Common basic instruments and precautions for use in the laboratory

1. Test tube: (1) A reaction container used as a small amount of reagent, used at normal temperature or under heating. (2) Sometimes used to collect a small amount of gas, as a simple generator, or as a gas cylinder.

Note: (1) There is no water droplet on the outer wall before heating, and the maximum liquid is less than 1/3 of the tube volume. (2) It cannot be quenched after heating to prevent cracking.

2. Test tube holder: used to hold the tube for heating.

Note: (!) When using the test tube holder, hold the long handle and apply pressure to the short handle with your thumb to control the tube clamp or release. (2) Do not burn the test tube holder while heating. The tube should be inserted into the tube clamp from the bottom and clamped in the middle and upper part of the tube.

3. Glass rod: (1) Stir the solution to prevent the liquid from splashing due to excessive local temperature, or to accelerate the dissolution or accelerate the reaction rate. (2) Mix the solid or solution evenly. (3) Used as a drainage when dissolved and filtered. (4) Used to extract a small amount of solution to test the properties of the solution.

Note: After work, you must wash off the work bar to prevent contamination of the reagents.

4. Plastic dropper: used to suck and drop a small amount of liquid (dropper bottle for holding liquid medicine)

Note: (1) Do not inhale the liquid into the rubber cap to prevent the liquid from corroding the rubber cap. (2) Wash immediately after use, and then take other medicines. (3) Do not protrude into the container during dripping, and must not come into contact with the reactor. (4) Upright translation when taking liquid. (5) When using a dropper to drip the liquid, the tip of the dropper is near the reactor.

5, alcohol lamp: used as a heat source. The lamp flame is divided into three parts: the flame heart, the inner flame and the outer flame.

Note: (1) The amount of sprinkling does not exceed 2/3 of the volume, not less than 1/3. (2) Matching when igniting, it is strictly forbidden to ignite. (3) It is strictly forbidden to add sprinkling to the burning sprinkler. (4) The outer flame of the lamp used for heating. When the lamp is off, use the lamp cap to extinguish.

6. Beaker: used as a reaction container for formulating solutions and larger amounts of reagents, used at room temperature or under heating.

Matters needing attention: (1) should be placed on the asbestos net when heated to make it evenly heated. (2) There is no water droplet on the outer wall before heating. (3) When preparing the solution, it is preferable that the solution is 1/2 of the volume.

7. Measuring cylinder: measuring the volume of liquid

Note: (1) Do not use a measuring cylinder to prepare a solution or carry out a chemical reaction. (2) Can not be heated, nor can it contain hot solution to avoid bursting. (3) When measuring liquid, it should be at room temperature. (4) When reading, the line of sight should be tangent to the lowest point of the liquid hand. (5) To measure a known volume of liquid, a cylinder that is slightly larger than the known volume should be selected, otherwise the error will be too large. If measuring 15mL of liquid, a measuring cylinder with a capacity of 20mL should be used. A measuring cylinder with a capacity of 50mL or 100mL cannot be used.

8. Gas cylinder: used to collect or store a small amount of gas.

Note: (1) When collecting gas, the frosted glass piece and the bottle mouth should be evenly coated with a layer of Vaseline before use. The frosted glass piece should be pushed and pulled close to the bottle mouth to complete the opening and closing operations. (2) When the gas is set to be used, there are two ways of placing, that is, the gas density is larger than the air, the bottle mouth should be upward, and vice versa. (3) The gas collection bottle cannot be heated. For some experiments, the bottom of the bottle should be covered with a layer of fine sand or a small amount of water to prevent high temperature solids from splashing off the bottom of the bottle to burst the gas cylinder.

9. Pallet balance: Weigh the quality of solid drugs and other substances.

Note: (1) Put the balance flat before weighing, place the travel code on the scale zero, adjust the balance nuts at the left and right ends to balance the balance. (2) The weighing object is placed on the left disk, and the weight is placed on the right disk; when adding the weight, it cannot be taken directly by hand, and the tweezers are used for clamping; the weight is added in the order of the first big and the small, and finally the code is adjusted. (3) Weighing solid drugs can not be placed directly on the tray. The same type of paper of the same size should be identified on the two trays of the balance, and the medicine should be weighed on paper; the deliquescent or corrosive drugs must also be Weigh in the off-duty container. (4) Drugs that cannot be weighed are to be weighed after cooling to room temperature. (5) After the weighing is completed, the weight should be put back from the small to large size, and the travel code should be moved back to the zero position, and the tray should be placed on the same side of the balance.

