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Preparation of 25% sodium hydroxide (NaOH) aqueous solution takes caution and strict adherence to the instructions, as sodium hydroxide is quite caustic substance. Here is a step-by-step guide.
Materials and Equipment:
- Sodium hydroxide (NaOH) in form of granules or flakes;
- Distilled water;
- Glass container with heat-resistant glass or a plastic container;
- Precision scales for accurate weighing of NaOH;
- Protective gear: rubber gloves, safety goggles, and an apron;
- Spatula or glass rod for stirring;
Step 1: Safety Preparations
First of all, wear rubber gloves, safety goggles and an apron or chemical coat in order to avoid potential contact with sodium hydroxide. Prepare an acidic solution for neutralizing sodium hydroxide in case of skin contact (citric acid).
Step 2: NaOH Weighing
Use a scale to weigh a required amount of NaOH. For 100 ml the 25% solution, weigh 25 grams of NaOH.
Step 3: Water Preparation
In another clean glass or plastic container, prepare the necessary amount of distilled water. Usually, you’ll need a larger quantity of water (100 ml) than the weight of NaOH to ensure thorough mixing.
Step 4: NaOH Adding to Water
Add water to the solid NaOH slowly to avoid a vigorous exothermic reaction with splashing. Reach about 80 mL risk on the vessel. Stir slowly and gently using a spatula or glass rod.
Step 5: Dissolving NaOH
Continue stirring until all of the NaOH is completely dissolved in the water. It’s essential to avoid rapid stirring to prevent splashing. Add more water to reach 100 ml after complete NaOH dissolution.
Step 6: Cooling Down 25% Solution
After complete dissolution of NaOH, allow the solution to cool down to room temperature. You now have a 25% aqueous sodium hydroxide solution.
Step 7: Transfer and Storage
Transfer the prepared 25% sodium hydroxide solution into a tightly sealed glass or plastic container. Store it in a cool, dry place, away from children and pets.
For long-term storage of aqueous sodium hydroxide solution, which has a high alkaline pH, it is recommended to use containers made of polypropylene (PP) or polyethylene (PE).
Both of these types of plastics are highly resistant to most alkalis and can withstand the high pH of the solution without softening or melting. Polypropylene and polyethylene also exhibit good chemical resistance and durability.
Ensure that the chosen container is made from high-quality polypropylene or polyethylene to be confident in its resistance to alkalis. Additionally, it is advisable to check for markings on the container indicating its compatibility with alkalis or high-pH chemicals.
You have to always control plastic containers condition, avoid mechanical damage, and store them in a cool and dry place to prevent unwanted reactions and maintain container integrity.
Remember that alkali is a highly corrosive substance, so that follow safety measures and avoid contact with the skin, eyes and mucous membranes. A chemist has to know the correct actions in case of contact with an alkaline solution. If an accidental contact with alkali occurs on the skin, follow these steps:
Flushing with Water: Firstly, thoroughly flush the affected skin with a large amount of cold running water. This will help completely remove any residue of the solution and prevent further action of the alkali.
Immediate Neutralization: After washing, neutralize the alkali by rinsing the affected area with an slightly acidic solution. You can use a diluted acetic acid solution with water in a 1:10 ratio (1 part vinegar to 10 parts water). This will help to neutralize the caustic effects of the alkali. Gently and carefully rinse the affected area using a soft cloth or sponge.
Seek Medical Attention: Immediately after neutralization and rinsing, seek medical attention or call for emergency medical assistance. Remember that even if symptoms seem mild, it is essential to consult a medical professional as the effects of alkali exposure can be serious and may require medical intervention.
It is crucial to know how to respond correctly in case of an accident during working with corrosive substances like alkali. Take care of yourself and always prioritize safety.
You can watch an example of preparation an alkaline solution in our video.