Cleaning of analytical vessels

Generally, it can be cleaned with dilute acid or chromic acid, or by brushing!

Our laboratory uses a cleaning solution based on chromic acid. The preparation method is as follows: 5 grams of potassium dichromate are moistened with a small amount of water, and then 80 milliliters of concentrated sulfuric acid is added slowly while stirring; heating can be used to facilitate dissolution.

Flasks, Erlenmeyer flasks, reagent bottles, etc. can be cleaned by dipping a brush in washing powder or detergent and using it to scrub the surfaces. For instruments that are difficult to clean or cannot be scrubbed, such as burettes, pipettes, and volumetric flasks, they should be soaked in a cleaning solution before being rinsed clean; organic contaminants that are hard to remove can be washed away using organic solvents.

What was said upstairs is absolutely correct. As a supplementary note: if contaminated by specific organic substances, a dedicated solvent or a broad-spectrum solvent should be used for dissolution and cleaning before proceeding with regular cleaning.

First, soak it in an organic solvent or in a sodium hydroxide ethanol solution, then wash it with water. After that, wash it with chromic acid solution, again with water, and finally with distilled water; it is ready after drying

We usually use boric acid for cleaning!

The most convenient way to wash glassware on a daily basis is to use soap powder, detergent, etc. along with a brush for cleaning, and then rinse it sequentially with tap water and distilled water. On the surface of the cleaned glassware, a thin layer of water film should form when rinsed with distilled water ； If small water droplets remain, the surface has not been cleaned properly. For utensils that are difficult to clean with a brush or cannot be cleaned thoroughly, the following cleaning solution can be prepared for chemical cleaning. For the vessels used in the analysis of certain trace metals, after washing, they need to be soaked for a sufficient period of time in solutions of hydrochloric acid or nitric acid at certain concentrations, or in solutions containing chelating agents, in order to remove the metal ions adsorbed on their surface; thereafter, they are rinsed thoroughly with distilled water. Polyethylene, polyvinyl chloride, and polytetrafluoroethylene containers can also be cleaned in the same way, but it is necessary to be aware that plastic products are prone to deformation when heated, can be scratched by hard objects, and are sensitive to many organic solvents. (1) Chromic acid solution: Weigh 92 g of sodium dichromate dihydrate and dissolve it in 460 mL of water, then add 800 mL of sulfuric acid. Another formula involves adding 1 L of sulfuric acid to 35 mL of saturated dichromic acid solution. When the cleaning solution turns green, it loses its cleaning power. When using chromic acid cleaning solution, the vessels to be cleaned should contain as little water as possible, ideally being dry, to prevent the solution from being diluted and thus reducing its effectiveness. Potassium dichromate can also be used in place of sodium dichromate, but the former has a lower solubility. Containers washed with chromic acid solution must be thoroughly rinsed with clean water to remove any residual chromium ions. (2) Alkaline solution of potassium permanganate: A small amount of potassium permanganate is dissolved in a sodium hydroxide solution with a concentration of 100–200 g/L. It is suitable for washing oily glassware, but the remaining manganese dioxide precipitate must be removed using hydrochloric acid or hydrochloric acid combined with hydrogen peroxide. (3) Sodium (potassium) hydroxide ethanol solution: Adding about 1 L of 95% ethanol to a 120 mL aqueous solution containing 120 g of sodium (potassium) hydroxide results in a detergent with strong cleaning power; glass joints exposed to this solution for long periods are prone to damage. (4) Mix of sulfuric acid and fuming nitric acid: Suitable for particularly oily and dirty glassware. (5) Trisodium phosphate solution: Dissolve 57 g of trisodium phosphate and 28 g of sodium oleate in 470 mL of water. To remove carbonaceous residues from glassware, soak the ware in this solution for a few minutes and then use a brush to remove the residues. Sodium (potassium) hydroxide solutions at 100–150 g/L have the same effect. (6) 20 g/L sodium hydroxide solution containing 10 g/L EDTA: Soaking the cleaned glassware in this solution can remove some trace metal ions adsorbed on the surface of the containers. (7) Ethanol hydrochloride solution: a mixture of 1 part hydrochloric acid and 2 parts ethanol, used to wash vessels stained with organic reagents.

