The conversion of primary aromatic amines into diazonium salts is known as ___________.

Hint:When primary amines are treated with a cold solution of nitrous acid generated in situ by the addition of sodium nitrite to the primary amine solution, then a bright coloured dye is formed that is called a diazo dye.

Complete answer:
The process of formation of the diazo compounds is called diazotization. The reaction was first reported by Peter Griess in the year 1858 who subsequently discovered several reactions of this new set of compounds. Most commonly diazonium salts are prepared by the treating a mixture of primary aromatic amine with sodium nitrate and dilute hydrochloric acid in the temperature range ${{\left( \text{0-5} \right)}^{\text{0}}}\text{C}$ as the diazo dyes dissociate at warm temperatures.
Hence, the conversion of the primary aromatic amines into diazonium salts is known as Diazotization reaction of Diazo coupling reaction.

Note:
The diazo compounds serve as intermediates in organic reactions and different other compounds can be formed from them.
When diazonium salts are treated with dilute hypophosphorous acid, ethanol, or sodium stannite gives benzene. When diazonium salts are treated with water and then it is heated then phenols are formed. Nitrobenzene can be obtained by treating benzenediazonium fluoroborate with sodium nitrate in presence of copper nitrate. Cyano groups cannot be introduced by nucleophilic substitutions of the haloarenes but such compounds can be prepared from diazo salts using cuprous cyanide and the reaction is called “Sandmeyer Reaction''. The aryl group in the diazo salt can be introduced by its reaction with benzene in the presence of sodium hydroxide.