Names and functions of commonly used instruments in chemical laboratories
Experimental instruments are important tools for conducting chemical experiments. "Workers want to do their best, they must first sharpen their tools", the availability of experimental tools,
Directly affect the success and failure of the experiment. According to different experimental purposes, the corresponding experimental method should be selected, and experiments can only be carried out with different experimental instruments. The structure and performance of the experimental instrument determine its unique operating method and different scope of application. Therefore, we must have a complete understanding of the relevant knowledge and functions of chemical instruments in order to master it, use it correctly, and achieve handy on the basis of proficiency; complete various experiments. Here we introduce the classification of common chemical instruments and the names, performance, specifications and precautions of various instruments.
1. Classification of common instruments
In general, according to the main purpose of the instrument, common chemical experiment instruments can be divided into the following 8 categories:
(1) Measurement
An instrument used to measure mass, volume, temperature, density, etc. Most of these instruments are glass measuring instruments. There are mainly burettes, pipettes, measuring cylinders, measuring cups, etc.
(2) Reaction
The instruments used for chemical reactions also include a part of the instruments that can be heated. Most of these instruments are glass or porcelain burners. There are mainly test tubes, flasks, evaporating dishes, crucibles, etc.
(3) Containers
Reagent bottles for holding or storing solid, liquid, gas and other chemical reagents, etc.
(4) Separation
Apparatus for separation, purification, filtration, liquid separation, extraction, evaporation, burning, crystallization, fractionation, etc. There are mainly funnel, separating funnel, evaporating dish, flask, condenser, crucible, beaker, etc.
(5) Solid clamping
Supplies or instruments for fixing and holding various instruments. There are mainly iron clips, iron rings, iron stand, funnel stand and so on.
(6) Heating
Supplies or instruments used for heating. There are mainly test tubes, beakers, flasks, evaporating dishes, crucibles, etc.
(7) Supporting categories
Glass tubes, glass valves, rubber tubes, rubber plugs and other supplies or instruments used for assembling and connecting instruments.
(8) Other categories
Inconvenience belongs to other instruments or supplies of the above types.
2. Name and use of common instruments in middle school chemistry
(1) Measuring instruments
1. Measuring Cup
The measuring cup is a measuring type (symbol Ex) measuring device, which is used to measure the volume of liquid discharged from the measuring device. The volume of the discharged liquid is the volume read from the scale value when the liquid is in the measuring instrument.
There are 2 types of measuring cups. When facing the indexing table, the measuring cup pouring nozzle is to the right, which is convenient for left-handed operation, and is called the left-handed measuring cup. When the pouring nozzle is to the left, it is called a right-handed measuring cup. Measuring cups up to 250 mL are left-handed, those above 500 mL are right-handed.
6. Thermometer
Thermometer is an instrument used to measure temperature. There are many types of digital thermometers, thermal thermometers and hemorrhoids. The temperature of the glass liquid is commonly used in the laboratory. Thermometers can be divided into standard thermometers and practical thermometers according to usage and measurement accuracy. The standard temperature juice has high accuracy, and it is mainly used to calibrate other thermometers. Practical thermometer refers to the thermometer used for actual temperature measurement, mainly including experimental thermometer, industrial thermometer, meteorological thermometer, medical thermometer and so on. The stick industrial temperature juice is commonly used in middle schools. Among them, the range of the alcohol thermometer is 100 ℃, and the mercury thermometer uses two range specifications of 200 ℃ and 360 ℃.
Precautions for use
(1) A thermometer suitable for the measurement range should be selected. It is strictly forbidden to use the thermometer beyond the range.
(2) When measuring the temperature of the liquid, the liquid bubble of the thermometer should be completely immersed in the liquid, but must not touch the wall of the container. When measuring the temperature of the steam, the liquid bubble should be above the liquid level. When measuring the temperature of the distillation fraction, the liquid bubble should be slightly lower than the branch pipe of the distillation flask.
(3) When reading, the line of sight should be level with the highest point (mercury thermometer) or the lowest point (alcohol thermometer) of the liquid column meniscus.
(4) It is forbidden to use temperature juice instead of glass rod for stirring. After use, wipe it clean, put it in a paper sleeve, and store it away from heat sources.
