CHEMISTRY. 



grain of hydrogen set free we find that 32-5 grains 

 of zinc are dissolved, and that, therefore, the equiv- 

 alent of zinc is 32-5. Again, when sulphate of 

 copper acts on metallic zinc, for every 32-5 grains 

 of zinc dissolved we find that 31-75 grains of 

 copper are separated therefore, the equivalent of 

 copper is 3175. Once more, when nitrate of 

 silver acts on metallic copper, for every 3175 

 grains of copper dissolved we find that 108 grains 

 of silver are separated , therefore, 108 is the 

 equivalent of silver. Now, one grain of hydrogen 

 unites with 8 grains of oxygen to form 9 grains 

 of water; 32-5 grains of zinc unite with 8 grains 

 of oxygen to form 40-5 grains of oxide of zinc ; 

 3175 grains of copper and 108 grains of silver 

 unite each with 8 grains of oxygen to form respec- 

 tively 3975 grains of black oxide of copper and 

 1 16 grains of oxide of silver; therefore, the 

 equivalent of oxygen is 8. In the same way, I 

 grain of hydrogen, 32-5 grains of zinc, 3175 grains 

 of copper, and 108 grains of silver unite with 35-5 

 grains of chlorine to form respectively hydro- 

 chloric acid (hydric chloride), chloride of zinc 

 (zincic chloride), chloride of copper (cupric chlo- 

 ride), and chloride of silver (argentic chloride) ; 

 therefore, the equivalent of chlorine is 35 -5. 



In a similar way, the equivalent of any element 

 or radical may be determined, it being always 

 recollected that an element or radical has as 

 many different equivalents as it forms series of 

 compounds. Now, if we compare the different 

 equivalents of the same element or radical, we find 

 that they have a simple arithmetical relation to 

 one another. Thus (taking the equivalent of 

 hydrogen as i), the equivalent of mercury in the 

 red oxide of mercury and in its salts is loo ; in the 

 black oxide of mercury and in its salts, 200 that 

 is, twice loo : the equivalent of copper in the 

 black oxide of copper and in its salts is 3175 ; in 

 the red oxide of copper and in its salts, 63-5 that 

 is, twice 3575 : the equivalent of iron in the 

 ferrous salts is 28; in the ferric salts, 18-6 that is, 

 two-thirds of 28. 



These two facts ist, that the equivalent of an 

 element remains the same through a series of 

 compounds ; and 2d, that the different equivalents 

 of the same element have a simple arithmetical 

 relation to each other enable us to form a system 

 of chemical notation by means of which the com- 

 position of compounds may be fully and distinctly 

 expressed. 



In this system of notation, which is known as 

 the ATOMIC NOTATION, certain symbols are used, 

 each of which represents a definite quantity of a 

 particular element. The subjoined table contains 

 the names of the elements with the symbol of 

 each, and the quantity of the element which the 

 symbol represents. This quantity is called the 

 ' atomic weight ' of the element, for reasons which 

 will be afterwards stated. 



TABLE OF ELEMENTS WITH THEIR SYMBOLS AND 

 ATOMIC WEIGHTS. 



Aluminium Al 27-5 



Antimony or Stibium Sb 122 



Arsenicum As 75 



Barium Ba 137 



Beryllium or Glucinum G 9.3 



Bismuth Bi 210 



Boron B II 



Bromine Br 80 



133 

 40- 

 12 

 92 



35 $ 

 52 

 59 



63-5- 

 96 



Cadmium Cd. 



Caesium Cs 



Calcium .-. Ca 



Carbon C 



Cerium Ce.......... ........ 



Chlorine Cl 



Chromium Cr 



Cobalt .Co................!! 



Copper (Cuprum} Cu 



Didymium Di ... 



Erbium Er ... 



Fluorine F 19 



Gallium Ga 68 



Gold (Aurum) Au 196 



Hydrogen H i 



Indium In 113 



Iodine 1 127 



Iridium Ir 197 



Iron (Ferrum) Fe 56- 



Lanthanum La, 92- 



Lead (Plumbum) Pb 207 



Lithium Li f 



Magnesium Mg 24 



Manganese Mn 55 



Mercury (Hydrargyrum) ....tig 200* 



Molybdenum Mo 96 



Nickel Ni 59 



Niobium Nb 97'5> 



Nitrogen N 14 



Osmium Os 199 



Oxygen. O 16 



Palladium Pd 106.5, 



Phosphorus P 31 



Platinum Pt 197 



Potassium or Kalium K 39 



Rhodium Ro 



Rubidium Rb 



Ruthenium. Ru 104-2 



Selenium Se 79-5, 



Silicon Si 28 



Silver (Argentuni) Ag 108 



Sodium or Natrium Na 23 



Strontium Sr 87-5. 



Sulphur S ..... 32 



Tantalum Ta 138 



Tellurium Te 129 



Thallium Tl 204 



Thorium Th 119 



Tin (Stannum) Sn 118 



Titanium Ti 50 



Tungsten or Wolfram W 184 



Uranium U 120 



Vanadium V S 1 ** 



Yttrium Y 61-5 



Zinc Zn 65 



Zirconium Zr 89-5 



If we compare the atomic -weights as given irt 

 this table with the equivalents of the elements,, 

 we shall find that, even in the cases where each, 

 element has only one equivalent, that number has 

 not always been chosen as the atomic weight of 

 the element. Thus, the equivalent is the same as 

 the atomic weight in the case of hydrogen, of 

 potassium, of sodium, of rubidium, of caesium, 

 and of lithium. But the atomic weight is twice 

 the equivalent in the case of barium, of beryllium,, 

 of cadmium, of calcium, of magnesium, of oxygen,, 

 of strontium, and of zinc. Aluminium has only 

 one equivalent, and the atomic weight of alumin- 

 ium is three times its equivalent. Where an element 

 has more than one equivalent, the atomic weight 

 is sometimes equal to one of these equivalents, 

 and sometimes not. Thus, the atomic weight of 

 copper is equal to the equivalent of copper in the- 

 cuprous compounds (red oxide of copper and its. 



104-3. 



