In practice, the weight of the bottle filled with water will probably be already known; if not, it must be determined. A certain quantity, say 20 grams, of the powdered substance is then transferred carefully to the bottle. The bottle need not be dry inside, but its neck and outside must be. In making this transference a careful worker will make no loss, and the mode of working saves a little time. But it is better to weigh the dry flask; put into it 10 to 20 grams of the powder, and weigh again. The increase in weight gives accurately the weight of powder in the bottle. About two-thirds fill the bottle with distilled water, and mix with the powder by gentle shaking. Air bubbles will disentangle themselves, and rise to the surface of the water. Wash back anything adhering to the stopper with a jet of water, and fill the bottle almost to overflowing. Allow it to stand for a minute or so; replace the stopper; warm to the required temperature; take off the superfluous moisture; wipe and weigh. As an example, take the following:—
| 1. | Weight | of | bottle | 12.681 | grams |
| 2. | " | " | bottle filled with water | 37.708 | " |
| 3. | " | " | bottle with wolfram | 40.821 | " |
| 4. | " | " | bottle with wolfram and water | 61.199 | " |
Subtract (1) from (3) to get the weight of wolfram taken:
40.821 grams
12.681 "
——————
28.140 "
add the weight of the wolfram to the weight of the bottle filled with water:
28.140 grams
37.708 "
——————
65.848 "
subtract (4) from this to get the weight of water displaced:
65.848 grams
61.199 "
——————
4.649 "
Divide the weight of the wolfram by the weight of the water displaced to get sp. g.: