40. Q. Under what two heads are the principal ternaries grouped? A. Acids and salts.
41. Q. What are the two principal ternary acids used by chemists? A. Nitric acid and sulphuric acid.
42. Q. What is meant by the term atom? A. It is that portion of any kind of matter that is to human beings indivisible in fact.
43. Q. With what invisible, occult power is each atom and each molecule endowed? A. A power called chemical affinity.
44. Q. What are three of the peculiarities of chemical affinity? A. Each kind of atom has its peculiar chemical affinities. Each atom has a certain equivalence or atom-fixing power. Chemical changes produce striking results.
45. Q. What is the most common way of producing hydrogen? A. By bringing together sulphuric acid and zinc.
46. Q. What are some of the properties of hydrogen as a gas? A. It is colorless, odorless, tasteless, and, bulk for bulk, it is the lightest substance known in nature.
47. Q. What is the most interesting chemical property of hydrogen? A. Its power to unite with oxygen.
48. Q. What is said of the uses to which hydrogen may be put? A. As an elementary gas it finds but few applications in the arts.
49. Q. For what standards is hydrogen used by chemists? A. As the standard of equivalence or atom-fixing power; the standard of atomic weight, and the standard of density for gases.