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SYMBOLS AND EQUIVALENTS OE THE ELEMENTS. 77 274. When any two elements combine chemically, it is found that the weights of the two elements are as some low multiples of the numbers, or ‘ equivalents,’ annexed to them in the pre ceding table. Thus one combination of iron and sulphur exists, in which the proportions of the iron and sulphur are as one equivalent, or 350"00 of the former, and one equivalent or 200'00 of the latter; in another combination of the same elements, the pro portions of iron and sulphur are as one equivalent, or 350'00 of the former, and two equivalents, or -lOO'OO of the latter. In one of the compounds of manganese and oxygen, the proportions of manganese and oxygen have been found as one equivalent, or 3-14'41 of manganese, and one equivalent, or 100 of oxygen. In another, as two equivalents, or 688'88 of manganese, and three equivalents, or 300'00 of oxygen. In peroxide of man ganese, as one equivalent, or 344'44 of manganese, and two equivalents, or 200'00 of oxygen. In manganic acid, as one equivalent, or 344'44 of manganese, aud three equivalents, or soo'ooo of oxygen; in permanganic acid, as two equivalents,^ °r 688'88 of manganese, and seven equivalents, or 700'00 of oxygen. A compound of two elements is denoted by the symbols of the two elements ; the number of multiples ol each, when greater than one, being denoted by figures respectively annexed to them. Tims Eos denotes the combination of iron and sulphur, consist ing of one equivalent of each element; Fos a the combination of one equivalent of iron and two equivalents of sulphur ; MnV the com bination of two equivalents of manganese and three of oxygen ; Mno 3 the combination of one equivalent of manganese and three equivalents of oxygen. In order to abbreviate the symbols, equiva lents of oxygen are denoted by dots, one for each equivalent, placed over the symbol of the element with which they are combined; equivalents of sulphur are denoted in like manner by accents. A double equivalent of an element is denoted by its symbol having a dash drawn through it. Tlius Mn denotes MnO 1 , denotes Mn’o 1 , ec denotes Fes 2 . The equivalent of a compound of two elements is the sum of file equivalents of its components. Thus the equivalent of pro toxide of iron FcO is 350'00 -|- lOO'OO = 450'00, the equivalent of red oxide of iron EoV is 2(350'00) + 3(ioo - oo) = looo'oo. The law of combination of simple substances applies also to their compounds, which unite with each other in quantities proportional to low multiples of their equivalents. The com bination is denoted by the symbols of the compounds having the sign + placed between them, and having the number of multiples of each prefixed. Thus the mineral proustite, consisting of three equivalents e 3