What are the weighing methods for analytical balances?

What are the weighing methods for analytical balances?

Analytical balances are no longer unfamiliar. It is an indispensable weighing instrument for quantitative analysis. The analytical balance is a more accurate weighing instrument than the platform scale, and can be accurately weighed to 0.0001g (ie 0.1mg) or more. There are also many types, including mechanical analytical balances, electronic analytical balances, manual analytical balances, and semi-automatic analysis of equals. So, do you know the weighing method of the balance? Let's talk briefly about the weighing method of the analytical balance. At present, there are three methods for weighing the balance, namely: direct weighing method, reduction method and designation method.

Direct weighing method:

The so-called solid sample can be directly weighed if it is not hygroscopic and stable in air. First accurately weigh the quality of the clean container on the balance, then use a spoon to take a proper amount of the sample into the container and weigh its total mass. The values ​​of the two masses are subtracted to give the mass of the sample.

Reduction method:

The weighing method is generally used for weighing on an analytical balance. The exact mass of the sample and the weighing bottle is first weighed, and then the sample in the weighing bottle is poured into a container of the drug to be held, and the estimated amount is close to the amount obtained. After analyzing the balance , put the weighing bottle on the balance and place it on the balance to accurately weigh its quality. The difference between the two masses is the mass of the sample. If too many medicines are poured into the container at one time, the weight must be discarded and never returned to the weighing bottle. If the sample to be poured is not enough, it can be added once more, but the number is less.

Designation method:

For samples with relatively stable properties, sometimes for the calculation of the sample, the sample of the specified quality can be weighed. When weighing by the specified method, place a watch glass on each side of the balance plate (their mass is as close as possible), adjust the balance point of the balance to the center scale, and then add a fixed mass weight to the left balance pan. Add the sample to the right balance pan (this is convenient to pick and place the sample) until the equilibrium point of the balance reaches the original value. At this time, the mass of the sample is the specified mass.

The above is the weighing method of the analytical balance . You can make a preliminary understanding. In addition, when using the analytical balance for the first time, you should check whether the analytical balance is in a horizontal position, whether the power supply voltage is matched, and the weighing bottle should be removed in time. Paper), close the side door and cut off the power. Usually pay more attention to detail, and the service life of the analytical balance is also extended.