10. Funnel: used as a filter, or used to add liquid to a small-diameter container.

Note: (1) When the red raft is used, the funnel should be placed on the funnel frame, and the lower end of the handle should be close to the inner wall of the adapter. The filter paper should be close to the inner wall of the funnel. The edge of the filter paper should be about 5 mm below the edge of the funnel. It should be wetted with distilled water before leaving no air bubbles. (2) When pouring the separator, adhere to one side of the three layers of filter paper along the glass rod. The liquid level of the separator is lower than the edge of the filter paper.

11, long neck funnel: for liquid addition, often used to assemble gas generators.

Note: (1) can not be directly heated by fire. (2) When assembling the gas generator, the long neck end of the funnel should extend below the liquid level to prevent gas from escaping.

12. Evaporating dish: used as evaporation, concentrated solution or dry solid.

Note: (1) It is used with a tripod or an iron frame with an iron ring. (2) It can be heated directly. (3) When evaporating, heating is stopped when a large amount of solids appear in the evaporating dish, and the solution is evaporated to dryness with residual heat. (4) The hot evaporating dish should not be placed directly on the test bench, and the asbestos net should be placed on it.

13. Sink: It is used as a container for water storage. It is often used in conjunction with a gas collection bottle to collect gas by drainage.

Note: Can not be heated, nor can it contain hot water with too high temperature.

14. Conical flask: (1) Used to assemble a gas generator. (2) The susceptor of the distillate at the time of distillation. (3) can heat liquid substances (asbestos net on the mat) (4) is often used for titration

Note: (1) should be placed on asbestos net when heating. (2) Do not hold too much liquid to facilitate oscillation.

15. Gas scrubber: An instrument used to remove impurities from gases. The liquid absorbent is required to absorb only the impurity gas, and the purified gas neither reacts with the absorbent nor dissolves in the absorbent.

Note: (1) The appropriate liquid absorbent should be selected according to the nature and requirements of the gas. The absorbent is generally not more than 1/2 of the volume. (2) Check the airtightness before washing. (3) The direction of the purge gas flow is: long (tube) inlet (gas), short (tube) outlet (gas).

16. Scale: Usage (1) The commonly used tool for length measurement is the scale. (2) Before using the scale, pay attention to its zero mark, range and minimum scale value.

(3) How to use the scale correctly:

The ruler should be along the measured length (zero own scale line is aligned with the beginning of the measured length; the ruler should be equal to the side of the test object, not skewed; the scale is close to the test object) 2 The worn zero line should not be used. For the ruler where the pile line is worn, the other scale lines should be used as the starting point for measurement. 3 The line of sight should be perpendicular to the ruler when reading. When making an accurate measurement, estimate the next bit of the smallest scale.

17. Spring balance: 1 Check whether the pointer is aligned with the zero mark before use. If it is not aligned, it should be corrected. Otherwise, the measured value will be too small or too large. 2 Before using it, observe the minimum scale value and range of the filter. The force on the spring balance can't exceed its range, otherwise the spring balance will be damaged: 3 Pull the hook back and forth several times before use to avoid the spring filling the shell; 4 During the measurement, the force applied to the spring balance should be the axis direction of the spring scale Consistently, avoid large errors caused by friction between the spring and the outer casing; 5 Correctly read when measuring with a spring balance.

18. Ammeter: The ammeter is a meter that measures the current intensity.

Ammeter reading: 1 Confirm the range used by the ammeter. 2 Depending on the range used, confirm how large the current value is for each large and small grid on the dial. When using 0-0.6 amp range, each large grid is 0.2 amps, each granule is 0.02 amps, with 0-3 ampere, each large grid is 1 amp, each grid is 0.1 amp. The measured current value is equal to the current value of the large cell plus the number of cells of the small cell multiplied by the current value represented by each cell. The reading should be such that the line of sight is perpendicular to the scale surface.

How to use the ammeter and precautions: The ammeter must be connected in series in the circuit. 2 The “+” and “-” terminals of the ammeter should be connected correctly. Connect the ammeter to the circuit. The current must flow from the “+” terminal to the ammeter and out of the “-” terminal. If it is reversed, the ammeter pointer will be deflected in the reverse direction. The current will not be measured. Break the ammeter pointer. 3 The test current should not exceed the current range. When the test current exceeds the range of the ammeter, not only the current value is not measured, but also the pointer of the ammeter can make up the bend, and may even burn out the ammeter. In the case where the magnitude of the supplemental current cannot be estimated in advance, the size can be estimated by the trial method. 4 It is absolutely not allowed to connect the ammeter directly to the poles of the power supply without passing through the appliance. Otherwise, the ammeter will soon burn out and the power supply will be damaged. This connection is absolutely not allowed.

