Final answer:
A graduated cylinder is used to perform the API gravity test, where the hydrometer floats to measure the liquid's specific gravity directly.
Step-by-step explanation:
The type of cylinder used to perform the American Petroleum Institute (API) gravity test is a graduated cylinder. In chemistry labs, a graduated cylinder is commonly employed to measure volumes of liquids with varying degrees of precision. When conducting an API gravity test, a hydrometer is used alongside a graduated cylinder. The hydrometer, which has a bulbous bottom and a graduated stem, floats in the liquid contained within the cylinder. The API gravity value is read directly from the hydrometer, which gauges the liquid's density relative to water.
Graduated cylinders come in many sizes and are essential in conducting various laboratory procedures, such as density and specific gravity measurements that are needed for the API gravity test. The fluid's buoyancy will cause the hydrometer to float at a level that correlates with the specific gravity, properly scaled for the API system.