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An analytical balance is any balance that uses comparisons to make measurements of weight. Analytical means to compare, and until the 1940’s a common two-pan balance was used to compare measurements of a known weight to an unknown weight. Comparing weights is still used in modern one-pan analytical balances, which are commonly used to measure small, precise weights. Most are required to measure weights to an accuracy of 0.0000035 ounces (0.1 mg).
Chemistry requires the most use of analytical balances because very small amounts of chemicals for certain experiments are often needed. The precision of the measurements comes from a transparent shield that surrounds the pan. Plus all parts are encased to prevent any interference. The balance still needs to be compared to another weight to stay accurate.
By placing a known weight on the analytical balance and using the calibration knobs, it is possible to accurately compare the measurement and adjust it to the known measurement. A tare container is used by opening the shield, placing the tare container on the scale and setting the balance to zero. It becomes easy to use because the tare container’s weight is canceled out. It is important not to bump or contaminate the balance to make sure it stays accurate. Common activities like loud talking and leaning on the work bench can also cause errors in the measurements.
Many electronic analytical balances have safety warnings, like green lights, to help prevent errors. Using a brush after every weighing is common practice as well as using only special cloth to touch any part of the analytical balance. The electronic analytical balance should be called a scale. This is because the final weight is calculated by the small spring force on the scale and not by subtracting masses as a balance does.
The triple beam balance is an example of proper analytical balancing with comparison. The rider arms are used to change the weight against the unknown weight in small interval, producing a great amount of accuracy. The equal arm balance was a common analytical balance that also used glass to enclose the objects being measure.
Inventor Joseph Black changed the world when he began to use a small seesaw device in his balances during the mid-18th century. Two-pan analytical balances were used until the late 1940s. Since then, springs and rider arms could produce as much accuracy in a small single pan balance.