| Example.—Let the weight of the pyknometer be | 15.2985 | grams. |
| and its weight with pure water at 15°.5 be | 26.9327 | ” |
| Then the weight of water is | 11.6342 | ” |
| The weight filled with the sugar solution is | 28.3263 | ” |
| Then the weight of the sugar solution is | 13.0278 | ” |
The specific gravity of the sugar solution is therefore, 13.0278 ÷ 11.6342 = 1.1198.
For strictly accurate results the weight must be corrected for the volume of air displaced, or in other words, be reduced to weights in vacuo. This however is unnecessary for the ordinary operations of agricultural analysis.
If the volume of the pyknometer be desired, it can be calculated from the weight of pure water which it holds, one cubic centimeter of pure water weighing one gram at 4°.
The weights of one cubic centimeter of water at each degree of temperature from 1° to 40°, are given in the following table:
Table Showing Weights of One
Cubic Centimeter of Pure Water
at Temperatures Varying from
1° To 40°.
| Temperature. | Weight, Gram. | Temperature. | Weight, Gram. |
|---|---|---|---|
| 0° | 0.999871 | 21° | 0.998047 |
| 1° | 0.999928 | 22° | 0.997826 |
| 2° | 0.999969 | 23° | 0.997601 |
| 3° | 0.999991 | 24° | 0.997367 |
| 4° | 1.000000 | 25° | 0.997120 |
| 5° | 0.999990 | 26° | 0.996866 |
| 6° | 0.999970 | 27° | 0.996603 |
| 7° | 0.999933 | 28° | 0.998331 |
| 8° | 0.999886 | 29° | 0.995051 |
| 9° | 0.999824 | 30° | 0.995765 |
| 10° | 0.999747 | 31° | 0.995401 |
| 11° | 0.999655 | 32° | 0.995087 |
| 12° | 0.999549 | 33° | 0.994765 |
| 13° | 0.999430 | 34° | 0.994436 |
| 14° | 0.999299 | 35° | 0.994098 |
| 15° | 0.999160 | 36° | 0.993720 |
| 16° | 0.999002 | 37° | 0.993370 |
| 17° | 0.998841 | 38° | 0.993030 |
| 18° | 0.998654 | 39° | 0.992680 |
| 19° | 0.998460 | 40° | 0.992330 |
| 20° | 0.998259 |
From the table and the weight of water found, the volume of the pyknometer is easily calculated.
Example.—Let the weight of water found be 11.72892 grams, and the temperature 20°. Then the volume of the flask is equal to 11.72892 ÷ 0.998259, viz., 11.95 cubic centimeters.
50. Use of Pyknometer at High Temperatures.—It is often found desirable to determine the density of a liquid at temperatures above that of the laboratory, e. g., at the boiling-point of water. This is easily accomplished by following the directions given below: