Classification and analysis of common experimental

2022-08-14
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Classification and analysis of common experimental consumables in chemical experiments

I. classification of common instruments

generally, according to the different main uses of instruments, common chemical experimental instruments can be divided into the following eight categories:

(I) metrology

instruments used to measure mass, volume, temperature, density, etc. Most of these instruments are glass gauges. It mainly includes burette, pipette, measuring cylinder, measuring cup, etc

(II) reaction type

instruments used for chemical reactions, including some heated instruments. Most of these instruments are glass or porcelain burners. It mainly includes test tubes, flasks, evaporating dishes, crucibles, etc

(III) containers

reagent bottles used to contain or store solid, liquid, gas and other chemical reagents

(IV) separation

instruments used for filtration, liquid separation, extraction, evaporation, burning, crystallization, fractionation and other separation and purification operations. It mainly includes funnel, separating funnel, evaporating dish, flask, condenser, crucible, beaker, etc

(V) solid clamping

articles or instruments used to fix and clamp various instruments. There are mainly iron clips, iron rings, iron frames, funnel frames, etc

(VI) heating supplies or instruments used for heating. It mainly includes test tubes, beakers, flasks, evaporating dishes, crucibles, etc

(VII) supporting class

glass tubes, glass valves, rubber tubes, rubber plugs and other supplies or instruments used in the assembly and connection of instruments

(VIII) other categories

other instruments or supplies that are inconvenient to belong to the above categories

II. Name and use of common chemical instruments in middle school

(I) measuring instruments

1. Measuring cup

measuring cup is a measuring (symbol Ex) gauge, which is used to measure the volume of liquid discharged from the gauge. The volume of discharged liquid is the volume read from the scale value when the liquid is in the gauge

there are two types of measuring cups. When facing the dividing table, the liquid pouring nozzle of the measuring cup is to the right, which is convenient for left-hand operation. It is called left-hand measuring cup. If the liquid pouring nozzle is to the left, it is called a right-hand measuring cup. All measuring cups within 250ml are left-hand type, and those above 500ml are right-hand type

2. Thermometer

thermometer is an instrument used to measure temperature. There are many kinds of them, including digital thermometer, thermal thermometer and hemorrhoids. The temperature of glass liquid is often used in the laboratory

thermometers can be divided into standard thermometers and practical thermometers according to their use and measurement accuracy. The precision of standard temperature juice is high. 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, etc. Stick type industrial temperature juice is commonly used in middle schools. The range of alcohol thermometer is 100 ℃, and mercury thermometer has two range specifications of 200 ℃ and 360 ℃

precautions for use:

(1) choose a thermometer suitable for the measurement range. It is forbidden to use the thermometer beyond the range

(2) when measuring the liquid temperature, the vacuole of the thermometer should be completely immersed in the liquid, but should not contact the container wall. When measuring the steam temperature, the vacuole should be above the liquid level. When measuring the distillation distillate temperature, the vacuole should be slightly lower than the distillation flask branch pipe

(3) when reading, the line of sight should be level with the highest point (mercury thermometer) or the lowest point (alcohol thermometer) of the meniscus of the liquid column

(4) it is forbidden to use temperature juice instead of glass rod for mixing. After use, wipe it clean, put it into a paper cover, and store it away from heat source

3. tray balance

tray balance is an instrument used to roughly weigh the mass of substances. Each balance is equipped with a box of weights

there are two kinds of loads commonly used in middle school laboratories: 100g (sensitivity of 0.1g) and 200g (sensitivity of 0.2g). Load, also known as load capacity, refers to the maximum limit that can be weighed. The sensitivity refers to the balance error (). For example, a tray balance with a sensitivity of 0.1g means that its error is 0.1g, so it cannot be used to weigh objects with a mass less than 0.1g

precautions for use:

(1) before weighing, place the balance stably, move the traveling code to the left to the zero of the scale, and 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 successively when the pointer swings is close to the same. When the pointer is stationary, it should point to the center of the scale. If the swing of the balance is not balanced, the left and right screws can be adjusted to balance the swing

(2) the weighing material without injection pressure realizes low porosity and good adhesion between the insert and the overmolded polymer. It can be directly placed on the pallet. A piece of the same size paper should be placed on two pallets respectively, and then the reagent to be weighed should be placed on the paper for weighing. Wet or corrosive reagents must be weighed in glass containers (such as Watch glasses, beakers or weighing bottles)

(3) put the weighing object on the left disk, the weight on the right disk, and the weight should be clamped with tweezers. First add the weight with large mass, then add the weight with small mass, and finally move the weight until the pointer swings to balance

(4) after weighing, put the weights back into the weight box in turn. Move the code back to zero

(II) reaction instruments

1. Test tube

test tube is a reaction container used for a small amount of reagent, and it can also be used to collect a small amount of gas. Test tubes are often divided into flat mouthed test tubes, flip mouthed test tubes and supported test tubes according to their uses. Flat mouthed test tubes are suitable for general chemical reactions, and flip mouthed test tubes are suitable for adding rubber plugs. Test tubes with branches can be used as gas generators. First of all, marketing planning is needed to make a positioning and market distribution for the experimental machine, which can be used for gas bottle washing 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 l00mm, 12 l00mm, 15 l50mm, 18 180mm, 20 200mm and 32 200mm

precautions for use:

(1) when using test tubes, select test tubes of appropriate size according to different dosage. Use the test tube with your bare hands and hold the upper edge of the test tube with your fingers. The cantilever should not move during oscillation

