100 mL pear-shaped glass centrifuge tube with a finely graduated stem, for reading small sediment volumes after spinning.
C1531
C1532
A pear-shaped centrifuge tube exists to measure a very small solid volume accurately. The wide body holds the 100 mL sample; the narrow graduated stem at the bottom is where the sediment collects after spinning. Because the stem is a fraction of the body's diameter, a sediment layer that would be a thin unreadable film in a straight tube becomes a column several millimetres tall against a fine scale.
That is what makes the design standard for sediment and water content in fuels, oils and dairy — anywhere the answer is a fraction of a percent and reading it off a straight-walled tube would be guesswork.
Two stem graduations are available:
| Catalog | Capacity | Graduated stem |
|---|---|---|
| C1531 | 100 mL | 0–1.5 mL |
| C1532 | 100 mL | 0–1 mL |
Choose by the sediment volume expected, not by sample size — both hold 100 mL. The 0–1 mL stem reads a cleaner sample more finely; the 0–1.5 mL stem covers a dirtier one without running off scale, which is the worse failure of the two because the reading is then lost entirely.
Always balance a pear-shaped tube against another of the same type filled to the same level. The mass is concentrated high in the body, and an unbalanced pair is harder on the rotor than a straight tube of the same weight.