7. Pallet balance
Tray balance is an instrument used to roughly weigh the mass of materials. Each balance is equipped with a box of code. There are two kinds of common load in the middle school laboratory: 100 g (01 g) and 200 g (02 g). The load is also called the load capacity, which refers to the maximum weight that can be weighed. Sensitivity refers to the balance error (±), for example, a tray balance with a sense of 01 g means that the error is ± 01 g
, So it cannot be used to weigh items with a mass less than 01 g.
Precautions for use
(1) Before weighing, the balance should be placed steadily, and the cursor should be moved to the zero position of the scale to check whether the swing of the balance is balanced. If the balance is reached, the number of grids on the left and right sides of the scale indicated by the pointer when swinging is nearly equal. When the pointer is stationary, it should be pointed at the center of the scale. If the swing of the balance is not balanced, you can adjust the left and right screws to balance the swing.
(2) Weighing objects can not be placed directly on the tray, you should put a piece of paper of the same size on the two trays, and then put the reagent to be weighed on the paper to weigh. Wet or corrosive reagents must be weighed in glass containers (such as watch glass, beakers or weighing bottles).
(3) Put the weighing object on the left plate and the weight on the right plate. The weights should be picked with tweezers. First add the mass code of the mass, then add the weight of the small mass, and finally move the moving code until the pointer swings to a balance.
(4) After weighing, the weights should be put back into the weight box in order. Move the run code back to zero.
(2) Reaction instruments
1. Test tube
The test tube is used as a reaction container for a small amount of reagents, and can also be used to collect a small amount of gas. Test tubes are usually divided into flat-mouthed test tubes, inverted test tubes, and test tubes with supports according to their uses. The flat-mouth test tube is suitable for general chemical reactions, and the reversing test tube is suitable for adding a rubber stopper. The test tube with a support can be used as a gas generator, as a gas scrubber or a small amount of distillation. The size of the test tube is generally specified by the product of the outer diameter of the tube and the length of the tube, which is usually 10 × 100 mm, 12 × 100 mm, 15 × 150 mm, 18 × 180 mm, 20 × 200 mm and 32 × 200 mm.
Precautions for use
(1) When using test tubes, test tubes of appropriate size should be selected according to different dosages. Use the test tube with your bare hands to hold the upper edge of the test tube with the three fingers of your finger, food, and middle finger. When oscillating, keep your wrist and arm still.
(2) The liquid heating should not exceed the volume, and it should be at a 45 "angle with the desktop, and the nozzle should not face yourself or others. If you want to keep it boiling, you can heat the liquid surface.
(3) For powdered reagents, use a paper trough to feed the bottom of the tube. When holding granular solids, tilt the test tube so that the particulates slide slowly into the bottom of the tube along the test tube wall.
(4) The test tube should be clamped away from the mouth of the tube. When heating, the outside of the test tube should be wiped dry, and the test tube cannot be heated by hand. After heating, care should be taken to avoid sudden cooling to prevent bursting.
(5) When heating the solid reagent, the bottom of the tube should be slightly higher than the mouth of the tube. When finished, it should continue to be fixed or placed on the asbestos mesh to allow it to cool naturally.
2. Beaker
The beaker is usually used as a reaction vessel when the amount of reactants is large. It is also used to prepare solutions, accelerate the dissolution of substances, and promote the evaporation of solvents. There are many types and specifications of beakers, and low-level beakers are commonly used in middle schools. In order to facilitate the addition of a certain amount of liquid when in use, white volume marks are printed on the outer wall of some beakers. This beaker is called a printed beaker, and some is called a scale beaker. The index is not very accurate, and the allowable error is generally ± 5%, so the word "APPROX" is printed on the index table, which means "approximate volume", so it cannot be used as a measuring instrument. The specifications of the beaker are distinguished by the size of the volume, commonly used is 50 mL, 100 mL
, 250 mL, 500 mL, etc.
Precautions for use
(1) The solution contained in the beaker should not be too much, about the volume, but when heated, the solution should not exceed the volume.
(2) The beaker cannot be burnt dry. It can be heated for a long time when it is filled with liquid, but it must be cushioned with asbestos mesh.
(3) When holding the beaker, take the outer wall and keep your fingers away from the inner wall. Use the beaker clamp to hold the heated beaker.
(4) When it is necessary to stir the solution contained in the beaker with a glass rod, the glass rod should be evenly rotated along the wall of the cup, and do not hit the wall and bottom of the cup.
(5) The beaker should not be used for long-term storage of chemical reagents. After use, it should be washed, dried, and stored upside down.
