Cleaning methods of the hottest chemical instrumen

2022-08-15
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Cleaning methods of chemical instruments

in the analysis work, washing glass instruments is not only a necessary preparation before the experiment, but also a technical work. Whether the washing of the instrument meets the requirements has an impact on the accuracy and precision of the test results. Different analytical work has different requirements for the cleaning of instruments. We mainly introduce the cleaning methods of instruments based on general quantitative chemical analysis

(I) cleaning agents and scope of use

the most commonly used cleaning agents are soap, soap liquid (special commodities), washing powder, decontamination powder, washing liquid, organic solvents, etc

soap, soap liquid, washing powder, decontamination powder, used for instruments that can be directly brushed with a brush, such as beakers, triangular bottles, reagent bottles, etc; Washing liquid is mostly used for instruments that are inconvenient for brush washing, such as burette, pipette, volumetric flask, distiller and other instruments with special shapes, as well as for washing cup utensils that are not used for a long time and scaling that cannot be brushed by the brush. Washing the instrument with washing liquid is to remove the dirt by using the chemical reaction between the washing liquid and the dirt. Therefore, it needs to soak a certain opportunity to play a full role; Organic solvents are aimed at the greasiness of certain types of dirt, which can be washed away with the help of organic solvents that can dissolve grease, or with the help of the particularity that some organic solvents can mix with water and play fast, washing the instrument with water will not wash away. For example, toluene, xylene, gasoline, etc. can be used to wash oil stains, and alcohol, ether, acetone can be used to wash freshly cleaned instruments with water

(II) precautions for the preparation and use of washing liquid

washing liquid is abbreviated as washing liquid, and there are various kinds of washing liquid according to different requirements. The commonly used ones are introduced as follows

1. Strong acid oxidant lotion

strong acid oxidant lotion is prepared with dichromate (K2Cr2O7) and concentrated sulfuric acid (H2SO4). K2Cr2O7 has strong oxidation ability in acid solution and has little corrosive effect on glassware. Therefore, this lotion is most widely used in the laboratory

the preparation concentration varies from 5% to 12%. The preparation method is roughly the same: take a certain amount of K2Cr2O7 (industrial product is OK), heat and dissolve it with about 1~2 times of water first, and then slowly add the volume required for the concentration of H2SO4 of industrial product into the K2Cr2O7 non solution (never add water or solution into H2SO4), stir it with a glass rod while pouring it upside down, and pay attention not to splash it, mix it evenly, and put it into a detergent bottle for standby after cooling. The newly prepared lotion is reddish brown and has strong oxidation capacity. When the lotion turns black and green after long use, it means that the lotion has no oxidizing washing power

for example, prepare 500ml of 12% lotion. Take 60g of industrial K2Cr2O7 and put it in 100ml of water (the amount of water added is not fixed, and the degree of solubility is taken as the degree), heat it for dissolution, cool it, slowly add 4340ml of concentrated H2SO4, stir it while adding it, and bottle it after cooling. What is worth mentioning is standby

when using this lotion, pay attention not to splash it on the body, so as to prevent "burning" clothes and materials from changing the experimental machine and damaging the skin. Pour the washing liquid into the instrument to be washed, and then pour it back to the washing liquid bottle after soaking the surrounding wall of the instrument for a while. After washing the newly soaked instrument with a small amount of water for the first time, the waste water should not be poured into the pool and sewer, which will corrode the pool and sewer for a long time. It should be poured into the waste liquid tank. When the tank is full, it should be poured into the garbage. If there is no waste liquid tank, when pouring into the pool, it should be washed with a large amount of water while pouring

2. Alkaline lotion

alkaline lotion is used to wash instruments with oil and dirt. This lotion is used by soaking for a long time (more than 24 hours) or soaking. Wear latex gloves when taking the instrument from the alkaline lotion to avoid burning the skin

commonly used alkaline washing solutions include: sodium carbonate solution (Na2CO3, i.e. soda ash), sodium bicarbonate (na2hco3, baking soda), sodium phosphate (Na3PO4, trisodium phosphate) solution, disodium hydrogen phosphate (Na2HPO4) solution, etc

3. Alkaline potassium permanganate lotion

using alkaline potassium permanganate as lotion, the effect is slow, and it is suitable for washing greasy vessels. Preparation method: take 4G of potassium permanganate (KMnO4) and add a small amount of water to dissolve it, and then add 100ml of 10% sodium hydroxide (NaOH)

development history of bending testing machine

4 Pure acid and soda wash

according to the nature of the dirt on the utensils, soak or boil the utensils directly with concentrated sulfuric acid (HCl), concentrated sulfuric acid (H2SO4) and concentrated nitric acid (HNO3) (the temperature should not be too high, otherwise the volatilization of concentrated acid will stimulate people). More than 10% concentrated caustic soda (NaOH), potassium hydroxide (KOH) or sodium carbonate (n2co3) solution is used for soaking or boiling utensils (which can be boiled)

5. Organic solvent

until the conditioning is qualified, the vessels with fatty dirt can be scrubbed or soaked with gasoline, toluene, xylene, acetone, alcohol, chloroform, ether and other organic solvents. However, using organic solvents as washing liquid wastes a lot, and alkaline washing liquid should be used as much as possible for large instruments that can be washed with a brush. Only small pieces that cannot use brushes or instruments with special shapes can be washed with organic solvents, such as piston bore, pipette tip, buret tip, buret plug hole, buret, vial, etc

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