The shape and material of the container is irrelevant as long as there is enough liquid present for the hydrometer to float properly.
A common hydrometer calibration is 60 °F (16 °C). You can use a thermometer to check the temperature of your liquid, and then heat or cool as needed.
The reading on the hydrometer is usually a decimal, but it is derived as a ratio of the density of your liquid to the density of water at a given temperature. In other words, if your hydrometer reads 1. 1, that means your liquid was 1. 1 times as dense as water at that temperature. Note that specific gravity is a unitless measurement. You can look up the specific gravity of some common liquids. Examples are listed below: Acetic Acid: 1. 052 Acetone: 0. 787 Beer: 1. 01 Bromine: 3. 12 Milk: 1. 035 Mercury: 13. 633
For example, if your container weighed 1. 50 pounds with liquid in it and 1. 00 pound empty, your equation would look like this: “1. 50 lb - 1. 00 lb = 0. 50 lb. " Your liquid weighs 0. 50 pounds. Make sure the temperature of your liquid is noted when this weight is taken. You must compare it to water of the same temperature.
Use the same formula to find the weight of the water. If the liquid-filled container weighted 1. 75 pounds, the equation would look like this: “1. 75 lb - 1. 00 lb = 0. 75 lb. " In this example, the water weighs 0. 75 pounds. Make sure that the water is at the exact same temperature as the liquid in question. Otherwise, results may not be accurate.
For example, if you weighed 100 mL of acetone at 25 degrees Celsius, it would weigh 0. 17314 pounds. Weighing the same volume of water at the same temperature would give you 0. 22 pounds. To find the specific gravity of this acetone, you would solve 0. 17314lbs/0. 22lbs=0. 787{\displaystyle 0. 17314lbs/0. 22lbs=0. 787}. This is the specific gravity of acetone.
For example, if you had a sample that was 8 grams and 9 milliliters, your equation would be: “8. 00 g / 9. 00 mL = 0. 89 g/mL. " Weigh an empty container first and record its weight. Next, fill your container with the desired liquid and weigh it again. The mass of your liquid is equal to the second measurement minus the first. For instance, if the filled container weighed 2. 00 lbs and the empty container weighed 0. 75 lbs, the equation would be: “2. 00 - 0. 75 = 1. 25” and the liquid would weigh 1. 25 lbs.
It’s important to find the density of water that is the same temperature as the liquid in order to get accurate measurements.
If you want to get accurate specific gravity calculations, it is necessary that the liquid you are measuring and the water that you are using as a comparison are both at the same temperature.
For example, if you were to take the density of acetone (0. 787 g/mL @ 25 degrees C) and divide it by the density of water (1. 00 g/mL @ 25 degrees C), you would get 0. 787g/mL/1. 00g/mL=0. 787{\displaystyle 0. 787g/mL/1. 00g/mL=0. 787}.