3. Flask
The flask is used as a container with many reactants and takes a long time to heat, with liquid to participate in the reaction. The bottleneck has a small diameter, and it is often used to generate steam or be used as a gas generator after being equipped with a plug and required accessories. Flasks have a wide range of uses, so there are many types. There are two types of round bottom flasks and flat bottom flasks commonly used in middle schools. Round bottom flasks are generally used as reaction vessels under heating conditions. Flat-bottom flasks are used for gas generators without heating, and are also commonly used to assemble wash bottles. Because the bottom of the flat-bottom flask is small and the edges are ribbed, the stress is large and it is easy to burst when heated. Therefore, it is generally not used in reaction vessels under heating conditions. The specifications of the flask are distinguished by the size of the volume, commonly used are 150 mL, 250 mL and 500 mL.
Precautions for use
(1) The thickness of the bottom of the round bottom flask is relatively uniform, and there are no edges. It can be used for a long time with strong heat.
(2) When heating, the flask should be placed on the asbestos mesh, and it cannot be directly heated by flame.
(3) After the experiment is completed, the heat source should be removed, and after still cooling, the waste liquid should be treated and washed.
4. Distillation flask
Distillation flasks belong to the category of flasks. The difference is that there is a slightly downward branch at the neck of the bottleneck, which is dedicated to the distillation liquid container. There are two types of distillation flasks, reduced pressure and normal pressure. Atmospheric pressure steamed burr flask also has three types of branched tubes on the neck, middle and bottom,
For the distillation of liquids with a higher boiling point, use a distillation flask with a branch pipe at the bottom of the neck, and use a distillation flask with a branch pipe above the lower boiling point. While the branch pipe is located in the bottleneck, it is often used to distill the liquid of general boiling point. The specifications of distillation flasks differ by volume, and they are usually 150 mL and 250 mL.
Make considerations
(1) When configuring accessories (such as thermometer, etc.), appropriate rubber plugs should be selected, and special attention should be paid to check whether the air tightness is good.
(2) When heating, it should be placed on the asbestos mesh to make it evenly heated.
5. Erlenmeyer flask
Erlenmeyer flask is also called Erlenmeyer flask or Erlenmeyer flask. The head of the Erlenmeyer flask has a large bottom and a small mouth. After the solution is filled, the center of gravity is lowered, which is very convenient for hand-held oscillation, so it is often used as a titration container in volume analysis. It is also commonly used in laboratories to assemble gas generators or wash bottles.
The size of the Erlenmeyer flask is distinguished by its volume, commonly used are 150m1, 250ml and so on.
Precautions for use
(1) When oscillating, use your right thumb, index finger, and middle finger to hold the bottleneck, use your ring finger to gently support the lower part of the bottleneck, relax your wrist, and use your palm to force your fingers to make a circular vibration.
(2) When the conical flask needs shaking, the solution contained in the flask does not exceed the volume. If it is necessary to heat the liquid contained in the Erlenmeyer flask, it must be lined with asbestos mesh.
6. Qu neck Zhen Qu neck bottle is also called Qu neck bottle or Qu neck Zhen. It is a long-term, practical and simple instrument. In addition to the only one with a ground glass stopper, the container is connected to the neck. The lines are smooth and in one go. It is used as a reaction vessel or distiller.
The biggest advantage of the curved flask is its simple structure. It can be connected to the glass container through the receiver, or directly to the inclined flask, without the need for a rubber stopper or rubber tube, so it is resistant to corrosion. For example: when making nitric acid in the laboratory, you can put solid sodium nitrate from the stopper first, then add appropriate concentrated sulfuric acid, stopper the bottle stopper, and heat it slightly. liquid. No leakage accidents caused by nitric acid corrosion and aging due to rubber products at the connection. The size of curved neck face differs by volume, commonly used are 125 mL, 250 mL and 500 mL.
Precautions for use
(1) If it needs to be fixed on the iron stand, the bottle stopper should be on the top, and the iron clip should hold the curved neck near the container, so that the curved neck naturally forms an angle with the desktop.
(2) Asbestos net must be put on when heating.
(3) After the experiment, it must be fixed and allowed to stand. After it is cooled, the residue is poured out from the neck of the curved neck, and then water is added from the mouth of the bottle stopper, repeatedly washed, washed, and placed.
7. Kaipu generator
The Qipu generator is often called a gas generator. It was named after the invention by the Dutch chemist Qipu in 1862. It is used as a generating device that produces no-soluble gas from the reaction of massive solids and liquids without heating.
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