Discussion: 1. What is the unit of specific gravity? X 2. Why there is a capillary hole through the fitting glass stopper of the pyknometer? 3. Are there any devices to measure the specific gravity of petroleum other than pyknometer or hydrometer? 4. Why there are many shapes for hydrometers? 5. Arrange the following petroleum products according to the increase in API values: Lubrication oil, kerosene, gasoline, gas oil