19. Voltmeter: The voltmeter is a meter that measures voltage.

Voltmeter reading: When the reading voltage indicates the number, first determine which range of the voltmeter is used, then determine the voltage value indicated by each large grid and each small grid on the dial scale, and then correctly read according to the pointer position.

Use of voltmeter:

The voltmeter should be connected in parallel in the circuit. 2 The connection of the voltmeter “+” “-” terminal should be correct. When connecting the voltmeter, the current must flow from "+" into the voltmeter, and the voltmeter from the "-" should be the same as the connection of the ammeter terminal. 3 The measured voltage cannot exceed the range of the voltmeter. If the measured voltage exceeds the range of the voltmeter, not only the voltage value can be measured, but also the pointer of the voltmeter will be bent or even burn out the voltmeter. In the case where the measured voltage cannot be estimated in advance, the test touch method may be used to determine whether the measured voltage exceeds the range;

20. Sliding rheostat: The resistance is changed by changing the length of the resistance wire connected to the circuit.

Use: The sliding rheostat has four terminals. Using a varistor, it is necessary to connect it in the circuit in order to change the power supply strength in the circuit and the voltage across some of the circuits by changing the resistance. There are six possible connections for tying the four terminal varistor into the circuit.

The problems that should be noted when using the sliding varistor can be summarized as:

1 sliding varistor should be connected in series with the control circuit.

2 The two terminals of the sliding varistor connected to the circuit must be “on one shot”.

3 To protect the circuit, the slider should be moved to the position where the resistance in the circuit is maximized before the circuit is turned on.

4 The current through the sliding varistor cannot exceed the maximum current allowed to pass. The electric resistance of the sliding varistor is constant.

The advantage of the sliding varistor is that the resistance of the connected circuit can be continuously changed. The disadvantage is that the resistance of the connected circuit cannot be indicated.

21. Electromagnetic relays are important components in electric bells, telephones, and self-controlled circuit devices. The essence is a switch controlled by an electromagnet, which acts like a switch in the circuit.

1 Electromagnetic relay uses low voltage, weak current to control high voltage, high current working circuit: the composition of the control circuit - electromagnet, low voltage power supply, switch. The working circuit consists of the contact parts of the high voltage power supply, the motor and the electromagnetic relay.

2 Working principle of electromagnetic relay: When the electromagnet is energized, the armature is sucked down to make the moving and static contacts contact, and the working circuit is closed. When the electromagnet is de-energized, it loses its magnetism, and the spring connects the armature and cuts off the working circuit.

3 Application of electromagnetic relay: control high voltage and strong current with low voltage and weak current; realize remote operation and automatic control

22. Convex lens: A glass element whose surface is a part of a spherical surface and whose thickness is thin and has a thin edge is called a convex lens. It is an important component of a camera, a slide projector, a teaching projector, a magnifying glass, and a microscope.

1 main lens of the convex lens, focus, focal length:

Main optical axis: A straight line passing through the center of two spherical spheres.

Focus: A light equal to the main optical axis converges on a point F on the main optical axis.

Focal length: The distance f from the focus to the center of the lens.

2 convex lens has a convergence effect on light.

The camera is made using the principle that when the u>2f, the convex lens is inverted and reduced.

The slide projector is made by the principle that when the convex lens is an upright and enlarged real image when 2f>u>f. The structure of the teaching projector is similar to that of a slide projector, which uses a plane mirror to reflect the image onto the screen.

3 magnifying glass is used as u

The objective lens and the eyepiece of the microscope are convex lenses. The observed object is an enlarged real image outside the focal length of the objective lens within 2 times of the focal length. This enlarged real image is an enlarged virtual image in the focus of the eyepiece, and is enlarged twice to increase the magnification. multiple.

23. A pressure gauge is an instrument that measures the internal pressure of a liquid.

The principle of 1 pressure gauge: the size difference of the liquid level of the two tubes of U-tube reflects the pressure applied on the rubber membrane. When the rubber film on the metal box is pressed, the liquid level on both sides of the U-shaped tube is inferior. The greater the pressure, the greater the difference in height of the liquid surface. 13245

2 pressure gauge can be used to measure the pressure of the gas. The left side of the pressure gauge is connected to the gas to be measured. If the pressure of the gas to be measured is stronger than the atmospheric pressure, the liquid level on the right side of the pressure gauge is higher than the left side; if the pressure of the measured gas is smaller than the atmospheric pressure, the liquid level on the left side is higher than the right side. The side liquid level is high. The pressure difference between the liquid column heights on both sides is equal to the difference between the pressure of the measured gas and the atmospheric pressure.

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