In the analysis work, washing glassware is not only preparatory work before the experiment but also technical work. The cleanliness of laboratory glassware directly affects the experimental results and even determines the success or failure of the experiment.
Because the utensils are not clean or contaminated, they often cause large experimental errors, and even the opposite experimental results may occur. Therefore, for the laboratories of schools, research institutes, hospitals and factories and mines, the washing of the instruments is very important.
The washing liquid is referred to as the washing liquid, and various washing liquids are available according to different requirements. The more commonly used ones are as follows:
Strong acid oxidizer lotion
The strong acid oxidant lotion is formulated with methyl dichromate (K2Cr2O7) and concentrated sulfuric acid (H2SO4). K2Cr2O7 has a strong oxidizing ability in acidic solutions, and it has little erosion effect on glass instruments. So this lotion is the most widely used in the laboratory.
The concentration of the preparation varies from 5 to 12%. Chromium is carcinogenic, so be careful when formulating and using lotions. Two common methods are as follows:
1. Take 100mL of industrial concentrated sulfuric acid in a beaker, carefully heat, then slowly add 5g of potassium dichromate powder, stir while adding, wait until all dissolves and slowly cool, then store in the fine mouth bottle of the ground glass stopper.
2. Weigh 5g potassium dichromate powder, place it in a 250mL beaker, add 5mL water to dissolve it, then slowly add 100mL concentrated sulfuric acid, the solution temperature will reach 80 °C, wait for it to cool, and store it in the grinding glass bottle.
The lotion is a strong oxidant, but the oxidation is relatively slow. It takes only a few minutes to several hours to directly contact the vessel. After taking it out, it should be washed thoroughly with tap water 7 times – 10 times and finally rinsed with pure water for 3 times.
Precautions:
This kind of lotion should be carefully taken care of when it is used, so as not to “burn” the clothes and damage the skin. The washing liquid is poured into the glassware to be washed, and the peripheral wall of the glassware should be fully dipped and then stopped for a while and then returned to the washing bottle.
After rinsing the newly dipped glassware with a small amount of water for the first time, do not pour the wastewater into the pool and the sewer. It will corrode the pool and the sewer for a long time. It should be poured into the waste tank. When the tank is full, it will fall into the garbage. If not The waste liquid tank should be rinsed with a large amount of water while pouring into the pool.
Alkaline lotion
The alkaline washing liquid is used for washing oily materials, and the washing liquid is used for a long time (over 24 hours) soaking method or dip method. When taking the instrument from the alkaline lotion, wear latex gloves to avoid burning the skin.
Commonly used alkaline washing liquids are: sodium carbonate solution (Na2CO3, soda ash), sodium hydrogen carbonate (Na2HCO3, baking soda), sodium phosphate (Na3PO4, trisodium phosphate) solution, disodium hydrogen phosphate (Na2HPO4) solution and the like.
Soap washing liquid, alkali washing liquid, synthetic detergent washing liquid: It is the most commonly used cleaning agent, soap, soap liquid, washing powder, decontamination powder, and can be used for brushing directly with a brush, such as a glass beaker. Triangular flasks, reagent bottles, etc.; lotions are used for glassware that are inconvenient for brush scrubbing, such as burettes, pipettes, volumetric flasks, distillers, etc., and are also used for washing long-lasting cupware and brushes. No scaling. Washing the glassware with a lotion removes the dirt by chemically reacting with the dirt itself.
Therefore, it is necessary to soak a certain amount of opportunity; the organic solvent is a kind of greasy property to the dirt and can be washed away by the action of the organic solvent to dissolve the oil, or can be mixed with water by some organic solvent. The specialty, is rinse the glassware with water will not wash away. For example, toluene, xylene, gasoline, etc. can wash grease, and alcohol, ether, and acetone can wash the equipment just washed water.
Alkaline potassium permanganate lotion
It is used as a washing liquid with alkaline potassium permanganate, which is suitable for washing oily vessels.
Formulation: Take 4 g of potassium permanganate (KMnO4) and dissolve it with a small amount of water, then add 10 mL of 10% sodium hydroxide (NaOH).
Pure acid soda lotion
According to the nature of the dirt of the vessel, directly immerse or digest the vessel with hydrochloric acid (HCL) or concentrated sulfuric acid (H2SO4), concentrated nitric acid (HNO3) (the temperature should not be too high, otherwise the concentrated acid volatilizes people). Soda ash lotion is more than 10% concentrated caustic soda (NaOH), potassium hydroxide (KOH) or sodium carbonate (Na2CO3) solution soaked or immersed in the vessel (can be boiled).
Organic solvents
The vessel with fatty dirt can be scrubbed or soaked with an organic solvent such as gasoline, toluene, xylene, acetone, alcohol, chloroform or ether. However, it is wasteful to use an organic solvent as a washing liquid, and an alkaline washing solution can be used as much as possible for a large glassware that can be washed with a brush. Only small pieces or specially shaped glassware that cannot use brushes can be washed with organic solvents, such as piston bores, pipette tips, burette tips, burette piston holes, droppers, vials, etc.
A washing liquid
For the inspection of carcinogenic chemicals, in order to prevent damage to the human body, the decontamination solution for decomposing these carcinogenic substances should be used for immersion before washing and then washing.
The repellents often used in food inspections are:
1% or 5% sodium hypochlorite (NaOCL) solution, 20% HNO3 and 2% KMnO4 solution.
The 1% or 5% NaOCL solution is destructive to aflatoxin. After immersing the contaminated glass instrument with 1% NaOCL solution for half a day or immersing it with 5% NaOCL solution for a while, the effect of destroying aflatoxin can be achieved.
Method: take 100g of bleaching powder, add 500mL of water, stir evenly, and dissolve 80g of industrial Na2CO3 in warm water 500mL, then mix the two liquids, stir, clarify and filter, the filtrate contains NaOCL is 2.5%; For powder preparation, the weight of NaCO3 should be doubled and the resulting solution concentration is approximately 5%. If a 1% NaOCL solution is required, the above solution can be diluted in proportion.
20% HNO3 solution and 5% KMnO4 solution have a destructive effect on benzo(a)pyrene. The glassware contaminated with benzo(a)pyrene can be soaked in 20% HNO3 for 24 hours. After taking it out, the residual acid is washed away with tap water. Washing is carried out. Latex gloves and micro-syringes contaminated with benzo(a)pyrene can be soaked in a 2% KMnO4 solution for 2 hours and then washed.
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