1. The most commonly used cleaning agents and their scope of use The most commonly used cleaning agents are soap, synthetic detergent (such as washing powder), lotion (cleaning liquid), organic solvents, etc. Soap, synthetic detergent, etc. are generally used for instruments that can be directly brushed with a brush, such as flasks, beakers, reagent bottles and other non-metering and non-optical glass instruments. Soap and synthetic detergent can also be used for titration 1. The most commonly used cleaning agents and their scope of use The most commonly used cleaning agents are soap, synthetic detergent (such as washing powder), lotion (cleaning liquid), organic solvents, etc. Soap, synthetic detergent, etc. are generally used for instruments that can be directly brushed with a brush, such as flasks, beakers, reagent bottles and other non-metering and non-optical glass instruments. Soap and synthetic detergent can also be used to wash burettes, pipettes, measuring bottles and other measuring glass instruments, but they cannot be scrubbed with a brush. The lotion is mostly used for glass instruments that cannot be cleaned with a brush, such as burettes, pipettes, measuring bottles, colorimetric tubes, glass melting funnels, Kjeldahl flasks and other glass instruments with special requirements and shapes; also used for washing for long periods of time The dirt on the glass instruments and brushes cannot be removed. 2. Preparation and description of lotion preparation of chromic acid cleaning solution: method 1 method 2 potassium dichromate (sodium) 10g 200g purified water 10ml 100ml (or appropriate amount) concentrated sulfuric acid 100ml 1500ml Preparation method: weigh the prescribed amount of dichromium Potassium acid, grind finely in a dry mortar, add this fine powder to a glass container with an appropriate amount of water, heat, stir to dissolve, after cooling, put the glass container in a cold water bath, slowly intermittently add concentrated sulfuric acid Add, stirring constantly, do not make the temperature too high, the color of the container's content gradually darkens, and pay attention to cooling, until the addition is complete and mixed, it is ready. Description: (1) Sulfuric acid can produce a strong exothermic reaction when it meets with water, so after the potassium dichromate solution has cooled, add the sulfuric acid slowly, stirring while adding, and do not operate in the opposite direction to prevent explosion. (2) The cleaning fluid is specially used for cleaning glassware. The reason for its decontamination and pyrogen effect is that the product has a strong oxidizing effect. When potassium dichromate meets concentrated sulfuric acid, it produces chromic anhydride with strong oxidizing effect: K2CrO7+H2SO4→H2CrO7+K2SO4 2CrO3+H2O→Cr2O3+3[O] Concentrated sulfuric acid is an oxyacid, which has an oxidizing effect at high concentrations. , The effect is more pronounced when heating: H2SO4→H2O+SO2+[O] Δ K2CrO7+3SO2+H2SO4→Cr2(SO4)3+K2SO4+H2O (3), the size of the cleaning effect of chromic acid depends on the size of the chromium produced in the reaction The amount of anhydride (CrO3) and the concentration of sulfuric acid. The more chromic anhydride, the stronger the acid and the better the cleaning effect. (4) Before cleaning the glass instrument with cleaning fluid, it is best to rinse the instrument with water to wash out most of the organic matter, and air dry the instrument as much as possible, so as to reduce the consumption of cleaning fluid and avoid dilution and lower efficiency. (5) This product can be used repeatedly, but the oxidizing effect has been lost when the solution is green, and it cannot be reused, but it can be renewed and reused. Renewal method: take the waste liquid to filter out the impurities, and slowly add potassium permanganate powder with constant stirring, about 6-8g per liter, until the reaction is completed and the solution turns brown. Let stand for precipitation, pour the supernatant, heat below 160℃ to evaporate the water, get a thick brown-black liquid, let it cool, add an appropriate amount of concentrated sulfuric acid, mix well to dissolve the precipitated potassium dichromate, spare. (6) Sulfuric acid is corrosive, so be careful when preparing. (7). Washing the instrument with chromic acid cleaning solution is to use it to react with the dirt to wash away the dirt, so it must be soaked for a certain period of time, usually overnight (according to the situation); sometimes it can be heated to make There are opportunities for full effect. 3. Methods and requirements for washing glass instruments (1) General glass instruments (such as flasks, beakers, etc.): first rinse with tap water, then scrub with soap and washing powder with a brush, then rinse with tap water, and finally purify Rinse with water 3 times (should be flushed along the wall and shaken sufficiently to improve the flushing effect). Measuring glass instruments (such as burettes, pipettes, measuring bottles, etc.): They can also be washed with soap and detergent, but not with brushes. (2) Precision or difficult-to-wash glass instruments (burettes, pipettes, measuring flasks, colorimetric tubes, glass melting funnels, etc.): Rinse first with tap water, drain, and then treat with chromic acid cleaning solution for a period of time (Generally leave it overnight), then rinse with tap water, and finally rinse with purified water 3 times. (3). When washing the instrument, first wash your hands with soap to prevent the oily dirt on your hands from sticking to the wall of the instrument and increase the difficulty of washing. (4). A clean glass instrument should be free of water droplets (when the cleaned instrument is turned upside down, there should be no water droplets on the wall after the water flows out). Second, drying of glass instruments (1) Drying instruments that are not urgent, etc., can be placed on the instrument rack and dried naturally in a dust-free place. (2) The instruments used in emergency, etc. can be dried with a glass instrument airflow dryer (the temperature is preferably 60～70℃). (3) The measuring glass instrument should be drained naturally, and cannot be baked in an oven. 3. Custody of glass instruments should be stored in the test cabinets in different categories, and they should be placed securely, and tall and large instruments should be placed inside. For grinding instruments that need to be stored for a long time, put a piece of paper between the plugs to avoid sticking for a long time.
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