ATOMIC WEIGHTS

The atomic weight of a mineral is the proportion in which its elements are united, i.e., they represent the weights of the different atoms in the minerals. Hydrogen, being lightest, is made the unit.

Supposing it becomes desirable to find the proportional weights of the elements of any substance with a known chemical formula. Multiply the atomic weight of each element by the number of atoms of such element, and add these products together; this will give the weight of all. The proportion of each is arrived at by a simple calculation.

For instance: How much metallic silver is there in 100 pounds of Argentite, or silver glance, whose composition is Ag2S?

Then Ag equals 108 times 2,--216. S equals 32 times 1,--32. So that in every 248 pounds of the glance there are 216 pounds of metallic silver, and by proportion we find its percentage is 87.1.

The following tables give the symbols, atomic weights and specific gravities of certain abundant elements. Rare elements are omitted: Symbol. At. Wt. Sp. Gr. Aluminum Al 27.5 2.56 Antimony Sb 122.0 6.70 Arsenic As 75 5.70 Barium Ba 137 4.00 Bismuth Bi 210 9.7 Calcium Ca 40 1.58 Carbon C 12 3.50 Chromium Cr 52.5 6.81 Cobalt Co 58.8 7.70 Copper Cu 63.5 8.96 Gold (Aurum) Au 196.77 19.30 Hydrogen H 1.0 0.069 Iodine I 127.0 4.94 Iron (Ferrum) Fe 56.0 7.79 Lead (Plumbum) Pb 207.0 11.44 Manganese Mn 55.0 8.1 Mercury (Hydrargyrum) Hg 200 13.59 Nickel Ni 58.8 8.60 Nitrogen N 14.0 0.972 Oxygen O 16.0 1.105 Phosphorus P 31.0 1.83 Platinum Pt 197.4 21.53 Potassium (Kalium) K 39.0 0.865 Selenium Se 79.5 4.78 Silicon Si 28.0 2.49 Silver (Argentum) Ag 108.0 10.05 Sodium (Natrium) Na 23.0 0.972 Sulphur S 32.0 2.05 Tellurium Te 129.0 6.02 Tin (Stannum) Sn 118.0 7.28 Zinc Zn 65.0 7.14