30. Q. What does the two-fold character of chemical study involve? A. First, the examination of elementary substances and their compounds. Second, a consideration of the many general and special laws and forces which determine the various possible combinations.
31. Q. How many elementary substances are there now generally recognized as such? A. Sixty-six.
32. Q. About how many of the elements possess names that are familiar to ordinary readers? A. About one sixth of them.
33. Q. Of what two elementary substances is it probable that three fourths of our globe is composed? A. Of oxygen one half, and of silicon one fourth.
34. Q. What general name is given to most of the elements? A. Metals.
35. Q. What symbol and what weight has each element? A. An atomic symbol and an atomic weight.
36. Q. How is an atom of each elementary substance designated? A. By a symbol, usually the initial letter of the native or Latin name of the substance.
37. Q. What are three properties an elementary substance accepted as a metal should possess? A. It must possess the property of existing in a solid condition; it should possess the metallic luster; and it should possess the power and tendency to readily form a chemical union with oxygen.
38. Q. What are called binary and what ternary compounds? A. Compounds having only two kinds of elements are called binaries. Compounds having three kinds of elements are called ternaries.
39. Q. What four binary compounds are given as examples? A. Hydric chloride, sulphur di-oxide, sulphur tri-oxide, and plumbic oxide.