The balance is a measuring instrument used to determine the weight of objects and substances . In its most general form, it is made up of a vertical column, which carries a perpendicular axis and two saucers that hang from this axis. It has the appearance of a cross from whose arms the two saucers hang and which has one foot to support it.Its operation, as its name implies, consists of the balancing of the forces that are placed on the saucers. In one of them the unknown weight is put; for example, that of an apple. On the opposite pan is put a known weight, which can be taken as a set of standardized weights of 100g, 50g, 25g, etc.In the case of the apple, while the weights are being placed on the opposite plate, it will rise until its height is equal. When the two saucers are at the same height , the forces will be balanced. The weight of the apple will be equal to that of the weights that are put on the opposite plate. By counting the accumulated weight of the weights, we know that of the apple.

What is the scale for?

The balance has been used since time immemorial, when mankind began to develop trade . Sellers of fruits, vegetables, minerals, and gemstones would put these on a scale to see how much was being delivered to customers at a sale. This has been a way to better control the commercial exchange .

Among many other functions, the balance serves to:

  • Weigh fruits and vegetables
  • Weigh minerals
  • Weigh liquids
  • Weigh chemical reagents
  • Weigh loads in vehicles
  • Weigh the human body

Weigh fruits and vegetables

The scale is used to measure the weight of fruits and vegetables, to know how much a seller is going to charge a customer. The merchandise is placed on one of the pans and this weight is counteracted with standardized weights. Since the price of a kilogram of apple is not the same as that of a kilogram of lettuce, they are placed individually, without stirring products.

Weigh minerals

In the field of mining, it is necessary to know the weight of the extracted ores, to calculate stoichiometrically how much of the metal that constitutes them will be able to be extracted, as a result of a chemical process. The same principle of the balance is used, but on a much larger scale. There are already digital scales capable of measuring huge weights, up to two decimal places.

Weigh liquids

The balance is used to weigh liquids as well, not just solids. The difference in this function is that first the weight of the container will be known , which will contain the liquid. Already known, we are going to pour the liquid and measure the final weight. From the weight of the full container we subtract the weight of the empty container. That is the weight of the liquid.

Weigh chemical reagents

In chemical laboratories one of the most frequent tasks is the measurement of quantities of reagents. After calculations of stoichiometry (quantities in which the chemical reagents must be), the grams of the substances are measured on a balance, to begin preparing them as aqueous solutions, for example.

There are the so-called “ analytical balances ”, which are very precise electronic equipment that allows us to measure quantities of chemical substances (except sodium hydroxide NaOH) to four decimal places. They are for very small weights and consist of a house whose doors can be closed, and that isolates the pan. It is on this that the watch glass that will carry the substance is placed.

Also available are the so-called “ granatary balances ”, electronic equipment that is used to measure larger weights than in analytical balances, and in which sodium hydroxide can be weighed. It consists only of a cymbal and its digital display. First of all, the watch glass is placed. The balance is “tared” (or reset to zero) and the reagent is placed on the glass.

Weigh loads in vehicles

For the transport of loads that involve tons, there are industrial scales, which can measure the amount of kilograms (or tons, as required) that a truck carries on its trailer. The weight of the empty truck is taken into account. With the truck on the scale, the individual weight of the load is calculated.

Weigh the human body

During a medical checkup, clinical scales , also known as scales , are used . These are responsible for measuring the weight of the human body. It consists of a platform that will serve as a saucer and on which the patient will stand upright. To determine the weight, a horizontal bar supports a weight, which will exert a kind of torsion on it.

When the patient stands on the platform, the horizontal bar is tilted upwards, indicating that it has been defeated and that this weight must be counteracted. The weight is moved towards the end of the bar, just enough so that the torque is pushing it down. The scale has an arrow indicator that indicates the midpoint, where the patient’s weight and the torque force have balanced. At that midpoint, it is the exact weight of the patient.

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  • Samantha Robson
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    Dr. Samantha Robson ( CRN: 0510146-5) is a nutritionist and website content reviewer related to her area of ​​expertise. With a postgraduate degree in Nutrition from The University of Arizona, she is a specialist in Sports Nutrition from Oxford University and is also a member of the International Society of Sports Nutrition.