How to clean test glassware

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How to clean test glassware

as we all know, in chemical experiments, after the chemical reaction of glassware containing reactive substances, there are often residual impact resistant substances attached to the inner wall of the instrument. Some glassware heated at high temperature or placed with reactive substances for a long time is not easy to clean. Using unclean instruments will affect the experimental effect, and even let the experimenter observe the wrong phenomenon and conclude and infer the wrong conclusion. Therefore, the glassware used in chemical experiments must be washed clean. The following illustrates the points for attention in washing glass instruments with examples, so as to achieve the washing effect of turning difficulties into easy ones

first, choose a suitable detergent

in general, you can choose a commercially available synthetic detergent to clean glassware. When insoluble substances are attached to the inner wall of the instrument and cannot be cleaned with synthetic detergent, appropriate detergent should be selected according to the nature of the attachments. If the attachment is alkaline, dilute hydrochloric acid or dilute sulfuric acid can be selected to make the attachment react and dissolve; If the attachment is acidic, sodium hydroxide solution can be selected to make the attachment react and dissolve; If the attachment is a substance that is not easily soluble in acid or alkali, but is easily soluble in some organic solvents, such organic solvents are selected as detergents to dissolve the attachment

take a few examples: there are white attachments on the inner wall of the container of Jiusheng lime water, and dilute hydrochloric acid is used as detergent; Do iodine sublimation experiment. Purple black iodine is attached to the bottom of the container containing iodine, and soak it with potassium iodide solution or alcohol; There are dark brown attachments on the container wall of Jiusheng potassium permanganate solution, and concentrated hydrochloric acid can be used as detergent; The inner wall of the instrument is attached with a silver mirror, and nitric acid is used as detergent; If the inner wall of the instrument is stained with oil dirt, use hot soda solution to clean it

in the laboratory, there is also a specially prepared detergent that can be reused for many times

for vessels that are inconvenient to be cleaned with a brush or are not clean, the following cleaning solution can be prepared for chemical cleaning. For the vessels used to analyze some trace metals, after washing, they need to be soaked in a certain concentration of hydrochloric acid, nitric acid solution or a solution containing complexing agent for a considerable time to remove the metal ions adsorbed on the surface, and then rinse them with distilled water

polyethylene, polyvinyl chloride and polytetrafluoroethylene vessels can also be cleaned in the same way, but attention should be paid to the characteristics that plastic products are easy to deform when heated, easy to be scratched by hard objects and sensitive to many organic solvents

1. Chromic acid lotion: weigh 92g sodium dichromate dihydrate and dissolve it in 460ml water, and then inject 800ml sulfuric acid. Another formula is to inject 1L sulfuric acid into 35ml saturated sodium dichromate solution

when the lotion turns green, it loses its washing ability. When using chromic acid washing solution, the washed utensils should have less water, preferably dry, so that the washing solution will not be diluted and the efficiency will be reduced. Potassium dichromate can also be used to replace sodium dichromate, but the solubility of the former is low. The containers washed with chromic acid lotion should be fully rinsed with clean water to remove the possible chromium ions

2. Alkaline potassium permanganate washing solution. Weigh 4.0g potassium permanganate and put it in a 250ml beaker, then weigh 10.0g sodium hydroxide and put it in the same beaker. Measure 100ml distilled water, add it in several times and stir constantly to fully dissolve potassium permanganate and sodium hydroxide. Carefully transfer the dissolved part into a 200ml Brown reagent bottle, and repeat the operation until all potassium permanganate is dissolved. Rinse the beaker repeatedly with distilled water, and pour the rinsing solution into the brown reagent bottle until there is no purple red on the inner wall of the beaker. Finally, dilute the X-ray fluorescence in the second layer with the remaining distilled water, and analyze the elements between f-u to 100ml qualitatively and quantitatively. Close the cork, shake it well, and stick the label for standby. It is suitable for washing glassware with oil stains, but the remaining manganese dioxide needs to be washed away with hydrochloric acid or hydrochloric acid plus hydrogen peroxide

