x = ((100-P)×M×H)/((100×H)-(P×M))
For example, "tailings" (sp. g. 3.0) containing 27.2 per cent. of pyrites (sp. g. 5.1) will contain (100-27.2), 72.8 per cent. of earthy matter having a mean sp. g. of x:
x = ((100-27.2)×3×5.1)/((100×5.1)-(27.2×3))
= 1113.84/428.4 = 2.6
The differences in sp. g. corresponding to differences in strength have been carefully determined and tabulated in the case of the stronger acids and of many other liquids. Such tables are given at the end of this book.
To Calculate the Weight of a Measured Volume of Mineral or Rock.—Multiply the cubic feet by 62.4 and then multiply by the sp. g. of the stuff, the answer gives the weight in pounds. For example, 100 cubic feet of quartz weighs 100×62.4×2.6 = 16,224 lbs. The weight of any mass of mineral of known extent and sp. g. is ascertained in this way.
The following table gives the specific gravities of some of the commoner minerals.
| Barytes | 4.5 |
| Blende | 4.0 |
| Calcite | 2.6 |
| Cassiterite | 6.9 |
| Chalybite | 3.8 |
| Copper pyrites | 4.2 |
| Fluor | 3.1 |
| Galena | 7.5 |
| Hæmatite | 5.0 |
| Mispickel | 6.2 |
| Pyrites | 5.0 |
| Quartz | 2.6 |
FOOTNOTES:
[8] The difference of 20 or 30 milligrams is disregarded here because it detracts equally from the actual weight of the water and liquid to be determined. If the liquid is a heavy one the difference shows itself in the third or second place of decimals. The correction may be made by deducting from the weight of the flask 0.0012 grams for each gram of water it holds.