Descriptive Chemistry (Paperback)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER VIII. ACIDS, BASES, AND SALTS. Introduction. ? Many chemical compounds fall naturally into one of three groups, long known as acids, bases, and salts. Not all compounds, of course, are included in this classification. Each group has its characteristic properties, though the groups are closely related and sometimes ovex- lap. Many familiar substances belong to these groups. A knowledge of the properties of acids, bases, and salts, of their special behavior, and of their intimate relations is essential in the study of chemistry. General Properties of Acids, Bases, and Salts. ? Acids have a sour taste. The early chemists detected this property, and the word acid (from the Latin acidus, sour) emphasizes the fact. Acids change the color of many vegetable substances. Thus, blue litmus is turned red by acids. Acids also have the power to decompose most carbonates, like limestone, thereby liberating carbon dioxide gas which escapes with effervescence. Most bases have a slimy, soapy feeling, and a bitter taste. They turn red litmus blue. Caustic soda and ammonium hydroxide are bases. Many salts have the well-known salty taste. Sodium chloride, the familiar table salt, is an example. Usually, they have no action on litmus. All acids contain hydrogen, which is usually liberated when metals and acids interact. Most acids contain oxygen. For many years it was thought that oxygen was anessential component of all acids, and its name, oxygen (derived from Greek words meaning " acid producer ") was given by Lavoisier because of this belief (see Discovery of Oxygen). We now know that hydrogen, not oxygen, is the essential component of all acids. Another necessary component of acids is some element like nitrogen, sulphur, chlorine, or phosphorus, which belongs to a class of elem...