What Is an Analytical Balance?

Analytical balance is the most important instrument for accurate weighing in experiments. It can be divided into mechanical and electronic. Mechanical analytical balances can be subdivided into ordinary analytical balances, air-damped balances, semi-automatic photoelectric balances, fully automatic photoelectric balances and single-pallet balances. These balances use the principle of leverage, but differ in structure and use. Mechanical balances can meet the accuracy requirements of general quantitative analysis with a sensitivity of 0.1 mg. The biggest advantage of this type of balance is that the structure is intuitive, but the balance parts are complex, the operation is demanding and time consuming. ^[1]

There are many types of analytical balances: mechanical, electronic, manual, semi-automatic, fully automatic, and so on.

Calibration method of analytical balance: can be divided into

Analytical balance is better than

(1) Direct weighing method: If the solid sample in question is not hygroscopic and stable in air, the direct weighing method can be used. First, accurately weigh the clean container on the balance, then use a medicine spoon to take an appropriate amount of sample into the container, and weigh its total mass. Subtract these two mass values to get the mass of the sample.

(2) Weight reduction method: Weight reduction methods are generally used on analytical balances. First weigh out the exact mass of the sample and the weighing bottle, and then pour a portion of the sample in the weighing bottle into the container of the medicine to be held until the estimated quantity is close to the required quantity. After pouring the medicine, cover the weighing bottle, place it on the balance and weigh it accurately. The difference between the two masses is the mass of the sample. If too much medicine is poured into the container at one time, it must be discarded and never returned to the weighing bottle. If the sample to be poured is not enough, it can be added again, but the frequency should be less.

(3) Designation method: For samples with stable properties, sometimes for the convenience of calculation, we can weigh the specified quality.

1. When the rotary switch is used, it must be opened and closed slowly and evenly. If it is too fast, the blade will be damaged, and the measurement error will be caused by excessive shaking.

2. During each weighing, the balance should be closed. Never increase or decrease the weight when the balance is turned on, or place the weighing object in the weighing pan.

3. Appropriately estimate the weight to be added before weighing, and then turn on the balance. Observe that the pointer shifts backwards, then increase or decrease the weight, and turn on the balance again until the reading on the projection screen is still to within 10mg.

4. When the weighed object is below 10mg, it can be read out directly on the projection screen.

5. The indoor temperature of the balance should be maintained at 20 ± 2 to avoid sunlight and eddy currents or cold and heat on one side. Silica desiccant should be placed in the frame cover. Do not use acidic liquids as desiccants.

6. The weighed object shall be placed in the center of the weighing pan, and shall not exceed the maximum weighing capacity of the balance.

7, too hot and cold and volatile and corrosive objects can not be weighed in the balance.

8. After using the balance, turn the brake off and the weight index to zero, and cover the balance with a sleeve.

9. When the entire balance is to be moved, the beam, left and right weighing pans, ring weights, lifting ears and other parts must be carefully removed and put into the box. Other parts cannot be removed at will. ^[5]

(1) The action should be slow and light: the lifting pivot is slowly opened and opened to the maximum position, and the lap code is slowly turned to prevent the lap code from falling off or out of position.

(2) The weighing object cannot be placed directly in the weighing pan. Depending on the different properties of the weighing object, it can be placed in a piece of paper, a watch glass or a weighing bottle. Do not weigh objects that exceed the maximum load of the balance.

(3) The balance cannot be replaced during the same weighing process to avoid relative errors.

(4) In addition to following the relevant operating rules of the tray balance when using the analytical balance, it should also be noted that the weight of the balance should be supported first when adding weights, picking and weighing samples or other reasons when touching the balance, otherwise the knife edge will be damaged. It is the most important one in using the balance rules. Close the balance door every time you weigh. When turning on the balance after adding weights, the pointer swing should be controlled between 2 and 4 divisions. The weighed sample is weighed in a clean and dry weighing bottle or watch glass depending on its nature. Weighing bottles must not be held by hand. They must be held by filter paper strips. At the end of weighing, check whether the balance beam is properly supported, whether the weights are complete, whether medicines have fallen into the balance, whether the balance door is tightly closed, and whether the cloth cover is well covered. After using the balance for a period of time, it must be sent to the metrology department for verification and adjustment. Comprehensive cleaning of the balance should be carried out twice a year.

1. Maximum weighing: 200g

2.Minimum division value: 0.1mg

3. Mechanical coding range: 10mg ~ 199.99g

4. Optical reading range: 0-10mg

5. Differential scale full value: 10mg

6. Scale value per cell: 0.1mg