3. Sodium hydroxide (potassium) ethanol solution: add about 1l95% ethanol to 120ml aqueous solution containing 120g sodium hydroxide (potassium), which becomes a detergent with strong decontamination power. The glass mill mouth is easy to be damaged after long-term exposure to this lotion

4. Mixture of sulfuric acid and fuming nitric acid: suitable for particularly greasy and dirty glassware

5. Trisodium phosphate solution: dissolve 57g trisodium phosphate and 28g sodium oleate in 470ml water. To remove the carbon residue on the glassware, soak the glassware in this solution for a few minutes, and then remove the residue with a brush. 100 ~ 150g/l sodium hydroxide (potassium) solution also has the same effect

6, 20g/l sodium hydroxide solution of 10g/ledta: the glass ware soaked and cleaned with this solution can remove some trace metal ions adsorbed on the surface of the container except for the watch of the manufacturer of Milacron uniloy, ossberger and Aoki machinery

7. Hydrochloric acid ethanol solution: a mixture of one part of hydrochloric acid and two parts of ethanol, which is used to wash vessels stained with organic reagents

8. Acid oxalic acid lotion. Weigh 10g oxalic acid or 1g hydroxylamine hydrochloride and dissolve it in 20% 100ml hydrochloric acid solution. This lotion can be used for vessels stained with oxides and inorganic dirt dissolved in water (such as potassium permanganate, ferric iron)

second, master the operation method of glass washing instruments

for simple instruments with easily removable substances, such as test tubes. Beakers, etc. are brushed with a test tube brush dipped in synthetic detergent. Turning or. When moving the test tube brush up and down, use appropriate force to avoid damaging the instrument and scratching the skin

then rinse with tap water. When the instrument is inverted, the wall of the instrument forms a uniform water film, and there are no drops of water, nor streams of water, that is, it has been cleaned

for glassware with attachments that are difficult to remove, after dissolving the attachments with appropriate detergent, remove the washing residue, then brush with a test tube, and finally rinse with tap water

some glassware with fine and complex structure cannot be brushed with a brush, such as volumetric flask, pipette, etc., which can be soaked with detergent

limited to space, now take the acid burette as an example to introduce its washing operation as follows: at the beginning of washing, check whether the rubber disc on the piston is fastened to prevent it from slipping and damaging during washing; Pay attention to whether there is water leakage or blockage. If there is, adjust it. Close the piston, inject 2 ~ 3 ml of washing solution into the buret, slowly tilt the buret to the level, and slowly rotate the buret so that the inner wall is soaked with washing solution. Erect the burette, unscrew the piston, and discharge the washing liquid, so that the human segment of the piston can also be washed. Finally, rinse with tap water and discharge from the sharp nozzle at the lower part of the piston. Do not pour the liquid out of the upper nozzle to save time

the cleaning standard is as described above

III. wash the glassware in time

washing the glassware in time is conducive to selecting the appropriate detergent, because it is easy to judge the nature of the residue at that time. In some chemical experiments, the residual liquid after reaction is poured in time, and there is no attachment on the inner wall of the instrument that is difficult to remove. However, after being put aside for a period of time, the volatile solvent escapes, and there are residues attached to the inner wall of the instrument, making washing difficult. There are also some substances that the manufacturer should add to the corresponding control system to react with the instrument itself. If they are not washed in time, the instrument will be damaged or even scrapped

students experiment with "neutralization titration" all the basic burets, which are generally put aside for a long time after use. If they are not washed in time, the residual lye will act with the glass tube and the latex tube, causing the latex tube to deteriorate and crack, so it cannot be used. Moreover, the latex tube adheres to the root of the glass tube and the glass tip, which is difficult to peel off and replace. The author once tried to mix 37% hydrochloric acid into a 1:1 solution, immerse the glass tube and the part of the glass tip adhered to the residue of the latex tube, take it out after a period of time, wash the acid with tap water, and then it is easier to peel it off and reassemble. However, it consumes reagents, materials and time

IV. other precautions

do not blindly mix various reagents as detergents, and do not arbitrarily use various reagents to wash glassware. This is not only a waste of drugs, but also prone to danger

therefore, proper cleaning of glassware is a serious and important thing

China glass () Department

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