Amy has a master's degree in secondary education and has taught math at a public charter high school.
Did you know that there is a tool that measures how salty saltwater is and how much alcohol your wine has? This little tool is called the hydrometer, which measures the density of a liquid.
Hydrometers look a lot like thermometers, except they don't have an internal liquid that rises and falls. Instead the hydrometer has a weight at the bottom that is calibrated to a specific level. This hydrometer then sinks or rises depending on the density of the liquid. Lighter liquids will make the hydrometer sink and heavier liquids will make the hydrometer rise.
The scales on hydrometers will look backwards to you if you are used to a thermometer scale. A thermometer scale increases as you go up the tube but a hydrometer's scale increases as you go down the tube. This is because heavier liquids make your hydrometer rise thus lowering the location where the top part of the liquid reaches.
Hydrometers have a lot of uses. Some are even calibrated for specific applications.
Want to keep saltwater fish as pets? Or maybe you work in marine biology using saltwater tanks? Hydrometers can be used to measure the density of saltwater. This is important because marine fish require a specific amount of salt in their water. So fish-keepers who mix their own saltwater must use a hydrometer to make sure that their mixture is just right for their fish.
Winemakers use hydrometers to check for the amount of sugars in juices and also to see how much alcohol can potentially be made from a juice.
Milk producers also use hydrometers to check for the density of milk. Pure milk that's not diluted will have a density of 1.03 grams per milliliter at 25 degrees Celsius or a specific gravity of 1.035.
With all these uses, there are also several different scales that hydrometers can have.
The most common and most versatile scale is called the specific gravity scale. This scale has no units since it compares the mass of a liquid to the mass of pure water. Most hydrometers are calibrated to water at 60 degrees Fahrenheit.
When you stick a hydrometer into water at 60 degrees Fahrenheit, it will float at the 1.000 mark. Warmer temperatures will decrease your hydrometer reading and cooler temperatures will increase your reading. For example, when measuring the density of salt water, the hydrometer will read 1.023 at 79 degrees Fahrenheit for a specific gravity of 1.0253 at 60 degrees Fahrenheit.
Another common scale is that used in the wine industry. This scale is called the Brix scale, which measures the amount of sugar in the liquid. The scale goes from 0 to 30, which stands for the percentage of sugar in the liquid. So 13 means the liquid is made up of 13 percent sugar. Wineries use this information to determine whether a certain juice has enough sugar to make wine out of it. This type of hydrometer is also referred to as a saccharometer.
Another scale used in the wine industry is that of potential alcohol. This scale tells you how much alcohol you can make with the amount of sugar still in the liquid. This scale does not tell you how much alcohol is already in your liquid though. To calculate this, you'll need to take a potential alcohol reading before your fermentation and another reading after fermentation. The difference is your alcohol content of your liquid.
For example, if you get a reading of 17 percent before fermentation and 2 percent after fermentation, then your alcohol content is 17 - 2 = 15 percent. Alcohol hydrometers are also referred to as alcoholmeters.
In the milk industry, your hydrometer can be calibrated for measuring grams per milliliter or for the specific gravity scale. Milk has a density of 1.03 grams per milliliter at 25 degrees Celsius and a specific gravity of 1.035. On a milk hydrometer calibrated for grams per milliliter, you'll see markings for 1 and 2 and 1A and 2A. Normal milk will measure at 1 or 2 and low density milk will measure 1A and 2A. A milk hydrometer is also called a lactometer.
Reading a Hydrometer
To read a hydrometer, you need to look at where your water level is.
Your reading should not be at the top of these waves, but where your liquid is when there are no waves. Sometimes, your liquid will stick to the sides of hydrometer. If this is the case, you still don't read the tip of where the liquid touches the hydrometer. You read the level of your liquid when it's undisturbed.
A hydrometer measures the density of a liquid. A weight sits at the bottom, and a scale at the narrow top end. Hydrometers are used in marine fish-keeping, wine-making, and the milk industry. There are different scales depending on the use of the hydrometer.
|Specific Gravity||Calibrated at 1.000 to water at 60 degrees Fahrenheit.|
|Brix||Percentage of sugar in a liquid from 0 to 30.|
|Potential Alcohol||Percentage of potential alcohol that can still be made from the liquid.|
|Milk||Measures either grams per milliliter or specific gravity. Marked with 1 and 2 for normal milk and 1A and 2A for less dense milk.|
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