(2) the heating of the liquid should not exceed the volume, and form a 45 angle with the desktop. The nozzle should not face yourself or others. To keep boiling, heat near the liquid level

(3) to contain powdery reagents, send them to the bottom of the tube with a paper trough. When containing granular solids, tilt the tube so that the particles slide slowly into the bottom of the tube along the tube wall

(4) hold the test tube at the place away from the nozzle. When heating, the outside of the test tube should be wiped dry, and the test tube cannot be heated by hand. After heating, pay attention to avoid sudden cooling to prevent cracking

(5) when heating solid reagent, the bottom of the pipe should be slightly higher than the nozzle. When it is finished, it should continue to be fixed or placed on asbestos to allow it to cool naturally

2. Beaker

beaker is usually used as a reaction container when there is a large amount of reactants, providing high-quality and low-cost biological high molecular varieties for downstream utilization. In addition, it is also used to prepare solutions, accelerate the dissolution of substances, and promote the evaporation of solvents. There are many kinds and specifications of beakers, and low beakers are commonly used in middle schools. In order to facilitate adding a certain amount of liquid during use, white volume marks are printed on the outer wall of some beakers, which are called marking beakers, and some are called graduated beakers. Its graduation is not very accurate, and the allowable error is generally 5%. Therefore, the word approx is printed on the graduation table, which represents the approximate volume. Therefore, it cannot be used as a gauge. The specifications of beakers are distinguished by volume, and commonly used are 50ml, 100ml, 250ml, 500ml, etc

precautions for use:

(1) the beaker should not contain too much solution, which is about the volume, but when heated, the solution should not exceed the volume

(2) the beaker cannot be burned dry. It can only be heated for a long time when it is filled with liquid, but it must be padded with asbestos

(3) when taking the beaker, take the outer wall and keep your fingers away from the inner wall. Take the beaker when heating, and use the beaker clamp

(4) when mixing the solution in the beaker with a glass rod, rotate the glass rod evenly along the wall of the beaker, and do not hit the wall and bottom of the beaker

(5) beakers should not be stored for a long time. They should be washed, wiped dry and stored upside down immediately after use

3. Flask

flask is a container with liquid participating in the reaction, which is used for many reactants and needs to be heated for a long time. Its neck diameter is small, and it is often used to generate steam or as a gas generator after being equipped with plugs and required accessories. Flasks are widely used, so there are many types. Round bottom flasks and flat bottom flasks are commonly used in middle schools

round bottom flasks are generally used as heating conditions. The soaring cobalt price forces battery manufacturers to consider new materials with high nickel as reaction vessels in the evolutionary direction. Flat bottom flasks are used for gas generators under unheated conditions, and are also commonly used for bottle washing. Because the flat bottom flask has a small plane at the bottom and edges, the stress is large and it is easy to burst when heated. Therefore, it is generally not used for reaction vessels under heating conditions

the specifications of the flask are distinguished by the volume, which are usually 150ml, 250ml and 500ml

precautions for use:

(1) the thickness of the bottom of the round bottom flask is relatively uniform, and there is no edge, which can be used for long-term strong heat use

(2) when heating, the flask should be placed on asbestos and cannot be heated directly with flame

(3) after the experiment, the heat source should be removed, and after static cooling, the waste liquid should be treated and washed

4. Distillation flask

distillation flask belongs to the flask class. The difference is that there is a slightly downward branch at the bottleneck, which is specially used as a container for distilled liquid

distillation flasks are divided into two categories: reduced pressure and normal pressure. There are also three kinds of atmospheric evaporated durian flasks with branch pipes on the bottleneck, the middle and the lower part. For the distillation of liquids with higher boiling points, the distillation flask with branch pipes on the lower part of the bottleneck is selected, and the distillation flask with branch pipes on the upper part of the bottleneck is used for those with lower boiling points. The branch pipe located in the bottleneck is often used to distill the liquid with general boiling point

the specifications of distillation flasks are different according to the volume, which are usually 150ml and 250ml2

precautions for making:

(1) when configuring accessories (such as thermometer, etc.), appropriate rubber plugs should be selected, and special attention should be paid to checking whether the air tightness is good

(2) when heating, it should be placed on asbestos to heat it evenly

5. Conical flask

conical flask is also called conical flask or triangular flask

the conical bottle has a large bottom and a small mouth. After the solution is filled, the center of gravity is lower, which is very convenient for hand-held oscillation. Therefore, it is often used as a titration container in volumetric analysis. It is also commonly used in laboratories to assemble gas generators or wash bottles

the size of conical flask is distinguished by volume, which is usually 150m1, 250ml, etc

precautions for use:

(1) during oscillation, hold the bottleneck with the right thumb, index finger and middle finger, gently hold the lower part of the bottleneck with the ring finger, relax the wrist, and drive the fingers with the palm to make a circular vibration

(2) when the conical flask needs to vibrate, the solution in the flask shall not exceed the volume

(3) if it is necessary to heat the liquid contained in the conical flask, asbestos must be padded

6. Qujingzhen

qujingping is also called qujingping or qujingzhen. It is a practical and simple instrument with a long history. Except for the only one with a ground glass stopper, the container is connected with qujingzhen, and the lines are smooth and complete at one go. It is used as a reaction vessel or distiller

the biggest advantage of the curved neck bottle is its simple structure. It can be connected with the glass container through the receiver, or directly with the inclined flask. There is no need to connect the rubber plug or rubber pipe between them, so it is corrosion-resistant. For example, when making nitric acid in the laboratory, solid sodium nitrate can be put into the cork first, and then appropriate concentrated sulfuric acid can be added to tighten the cork

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