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Simple and practical laboratory operation tips

Release date:2018-08-06  source:矿石化验  author:化学先生  Browse times:753
Storage of common chemicals

Nitric acid solidified iodine silver nitrate, low temperature dark brown bottle.

Liquid bromine ammonia water is volatile and should be sealed in a cool place.

White phosphorus storage requires cold water, potassium, sodium, calcium and kerosene.

Alkali bottles need to use rubber stoppers and plastic lead to store hydrogen fluoride.

The metamorphic drug is short-lived, flammable and explosive.

The desiccant in the laboratory, the wax seal preserves the heart.

Explanation:

1. Nitric acid solid iodine silver nitrate, low temperature dark brown bottle: It means that nitric acid, solid iodine and silver nitrate are all substances that are easily decomposed by heat, so they must be stored in a brown bottle and placed in a cool place.

2. The alkali bottle needs a rubber stopper: it means that the reagent bottle containing the alkali solution should use a rubber stopper.

3. Plastic lead storage of hydrogen fluoride: It means that hydrogen fluoride (hydrofluoric acid) is easy to corrode glass, so it must be stored in plastic or lead vessels.

4. The time of prone to change is short: it means that the deteriorating drug has a short storage time, that is, it cannot be stored for a long time, and it is best to use it now. [Lenovo: Common perishable drugs are:

1 If the hydrogen sulphuric acid is left for a long time, most of it will volatilize and partially be oxidized by air;

2 long-term storage of chlorine water will be invalidated due to slow decomposition;

3 long-term storage of ferrous salt, it is easy to be oxidized to iron salt;

4 acidified potassium permanganate solution will slowly fade after long-term storage].

5. Flammable and explosive sources: meaning flammable substances (such as: carbon disulfide, alcohol, acetone, benzene, sulfur, phosphorus, magnesium powder, etc.) and explosive substances (such as potassium chlorate, ammonium nitrate, etc.) Keep away from fire.

6. Desiccant in the laboratory, the wax seal preserves the heart: it means that the desiccant used in the laboratory is very easy to absorb water, so it should be stored with a wax seal.

Neutralization titration

The water washing machine is clearly cut, and the leak is checked and the air is adjusted again.

Add the reagent to the test solution, and control the right hand with the left hand.

The underside of the bottle is viewed from the paper, and the reading should be flat with the cut surface.

Phenolphthalein indicators are often known, strong acid weak base methyl orange.

Use an acid burette, not clear the alkali solution.

Explanation:

1. The water washing machine is clearly cut: "water" has two meanings here, which means tap water and distilled water; "liquid" also has two meanings here, which means both the standard solution and the liquid to be tested. This sentence means that in the middle and titration experiments, it is necessary to clean all kinds of instruments first, and when to use tap water, when to use distilled water, when to use standard liquid, and when to use the test liquid must be clearly distinguished. .

2. Checking the leak and then adjusting the zero: It means to check whether the burette leaks before titration, and then check if there is any bubble at the lower end of the burette. If it should be rushed off, finally adjust the liquid level to "0".

3. Adding reagent to the test solution: "Indicator" means an indicator. This means that 2-3 drops of indicator should be added to the conical flask containing the test solution before titration (the effect is to indicate the end of the reaction by its color change).

4. Left hand control right manual: means that in the timing of the titration, the burette must be controlled by the left hand, and the right hand-held conical flask is continuously shaken.

5. Under the bottle, the color of the paper: "Under the bottle" means that in order to clearly observe the change of color, a white paper can be placed under the conical flask; "eye color" means that During the titration process, you should keep an eye on the color change of the solution, and do not look at the scale of the burette.

6. The reading should be level with the cut surface: the reading should be flush with the lowest point of the concave surface.

7. Phenolphthalein indicator often knows, strong acid weak base methyl orange: This sentence means that the neutralization and titration of commonly used phenolphthalein as an indicator, only strong acid titration of weak base (such as hydrochloric acid titration of ammonia), can use methyl orange.

8. Use acid burette, not lye, remember: This sentence means that the acid burette can not be used to hold the alkali solution (because the lye and SiO2 in the glass react to form Na2SiO3, the piston and the burette stick together) .

