The first-stage reaction in dyeing that builds the colourant on the cloth (for example naphthol dyeing). An aromatic amine is treated with sodium nitrite under acidic conditions to form a diazonium salt, which is reported to be unstable and to need ice-cooled handling at 5°C or below.
synthesis of the colourant on the fibre includes diazotization (as a class)contextual
Explains that reacting aniline or similar amines with sodium nitrite under acidic conditions produces a diazonium salt, and calls this reaction diazotization.
Describes the procedure of mixing an ice-cooled hydrochloric-acid solution of an aniline derivative with an ice-cooled aqueous sodium nitrite solution to form a diazonium salt.
Source: アゾ色素合成実験での二酸化窒素発生への注意 （杉山晴紀、大場茂, 2019） ・P2 3-1 学生実験の内容 ・textbook ・ checked against the source by AI
diazotization ・propertyThe diazonium salt is reported to be unstable and prone to decomposition, requiring low-temperature (ice-cooled, below 5°C) handling.contextual
States that the diazonium salt is unstable and releases nitrogen gas as it decomposes, so it must be handled at or below 5°C.
diazotization ・mechanismThis chapter reports a specific procedure in which the diazo component (an aniline derivative) was dissolved in concentrated sulfuric acid, cooled with cold water to 0°C, diazotized by adding 5 M sodium nitrite, and then reacted for one hour with vigorous stirring after adding a coupling agent (e.g. 1-naphthol) dissolved in 5 M sodium hydroxide.contextual
Scope: as the lab procedure reported in this chapter
Describes dissolving 2,4-dichloroaniline in concentrated sulfuric acid, mixing with cold water and cooling to 0°C, diazotizing by adding 5 M sodium nitrite, then adding 1-naphthol dissolved in 5 M sodium hydroxide with vigorous stirring for one hour.
If a small home-use electronic scale is used to weigh out about 0.2 g of sodium nitrite, does it actually show poor sensitivity/accuracy at that range, as found in the Keio study, and can this be checked by comparing several scales?🧪 testable at home
Sugiyama & Ohba (2019) found that a small electronic scale with 0.1 g resolution (Shimadzu PZ-200) had poor sensitivity to weight changes in the 0-0.2 g range, contributing to a nitrogen-dioxide incident. Comparing several household scales (kitchen scale, jewellery scale, etc.) weighing the same small item could check whether this sensitivity gap is common.
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experimental ・