1. Method of washing new glassware: Newly purchased glassware contains a high amount of free alkali, and should be soaked in an acid solution for several hours first. Acid solutions generally use 2% hydrochloric acid or cleaning solution (see section “3” of this section). Rinse thoroughly with tap water after soaking. 2. Method of washing used glassware: (1) Test tubes, petri dishes, Erlenmeyer flasks, beakers, etc. can be scrubbed with a bottle brush or sponge dipped in detergents such as soap, laundry detergent, or cleaning powder, and then thoroughly rinsed with tap water. Hot soapy water has a stronger cleaning power and can effectively remove oil stains from utensils. Detergent and cleaning powder are difficult to rinse off completely, often leaving a layer of tiny particles on the surfaces of utensils; therefore, it is necessary to rinse them thoroughly multiple times, sometimes even more than 10 times. Alternatively, they can be shaken with dilute hydrochloric acid once, then rinsed with water, after which they should be placed upside down in a wire frame or on a wooden rack with hollow grids to dry indoors. In case of urgent need, it can be placed in a frame or an enamel tray and dried in an oven. After washing glassware, if the water on the inner surface is evenly distributed in a thin layer, it indicates that the oil residue has been completely removed; if water droplets remain, the ware needs to be soaked in cleaning solution for several hours before being thoroughly rinsed with tap water. The vessels containing solid culture medium should first have the solid material scraped off, and then washed. Contaminated utensils should be soaked in a 2% cresol soap solution (Lysol) or a 0.25% chlorhexidine disinfectant for 24 hours, or boiled for half an hour, before being washed using the above method. Cultures containing pathogens should first be autoclaved, after which the culture fluid should be poured off and the culture washed. Vessels used for preparing standard culture media can be used after being washed in the aforementioned manner. If precise preparation of chemical reagents or accurate experiments for research are required, they should first be rinsed with tap water, then washed three times with distilled water, and finally dried or baked before use. (2) Glass pipettes that have been used to draw blood, serum, sugar solutions, or dye solutions (including capillary pipettes) should be immediately placed in a measuring cylinder or specimen bottle filled with tap water after use, to prevent difficulty in cleaning them once they dry out. The bottom of the measuring cylinder or specimen bottle should be lined with absorbent cotton; otherwise, the pipette is likely to get damaged when inserted. Wait until the experiment is complete before rinsing all at once. If the top of the straw is packed with cotton, before rinsing, first connect the tip of the straw to the rubber tube attached to the faucet in order to flush out the cotton with water; afterwards, place it in the automatic straw washer for further rinsing. Laboratories that do not have an automatic straw washer can use the method of flushing out the cotton to rinse it several more times. Rinse with distilled water if necessary. After washing, place it in an enamel tray to dry; to speed up drying, it can be placed in an oven. Syringes that have been used to draw up microbial cultures should also be immediately placed in a measuring cylinder or specimen bottle containing a 2% cresol soap solution or a 0.25% benzalkonium chloride disinfectant; they can be removed for rinsing only after 24 hours. If there is oil residue on the inner wall of the straw, it should also be soaked in cleaning solution for several hours before being rinsed. (3) Used slides and coverslips: If these are coated with cedar oil, they should first be wiped clean with crumpled paper or soaked in xylene and shaken several times to dissolve the oil residue. After that, they should be boiled in soapy water for 5–10 minutes, wiped with a soft cloth or absorbent cotton, rinsed immediately with tap water, then soaked in a dilute cleaning solution for 0.5–2 hours. The cleaning solution should be rinsed off with tap water, and finally the slides and coverslips should be washed several times with distilled water. Once dry, they should be stored in 95% alcohol. When using it, burn off the alcohol over a flame. The slides and coverslips washed and stored using this method are clean, transparent, and free of water droplets. Slides or coverslips containing viable bacteria should first be soaked in a 2% cresol soap solution or a 0.25% benzalkonium chloride solution for 24 hours, and then washed and stored as described above. 3. Preparation and use of the cleaning solution (1) Preparation of the cleaning solution: There are two types of cleaning solutions – concentrated and dilute. The formulas are as follows: Concentrated solution: Sodium dichromate or potassium dichromate (industrial grade): 50g; Tap water: 150ml; Concentrated sulfuric acid (industrial grade): 800ml. Diluted solution: Sodium dichromate or potassium dichromate (industrial grade): 50g; Tap water: 850ml; Concentrated sulfuric acid (industrial grade): 100ml. In both cases, sodium dichromate or potassium dichromate is first dissolved in tap water; the mixture can be heated slowly to facilitate dissolution. After cooling, concentrated sulfuric acid is added gradually while stirring. The prepared cleaning solution should be brownish-red or orange-red. Store in a covered container. (2) Principle: Sodium dichromate or potassium dichromate reacts with sulfuric acid to form chromic acid; butyric acid has a very strong oxidizing ability, which gives this solution a highly effective cleaning effect. (3) Precautions for use: (a) The sulfuric acid in the cleaning solution is highly corrosive; leaving glassware in it for too long can damage the glass. Therefore, be sure not to forget to remove the ware and rinse it afterward. Secondly, if the cleaning solution gets on clothes or skin, it should be washed immediately with water, followed by washing with soda water or ammonia solution. If it splashes on tables or chairs, it should be washed away immediately with water or wiped off with a damp cloth ； (b) Glassware should be as dry as possible before being used, to prevent dilution by cleaning solutions ； (c) This liquid is intended for use only on glass and porcelain containers; it is not suitable for metal or plastic containers ； (d) Containers containing a large amount of organic matter should first be scrubbed before being treated with the cleaning solution; this is because excessive organic matter accelerates the degradation of the cleaning solution. Moreover, although the cleaning solution is a powerful detergent, it cannot remove all types of stains ； (e) The container holding the cleaning solution should always be covered to prevent oxidation and deterioration ； (f) The washing solution can be reused, but it becomes ineffective and should no longer be used once it turns dark green.

Ordinary glassware can be cleaned by dipping a brush in cleaning powder； For those that still remain stubbornly, soak them in chromic acid and repeat the above steps ； Of course, since crucibles can withstand high temperatures, we also use a muffle furnace at high temperatures to eliminate it completely.

It has dirt on it; brush it off if possible. If it cannot be brushed off, soak it in hydrochloric acid at a 1:1 ratio for an extended period of time, and then rinse it thoroughly with tap water and distilled water in sequence.