum_) Cu. Gold (_Aurum_) Au. Iron (_Ferrum_) Fe. Lead (_Plumbum_) Pb. Lithium Li. Magnesium Mg. Manganese Mn. Mercury (_Hydrargyrum_) Hg. Nickel Ni. Platinum Pt. Potassium (_Kalium_) K. Silver (_Argentum_) Ag. Sodium (_Natrium_) Na. Strontium Sr. Tin (_Stannum_) Sn. Zinc Zn. NON-METALS Boron B. Bromine Br. Carbon C. Chlorine Cl. Fluorine F. Hydrogen H. Iodine I. Nitrogen N. Oxygen O. Phosphorus P. Silicon Si. Sulphur S. The first step in the building-up process consists of the union of a metallic with a non-metallic element. Such compounds are binary compounds, and are distinguished by the termination -ide added to the name of the non-metallic element; for example, copper and oxygen unite to form copper oxide, sodium and chlorine form sodium chloride, iron and sulphur form iron sulphide or sulphide of iron. A compound containing more than two elements is distinguished by the termination -ate. Most salts fall within this category; thus we speak of acetate of lead and chlorate of potash, also of sodium sulphate and copper sulphate, the latter form being the more correct. A difficulty arises when two bodies are composed of the same elements combined in different proportions. Then we have to resort to other distinguishing prefixes or suffixes. For this reason we meet with sulphur_ous_ acid and sulphur_ic_ acid, the corresponding salts being sulph_ites_ and sulph_ates_. Crystals and Water of Crystallization. When a soluble salt is to be recovered from its solution, the latter is reduced in bulk by evaporation until, either by experience or by trial, it becomes evident that the solid will be formed as the liquid cools. In some cases, when time is not an important factor, evaporation is left to take place naturally. Under either set of conditions, the substance generally separates out in particles which have a definite geometrical form. These are spoken of as crystals.