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How to Determine Approximate Specific Gravities of Alloys

1.           Find the reciprocal of the specific gravity of each metal in the alloy. This is done by dividing 1 by the specific gravity. For example, the specific gravity of silver is 10.49 and the reciprocal is 1 divided by 10.49 or .094966.

2.           Multiply each reciprocal by the number of parts per thousand of that metal to be used.

3.           Add the results of the multiplications together.

4.           Divide 1,000 by this total‑the answer is the specific gravity of the alloy.

Example

Find the specific gravity of 14K yellow gold having

583 parts gold, 104 parts silver and 313 parts copper.

First figure the reciprocals of the specific gravities.

Fine Gold ‑ 1 divided by 19.32=.051759

Fine Silver ‑ 1 divided by 10.49=.094966

Fine Copper ‑ 1 divided by 8.96=.111617

Then multiply­

Fine Gold    ‑583 parts by weight X.051759=30.182

Fine Silver   ‑104 parts by weight X .094966= 9.876

Fine Copper ‑313 parts by weight X.111617=34.956

Totals          1000                                        75.014

1000 divided by 75.014=13.33, the specific gravity of the alloy.

*The specific gravity for any one karat will naturally vary for each composition.

## Reducing the formulas down to simple functions to find the percentages of tin and antimony in 2-metal alloys.

To simplify matters a little more, reduce the equations for determing the percentages of tin or antimony in an alloy with a known specific gravity down to these two functions.

TIN - Let TSG = the specific gravity of a tin/lead alloy

or

ANTIMONY - Let ASG = the specific gravity of an antimony/lead alloy

Then:

2076.803 / TSG - 183.059 = the percentage of tin in the alloy

or

1636.416 / ASG - 144.241 = the percentage of antimony in the alloy

TABLE 4

## Specific Gravity, Melting Point, and Weight of Various Metals and Alloys

 Melting Point Weight Specific in Tr. Ozs. Metal °F °C Gravity per Cu. In. Aluminum 1220 660 2.70 1.423 Antimony 1167 630 6.62 3.488 Beryllium 2340 1282 1.82 .959 Bismuth 520 271 9.80 5.163 Cadmium 610 321 8.65 4.557 Carbon - - 2.22 1.170 Chromium 3430 1888 7.19 3.788 Cobalt 2723 1495 8.90 8.90 Copper 1981 1083 8.96 4.719 Gold 1945 1063 19.32 10.180 18 K green 1810 988 15.90 8.375 18 K yellow 1700 927 15.58 8.211 18 K white 1730 943 14.64 7.712 18 K red 1655 902 15.18 7.998 14 K green 1765 963 14.20 7.482 14 K yellow 1615 879 13.07 6.885 14 K white 1825 996 12.61 6.642 14 K red 1715 935 13.26 6.986 10 K green 1580 860 11.03 5.810 10 K yellow 1665 907 11.57 6.096 10 K white 1975 1079 11.07 5.832 10 K red 1760 960- 11.59 6.106 Iridium 4449 2454 22.50 11.849 Iron (pure) 2802 1539 7.87 4.145 Lead 621 328 11.34 5.973 Magnesium 1202 650 1.74 .917 Manganese 2273 1245 7.43 3.914 Molybdenum 4760 2625 10.20 5.347 Nickel 2651 1455 8.90 4.691 Osmium 4892 2700 22.50 11.854 Palladium 2831 1555 12.00 6.322 Phosphorus 111 44 1.82 .959 Platinum 3224 1773 21.45 11.301 15% Iridio Plat. 3310 1821 21.59 11.373 10% Iridio Plat. 3250 1788 21.54 11.349 5% Iridio Plat. 3235 1779 21.50 11.325 Rhodium 3571 1967 12.44 6.553 Ruthenium 4500 2500 12.20 6.428 Silicon 2605 1430 2.33 1.247 Silver 1761 961 10.49 5.525 Sterling 1640 893 10.36 5.457 Coin 1615 879 10.31 5.430 Tin 450 232 7.30 3.846 Zinc 787 419 7.13 3.758