Definition of Nessler's reagent: refers to the reagent used to determine the ammonia nitrogen content in air and water by using the principle of infrared-visible spectrophotometry. Properties: The transparent solution with yellowish green at room temperature will gradually turn yellow, except for the yellow-brown precipitate gradually generated with the increase of exposure time. Anti-mechanism: Under strong alkaline conditions, iodine ions and mercury ions will react with ammonia to generate red-brown colloidal compounds, which are strongly absorbed at the wavelength of about 420nm. The amount of this reddish-brown colloidal compound will be directly proportional to the absorption value of its solution, so the content of ammonia nitrogen can be determined by testing the absorption value of the reaction solution. Preparation method: there are two kinds of 1, 60g of potassium hydroxide is weighed, dissolved in about 250ml of ammonia-free water, and cooled to room temperature. In addition, 20 g of potassium iodide was weighed and dissolved in 100 ml of ammonia-free water, and the crystal powder of mercuric dichloride (about 10 g) was gradually added while stirring. When the red precipitate is not easy to dissolve, drop saturated mercuric dichloride solution instead and keep stirring. When a small amount of red precipitate is not easy to dissolve, stop dropping saturated mercuric dichloride solution. Then, the solution was slowly injected into the cooled potassium hydroxide solution, fully stirred while injecting, diluted to 400ml with ammonia-free water, and then left to stand overnight. Finally, the supernatant of the solution was transferred to a polyethylene plastic bottle and stored in the dark at room temperature. 2. Weigh 16g sodium hydroxide, dissolve it in 50ml ammonia-free water, cool it to room temperature, weigh 10g mercuric iodide and 7g potassium iodide and dissolve them in water, then slowly inject the solution into the above sodium hydroxide under the condition of full stirring, release it to 100ml with ammonia-free water, put it in polyethylene plastic bottles, and store it in the dark at room temperature. Precautions for use: 1. Mercury in Nessler's reagent is toxic, so be careful when using it, and wash it in time when the skin comes into contact with it. 2. Nessler's reagent has a short service life, and the shelf life after preparation is usually only three weeks, which will affect the determination results with the increase of precipitation. 3. When preparing the solution, all the water should contain no ammonia, and it can't be filtered by ordinary filter paper, otherwise it will easily pollute Nessler's reagent. Congo red Congo Red: English name: Congo Red Other names: cotton red direct red; Direct Congo red; Red; Direct vermilion; Diphenyl -4,4'-bis [(azo -2-)-65438+ o-aminonaphthalene -4- sodium sulfonate] Molecular formula: C32H22N6Na2O6S2 Molecular weight: 696.68 Property: brownish red powder. It turns yellow and red when it is dissolved in water; Orange when dissolved in alcohol; Very slightly soluble in acetone; Clear bright red solution. Almost insoluble in ether. The maximum absorbance (PH7.3 7.3,488 488nm,1%1cm) is 595. Uses: Acid-base indicator (Congo red is acidic indicator, the color change range is 3.5 to 5.2, the alkaline state is red, and the acidic state is blue-purple) adsorption indicator, and the verification of boric acid, cyanide and hydrochloric acid. Protein precipitation, embryo section, plant mucin, cellulose and elastic tissue staining. Storage and transportation conditions: sealed and preserved. Other names of Congo red (contrast agent): cotton red direct red; Direct Congo red; Red; Direct vermilion; Diphenyl -4,4'-bis [(azo -2-)-65438+ o-aminonaphthalene -4- sodium sulfonate] Main component: Congo red. Description: This product is a clear bright red solution. Indications: used to diagnose amyloidosis. No more than 40% is excreted from plasma within 1 hour after injection, and urine excretion is not significant. If the excretion in plasma exceeds 60% and the excretion in urine is still not significant, there may be amyloidosis. If there is a large amount of Congo red in urine, it means that there may be tubular fatty lesions or similar lesions. Administration and dosage: intravenous injection: 0. 1g each time. Adverse reactions and precautions: it may cause cancer; There may be a risk of harming the fetus. Whether to use medical insurance drugs: whether to use non-medical insurance drugs or over-the-counter drugs: other prescriptions: 1. This product is a clear bright red solution. If it is slightly precipitated, it is toxic and cannot be used. 2. Avoid compatibility with sodium chloride or glucose solution. Scientists at Harvard Medical School reported in Nature on 23rd that Congo Red, a dye commonly used in medical experiments, can prevent some abnormal protein accumulation in the brain, thus preventing Huntington's disease. Huntington's disease is a genetic disease, which usually occurs between the ages of 30 and 50. The patient's cells mistakenly produced a harmful substance called Huntington protein. These abnormal protein clusters, damaging some brain cells, especially those related to muscle control, leading to uncontrollable convulsions and developing into dementia. Congo red is a common cell marker dye in medical experiments. When researchers examine brain slices of Huntington's disease patients, they usually dye them with Congo red. Congo red can adhere to abnormal proteins and clearly show the aggregation area of protein blocks. The experiment of brain cell tissue culture conducted by scientists from Harvard Medical College shows that Congo red dye can not only attach to abnormal protein block, but also slow down the accumulation process of protein, and brain cells treated with Congo red are not easy to die. The experimental mice with Huntington's disease gene have less neurological dysfunction after receiving Congo red dye injection. Scientists say that this discovery provides a new method for treating Huntington's disease, but further research and improvement are needed before this method is applied to clinic. Congo Red is also used to mark abnormal protein in brain diseases such as Alzheimer's disease and Roitz's Felt-Jacob disease, so it may also help to prevent and treat these diseases. Grice's reagent: Formula for testing nitrite: (1) Dissolve 0.5g p-aminobenzenesulfonic acid in 50m l 30% acetic acid under heating, and store it away from light. (2) Mix 0.4 g 1- naphthol and 100 ml of water and boil, and add 6 ml of 80% acetic acid into the colorless solution poured from the blue residue. Mix (1) and (2) in equal volumes before use. References:
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