Preparation and production method of Eriochrome Black T

Preparation and production method of Eriochrome Black T

Based on the stable properties and easy solubility in water and ethanol of solid chromium black T indicator, water, 95% ethanol, glycerol, and triethanolamine can be selected as solvents respectively. When using water, 95% ethanol, or propylene glycol as solvents, 0.5g of chromium black T indicator must be added with 10ml of hardness buffer, then dissolved and diluted to 100ml with water, 95% ethanol, or propylene glycol, instead of following the same procedure? 9.1.3.6 of the hygiene standards for drinking water should be directly dissolved in 95% ethanol and diluted to 100ml. Dissolve 0.5g of chromium black T indicator in 100ml of triethanolamine using triethanolamine. A maximum of 25ml of ethanol can be used instead of triethanolamine to reduce the viscosity of the solution, as triethanolamine has amine alkalinity and does not require a hardness buffer. The above chromium black T indicator liquid indicator is stored in a brown bottle in the refrigerator for easy use. Among them, the chromium black T indicator aqueous solution can only be stored for a few days due to polymerization and oxidation reactions; Chromium black T indicator ethanol solution can only be stable for about a month due to the volatility of ethanol in the chemical book; Chromium black T indicator glycerol or triethanolamine solution can be stored for a longer period of time. Among the four solvents, triethanolamine is the best because it can not only slow down the polymerization rate of chromium black T indicator, but also act as a masking agent to eliminate the blocking effect of Fe3+and Al3+on chromium black T indicator when titrating Ca2+and Mg2+with EDTA-Na2. The chrome black T indicator is a deep purple red color, and the titration water sample also appears purple red. There should be no change in the color of the titration endpoint, and it does not function as an indicator; If the indicator is dropped into pure water, it will not appear the expected pure blue color, but rather a deep purple red color; If the indicator prepared above titrates the water sample, the color of the titration endpoint will change significantly. If dropped into pure water, it will appear pure blue, and the result will be verified to be consistent with the standard water sample. In practical work, we use triethanolamine as a solvent, prepared in a 0.5% ratio, and stored in a brown dropper bottle in the refrigerator. It can be used for 1-2 years.

Production method

The product is prepared by coupling 6-nitro-1,2,4-oxide (i.e. 6-nitro-2-hydroxy-1-diazonaphthalene-4-sulfonic acid) with 1-naphthol, followed by salt precipitation, filtration, drying and other flaking processes. The product has a uniform black brown powder on the outside, with a color light similar to the standard product (blue light gray → blue light black). The strength is 100 ± 3 (minutes) of the standard product, with a moisture content of ≤ 5%, a water-insoluble impurity content of ≤ 1%, and a fineness (residual content after passing an 80 mesh sieve) of ≤ 5%. The dyeing fastness on wool meets the standard product's requirements (sun fastness level 7, brown fastness to soap washing, water immersion, sweat stains, boiling, carbonization, ironing, dry cleaning, etc. are all 4-5 levels, and dry friction fastness level 3-4). Raw material consumption (kg/t) 6-nitro-1,2,4-oxide (100%) 500 naphthol (100%) 255 caustic soda (100%) 255 soda ash (industrial) 215 hydrochloric acid (31%) 675 refined salt 450.