582 SALTPETRE SALTS ings are the city hall, costing $70,000, used as the territorial capitol ; the tabernacle, capable of seating about 15,000 persons, covered by a self-supporting roof ; and the Mormon temple, in course of construction, estimated to cost $10,000,000. The theatre is very large. The government is vested in a mayor and common council, but they are really controlled by the president of the Mormon church. Recently tf m. of street railroad have been built and gas works have been put in operation. The laying of about 5 m. of water pipes is in progress (1875). The city contains two national banks, a savings institution, and three private banks. There are no public schools, but many good private ones. The principal institutions of learning are the university of Deseret (Mor- mon), St. Mark's school (Episcopal), a Roman Catholic nunnery, and the Methodist and Pres- byterian schools. There is a public library, under the auspices of the ladies of the city. Three daily (two Mormon and one gentile) and five weekly (two Scandinavian) news- papers and two monthly periodicals (devoted to religion and education) are published. A miners' hospital is supported mainly by the mining camp near the city. There are about 30 churches, of which all but 6 are Mormon. Salt Lake City was settled in 1847 by the Mor- mons, under the lead of Brigham Young. SALTPETRE. See NITRATES. SILTS. In the present state of chemical science a satisfactory definition of the term salt cannot be given. The older chemists re- garded a salt as a product of the " union " of an acid with a base, as when (using the older notation, as well as atomic weights) nitric acid (NO) unites with potash (KO) to form nitrate of potash (KO,NO) ; and this defini- tion is often used at the present time, but ac- cording to modern theory it is not strictly cor- rect. To say that a salt is produced by the "action" of an acid on a base is correct as far as it goes, but salts are sometimes formed by the direct union of two elements, neither of which is an acid or a base. By the term base is meant a body composed of two or more elements (inorganic bases usually having only two), most frequently an oxide of a metal, which is capable of effecting a double decomposition with an acid, during which water and a salt are formed by the exchange of elements, as when oxide of silver is acted upon by nitric acid (Ag a O + 2HNO,=2AgNO, + H,O), where the oxygen of the oxide of silver unites with the hydrogen of the nitric acid to form water, while the metallic basyle silver unites with the radical (XO S ) to form nitrate of silver. This is a different action from that formerly sup- posed to take place, that is, the direct union of the base and acid, without double decom- position ; for instance, using the old notation and equivalent numbers, AgO + NO B =AgO, NO. That part of the base which unites with a portion of the acid to form the salt is usu- ally called the basyle. In the formation of nitrate of silver above described, the basyle Ag of the base Ag a O displaces the hydrogen which in the nitric acid is united with the radical NOs. Lavoisier supposed that all true acids contained oxygen, and gave the name (meaning acid generator) to that element in accordance with that hypothesis. The term acid was applied to both the anhydrides and their compounds with water, which latter are now regarded as the only true acids. In course of time it was discovered that there were acids containing no oxygen, such as hydrochloric, hydriodic, and hydrobromic acids, which pos- sessed all the other characteristics of Lavoi- sier's acids, as sourness to the taste and the power to redden vegetable blues. This led to the division into oxyacids and hydracids; but it was found that the constitution of common salt was simply binary, it being composed of the metallic basyle sodium united to the ele- ment chlorine, and having the formula NaCl. Berzelius then propounded the theory that a salt consisted of an electro-positive body uni- ted to an electro-negative body, each of which might be either simple or compound. "When simple, as in common salt, they formed haloid salts, so named from their resemblance to com- mon salt (Gr. dXf, sea salt), and consisted of an electro-positive metal united to an electro-neg- ative radical or halogen. When these bodies were compound they formed amphide salts, and these amphide salts might contain oxygen in both base and acid, or they might contain sul- phur in both ; in one case being called oxy- salts, and in the other sulpho-salts. The ha- loid salts were strictly binary compounds, but the amphide salts were regarded as ternary. Davy and Dulong also introduced a theory by which the seeming difference between oxyacid and hydracid salts was reconciled. This was called the binary theory, and it regarded all hydrated acids as in reality salts, containing hydrogen in place of a metal, and acting the part of a basyle toward a single element or group of elements, and all salts as being built up on the type of chloride of sodium. Thus sulphuric acid, HaSO 4 , may be regarded as a salt similar in constitution to potassio sulphate, KjSO-4, the only difference being the presence of the feeble basyle hydrogen in place of the powerful basyle potassium. By the ac- tion of sulphuric acid on zinc there is simply displacement of hydrogen by zinc (H 9 S()4 + Zn=ZnSO 4 -l-2II), hydrogen being evolved in a gaseous state. According to the old ideas, using the old notation, sulphuric acid, H s O,SOi, acting on the zinc, caused electric polarization, by which the affinity of the metal for oxygen was so increased that it rapidly decomposed water, liberating the hydrogen, forming a base, ZnO, with the oxygen, and then uniting with the anhydride SO 3 , forming sulphate of zinc, ZnO,SO s . The binary theory, it will be ob- served, simplifies the reactions, at the same time that it admits of the agency of the elec- tro-motive force; for in the composition of
