196 PRACTICAL ORGANIC CHEMISTRY tiously with shaking to 150 ml. of water, and to the hot solution so obtained, add 24 mi. (24-5 g.) of aniline. If all the aniline sulphate thus formed does not dissolve, warm the mixture gently until a clear solution is obtained. Now pour the solution into 200 ml. of cold water contained in a 600 ml. flask, and cool the mixture in ice-water until the temperature falls to 5°. (Some aniline sulphate may crystallise out again at this stage. This does not interfere with the reaction, however, because the sul-phate separates as very fine crystals which rapidly redissolve as the reaction proceeds.) Dissolve 20 g. of sodium nitrite in 50 ml. of water, and add this cautiously to the aniline sulphate solution, carrying out the diazotisation with the precautions described in the preparation of iodobenzene (p. 184). When all the sodium nitrite solution has been added, allow the solution to stand at room temperature for 15 minutes to ensure complete diazotisation, and then place the flask
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