Fluoboric acid test paper

To the filtrate add 3 M sodium hydroxide solution and shake the flask to allow all of the acetic anhydride and fluoboric acid to react with the base. Test the aqueous layer with indicator paper to ascertain that neutralization is complete and then transfer the mixture to a reaction tube and draw off the aqueous layer. Wash the ether once with 10 mL of water, once with 10 mL of saturated sodium chloride solution, and dry the ether over anhydrous sodium sulfate, adding the drying agent until it no longer clumps together. 

Dissolve 46-5 g. (45-5 ml.) of aniUne in a mixture of 126 ml. of concentrated hydrochloric acid and 126 ml. of water contained in a 1-htre beaker. Cool to 0-5° in a bath of ice and salt, and add a solution of 36-5 g. of sodium nitrite in 75 ml. of water in small portions stir vigorously with a thermometer (1) and maintain the temperature below 10°, but preferably at about 5° by the addition of a httle crushed ice if necessary. The diazotisation is complete when a drop of the solution diluted with 3-4 drops of water gives an immediate blue colouration with potassium iodide - starch paper the test should be performed 3-4 minutes after the last addition of the nitrite solution. Prepare a solution of 76 g. of sodium fluoborate (2) in 150 ml. of water, cool, and add the chilled solution slowly to the diazonium salt solution the latter must be kept well stirred (1) and the temperature controlled so that it is below 10°. Allow to stand for 10 minutes with frequent stirring. Filter... 

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