Washing liquid, referred to as detergent or lotion, is often used for glassware that is not easy to brush with brushes, such as burettes, pipettes, volumetric flasks, retorts, etc. It is also used for washing crapware that has not been used for a long time and fouling that the brush can not clean. The principle of the washing liquid washing glassware is that the washing liquid itself chemically reacts with the dirt, and then the dirt is removed. Therefore, when washing the glassware, the glassware needs to be immersed in the washing liquid for a certain period of time in order to fully function.
According to different experimental requirements, there are a variety of different lotions, and there are several more commonly used ones.
- Chromic acid lotion
The chromic acid washing liquid, also known as the strong acid oxidizing agent washing liquid, is prepared by using dichromate (K2Cr2O7) and concentrated sulfuric acid (H2SO4). K2Cr2O7 has a strong oxidizing ability in an acidic solution and has little erosive effect on glassware, so this lotion is most widely used in the laboratory.
Chromium has carcinogenic effects, so be careful when formulating and using lotion. The two preparation methods are as follows: (1) Take 100mL of industrial concentrated sulfuric acid in a beaker, carefully heat, and then slowly add 5g of heavy chromium.
The potassium acid powder was stirred while being added, and after being completely dissolved and slowly cooled, it was stored in a fine-mouthed bottle of a ground glass stopper.
(2) Weigh 5g of potassium dichromate powder, place it in a 250mL beaker, add 5mL of water to dissolve it, then
Then slowly add 100mL of concentrated sulfuric acid, while stirring, stir with a glass rod, and be careful not to spill, mix evenly, after cooling, wait for it to cool and store in a fine glass bottle.
For the prepared solution, the label should be labeled, indicating the name of the solution, the formulator, and the preparation time. The newly prepared lotion is reddish brown and has a strong oxidizing power. When the washing liquid turns black and green for a long time, it means that the washing liquid has no oxidative washing power.
Do not pay attention to this kind of lotion when it is used, so as not to “burn” the clothes and damage the skin. When the washing liquid is poured into the glassware to be washed, the peripheral wall of the glassware should be fully immersed and then stopped for a while and then returned to the washing bottle.
After rinsing the newly dipped instrument with a small amount of water for the first time, do not pour the waste water into the pool and the sewer to prevent corrosion of the pool and sewer for a long time. It should be poured into the waste tank. If there is no waste tank, pour into the pool. When you are over, rinse with plenty of water.
2. 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 (NaHCO3, baking soda), sodium phosphate (Na3PO4, trisodium phosphate) solution, disodium hydrogen phosphate (Na2HPO4) solution and the like.
3. Alkaline potassium permanganate lotion
The use of alkaline potassium permanganate as a washing liquid, the action is slow, suitable for washing oily vessels, and the manganese dioxide residue can be washed away with concentrated sulfuric acid or sodium sulfite solution.
Formulation: Take 4 g of potassium permanganate (KMnO4), add a small amount of water to dissolve, and then add 10 mL of 10% sodium hydroxide (NaOH).
4. pure acid soda lotion
According to the nature of the dirt of the vessel, directly immerse or digest the vessel with concentrated sulfuric acid (HCl) or concentrated sulfuric acid (H2SO4), concentrated nitric acid (HNO3) (the temperature should not be too high, otherwise the strong acid volatilization is strong). 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).
5. 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-sized glassware that can be washed with a brush. Only small or special-shaped glassware that cannot use brushes can be washed with organic solvents, such as piston bores, pipette tips, burette tips, burette piston bores, droppers, vials, etc.
6. decontamination
For the inspection of carcinogenic chemicals, in order to prevent damage to the human body, the decontamination solution that destroys these carcinogenic substances should be used for immersion before washing and then washed.
The decontas often used in food testing are 1% or 5% sodium hypochlorite (NaOCl) solution, 20% HNO3 and 2% KMnO4 solution.
1% or 5% NaOCl solution has a destructive effect on 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 Na2CO3 should be doubled and the resulting solution concentration is about 5%. If a 1% NaOCl solution is required, the above solution can be diluted in proportion.
20% HNO3 solution and 2% 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.
If you’re in need of information or have any questions, please contact WUBOLAB, the laboratory glassware manufacturer.