Preparation of the substance concentration solution

Calculate the weighing step, dissolve and transfer to constant volume.

Do not forget to wash at room temperature, shake the label will be completed.

Explanation:

1. Calculate the weighing step, dissolve and transfer to constant volume: the meaning of these two sentences indicates that the steps of formulating the molar solution are: calculation, weighing, (or measuring), dissolving, transferring, and constant volume.

2. At room temperature, it is forgotten that "room temperature" means that the temperature of the solution is often increased by the exothermic heat of dissolution when it is dissolved, so it is necessary to transfer to a constant volume after cooling to room temperature. "Washing" means that after pipetting, the beaker and the glass rod must be washed with distilled water (2 to 3 times), and the washing liquid is incorporated into the volumetric flask, and then the volume is adjusted.

3. Shake the label and it will be: "Shaking" means to cover the stopper after the volume is fixed, use the index finger to hold the stopper, hold the bottom of the bottle with the finger of the other finger, and turn the volume bottle upside down and shake more. The solution is evenly mixed; the "label" means that the label is to be labeled, indicating the concentration of the solution and the date of preparation.

Filter operation experiment

The bucket glass bead is the same as the filter paper funnel.

Don't forget to wait until you filter.

Explanation:

1. Bucket beaker glass rod, filter paper funnel angle: "bucket" refers to the funnel; "frame" refers to the funnel rack. These two sentences illustrate the instruments required for the filtration operation experiment: funnel, funnel holder, beaker, glass rod, filter paper, and emphasize that the filter paper is folded at the same angle as the funnel (so that the filter paper fits snugly against the funnel wall).

2. Stand still before filtration: This means that the liquid must be allowed to stand for a while before filtration to separate the solid and liquid sufficiently.

3. Don't forget the three lows: the meaning is that you don't forget the three lows when filtering. “Three-way” means that the end of the funnel neck depends on the wall of the beaker that receives the filtrate. The glass rod is placed on the filter paper, and the beaker mouth of the filter liquid is placed on the glass rod; the meaning of “two lows” means It means that the edge of the filter paper should be slightly lower than the edge of the funnel, and the liquid level of the poured liquid should be slightly lower than the edge of the filter paper.

Distillation operation experiment

The cold pipe is heated by the net, and the lower edge of the upper edge is flat.

Need to add crushed porcelain to prevent bumping, hot air and cold water reverse.

Explanation:

1. Separate the net to cool the cold pipe: "cold pipe" this condensation pipe. This means that the asbestos mesh is required to heat the distillation flask (to prevent the distillation flask from rupturing due to uneven heating) and to tilt downward when installing the condenser.

2. The upper edge of the upper edge is two horizontal: it means that the upper edge of the mercury ball of the thermometer should be on the same level as the lower edge of the interface of the distillation tube branch.

3. Need to add crushed porcelain to prevent bumping: in the distillation process, it is necessary to add broken ceramics to prevent bumping.

4. Hot air cold water reverse line: It means that the cooling water should flow continuously from the bottom to the top, contrary to the direction of the flow of hot steam.

Extraction operation experiment

The extracts are insoluble in each other and the degree of solubility is not the same.

Shake it fully and then let it stand, and put it down and cut it clearly.

Explanation:

1. The extract solution is insoluble in each other, and the degree of solubility is different: "extraction agent" refers to an extractant; "quality" refers to a solute. The meaning of these two sentences is that in the extraction operation experiment, the principle of selecting the extractant is that the solvent in the extractant and the solution are mutually incompatible, and the solubility of the solute in the extractant and the original solvent is different (in the extractant) The solubility in the solution is greater than the solubility in the original solution).

2. Fully oscillate and then stand still: This means that the extraction should be fully oscillated during the extraction process to allow the extraction to be sufficient, and then allowed to stand to separate the solution.

3. Detach the cut and cut clearly: This sentence means that the lower layer of the separatory funnel is discharged from the funnel foot, and the upper liquid is poured out from the funnel.

 
 
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