1002.] Isomeric Change in Benzene Derivatives. 



157 



star-shaped aggregates, which are very soluble in water (S0 4 found 

 31*0, calculated 31*4 per cent.). $-TrichlorGbenzenediazonium nitrate, 

 Q.HoCla'N (N0 3 ):N, prepared in a similar manner, forms colourless 

 needles. When kept for two or three days, both salts begin to show 

 signs of change, which are more marked in the case of the nitrate. 

 The latter becomes noticeably yellow, and when dissolved in water 

 forms a yellow solution. The initially colourless aqueous solution 

 of the pure colourless salts becomes yellow after a few hours ; after 

 24 hours chloride is just recognisable in the solution. In one 

 experiment, 0*5 gramme of the acid sulphate was dissolved in 

 100 c.c. of water; after 3 days a very small amount of a yellowish-red 

 solid had separated from the yellow solution ; at the end of 16 days, 

 the chloride in solution was precipitated by silver nitrate in the 

 presence of nitric acid : the silver chloride weighed 0'05 gramme, 

 whereas for the complete conversion of the diazonium salt into 

 the diazophenol, 0'235 gramme of silver chloride should have been 

 found. 



An aqueous solution of s-trichlorobenzenecliazonium acetate, obtained 

 by mixing neutral solutions of the diazonium nitrate and sodium 

 acetate (molecular proportions) rapidly becomes yellow and acid. 

 In a short time the solution becomes turbid, and after 4 — 5 hours 

 deposits a bright yellow amorphous solid. In an experiment, in 

 which T75 gramme of the diazonium nitrate, dissolved in 150 c.c. of 

 water, was treated with sodium acetate (1 mol.), and kept at 10- — 15° 

 for 40 hours in the dark, an estimation of the hydrogen chloride in 

 the solution showed that 54*5 per cent, of the diazonium compound 

 had changed into the diazophenol. 



When instead of sodium acetate, sodium hydrogen carbonate was 

 used a similar change took place, but far more rapidly. In one 

 experiment a dilute aqueous solution of sodium hydrogen carbonate 

 (3 mol.) was added drop by drop during a period of 1 hour to a 

 cooled solution of 1 gramme of the diazonium hydrogen sulphate. (The 

 bicarbonate was finally present in sufficient quantity to combine with 

 the whole of the sulphuric acid and one-third of the chlorine present 

 in the diazonium salt.) After one-third of the bicarbonate had been 

 added, and the acid converted into the normal sulphate, the solution 

 rapidly became yellow and deposited a yellow solid. Throughout the 

 experiment the mixture was acid. As soon as the whole of the 

 bicarbonate was added, the chlorine was estimated ; it represented 

 54*5 per cent, of the amount which should be obtained were 1 atom 

 of chlorine eliminated from the diazonium salt. In another experiment, 

 using the same quantities of diazonium salt and sodium bicarbonate, 

 the solutions were mixed as rapidly as possible ; a copious yellow 

 precipitate at once appeared ; the chloride in the filtrate represented 

 72 per cent, of ] atomic proportion of chlorine. 



