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Laboratory chemical analysis instrument operation skills summary! (1)

Daily laboratory operation skills, hope to give you help!

A.Glass instrument washing

Washing methods are summarized as follows:

1. Scrub with water:

It can wash the soluble material and make the dust attached to the instrument elute down.

2. Scrub with detergent or synthetic detergent:

It removes grease from the instrument.

3. Wash with concentrated hydrochloric acid:

It can be washed to remove oxidizing agents such as manganese dioxide from the wall.

4. Chromic acid lotion:

Add 8g finely ground industrial K2Cr2O7 to 100mL warm concentrated sulfuric acid and heat it with a small fire. Do not heat until white smoke comes out. Stir as you heat, cool and store in a fine-mouthed bottle.

Washing method:

1. Wash the glassware with water or washing powder.

2. Remove the water in the vessel as far as possible to avoid diluting the lotion.

3. Pour the lotion back into the original bottle for reuse.

The lotion is highly corrosive, do not splash on clothes and skin. Chromic acid washing liquid has strong acidity and oxidation, decontamination ability, suitable for washing oil and organic matter. When the color of the lotion turns green, the washing efficiency decreases and should be reformulated.

4. NaOH aqueous solution containing KMnO4: Dissolve 10gKMnO4 in a small amount of water, and inject 100ml 10% NaOH solution into the solution. The solution is suitable for washing oil and organic matter. After washing, MnO2 precipitation is left on the glassware, which can be washed off with concentrated HCl or Na2SO3 solution.

5. Hydrochloric acid-alcohol (1∶2) washing solution: suitable for washing with organic reagent stained colorimetric dish. The colorimetric dish should avoid using brush and chromate lotion.

The wall of the cleaned instrument shall be moistened with water and no droplets shall be attached to it.

After washing the instrument with the above method, after washing with tap water, there is still Ca2+, Mg2+ plasma. If you need to remove these ions, you should also use deionizing water for 2 ~ 3 times.

B.The use of chemical reagents

1. Use of solid reagent

Solid state reagents are usually taken with a spoon. The two ends of the medicine spoon are the size of two spoons, respectively to take a large amount of solid and a small amount of solid. Once the reagent is removed, it should not be poured back into the bottle. Excess reagent can be put into the specified container.

2. Use of liquid reagent

Liquid reagents are usually measured with a measuring cylinder or absorbed with a dropper. The following are their operations.

(1) Measuring cylinder

Gauges are available in 5,10,50,100 and 1000mL sizes. To remove the liquid, remove the cork and place it on the table. Hold the measuring cylinder in one hand and the bottle in the other (make sure the label is not down), and pour out the required amount of reagent. Finally, tilt the mouth of the bottle against the cylinder, and set the reagent bottle upright, so that the droplets left in the mouth do not flow to the outside of the bottle.

(2) Dropper suction

Squeeze the rubber nipple at the top of the dropper with your fingers to remove air from it, then release your fingers and inhale.

Do not insert the dropper into the container when the test liquid is dropped into the test tube. The dropper should only be used for special purpose and should be replaced after use. General dropper to take 1mL at a time, about 20 drops of test solution.

If more accurate measurements of liquid reagents are required, the instruments described below – burets and pipettes, etc.

C.Heating method

1. Alcohol lamp

Alcohol is inflammable, pay attention to safety when using, light with a lighter, and do not use another burning alcohol lamp to ignite, doing so, the alcohol inside the lamp will be spilled outside, make a lot of alcohol fire and cause an accident. When the spirit lamp is not in use, cover it so that the flame goes out. Do not blow it out with your mouth. Cover tightly to prevent the alcohol from evaporating.

When the need to add alcohol to the lamp, the flame should be extinguished, and then by means of a funnel to add alcohol into the lamp, the amount of alcohol to add 1/2 ~ 1/3 pot).

2. Alcohol blowtorch

Usage:

(1) Add alcohol

When adding alcohol, close the bottom switch, and the amount of alcohol stored in the lamp should not exceed 2/3 of the alcohol pot.

(2) preheating

Preheat dish add a small amount of alcohol to ignite, preheat after the alcohol vapor escape, you can ignite the lamp. If there is no steam, dredge the outlet of alcohol steam with a probe, preheat and ignite.

(3) regulation

The rotary regulator regulates the flame.

(4) put out

Can cover out, can also turn out the regulator.

Blowtorch use generally does not exceed 30min. Allow to cool and add alcohol before continuing.

3. The water bath

When the substance to be heated is required to be heated evenly and the temperature does not exceed 100℃, the water in the water bath is first boiled and heated with steam. The copper ring of different size can be placed on water bath to bear all kinds of utensils.

The following 4 points should be paid attention to when using water bath:

(1) Should try to keep the water bath tight.

(2)When the water in the copper water bath is boiled dry, the heating should be stopped immediately, and the water bath is cooled, and then the water is added to continue to use.

(3) Be careful not to soak the beaker directly in the water bath and heat it, which will cause the bottom of the beaker to break due to uneven heating in contact with the bottom of the water bath.

When using a water bath to heat the liquid in a test tube or centrifugal tube, a common water bath is a 250mL beaker. Fill with distilled water (or deionized water) and heat the water until it boils.

(4) Pay attention not to soak the beaker directly in the water bath and heat it, which will make the bottom of the beaker break due to the uneven heating of the bottom of the water bath.

When using a water bath to heat the liquid in a test tube or centrifugal tube, a common water bath is a 250mL beaker. Fill with distilled water (or deionized water) and heat the water until it boils.

4. Oil and sand baths

When the heated substance is required to be heated evenly and the temperature is above 100℃, an oil bath or a sand bath can be used. An oil bath is made by replacing water in a water bath with oil. A sand bath is an iron pan covered with a uniform layer of fine sand. First heat the iron pan and place the heated vessel on the sand. To measure the temperature of a sand bath, insert a thermometer into the sand.

5. Electrical heating

In the laboratory is also commonly used electric furnace, electric heating sleeve, tubular furnace and muffle furnace and other electrical heating. The heating temperature can be controlled by adjusting the external resistance. Both tube and Muffle furnaces can be heated to about 1000℃.