94 Proceedings of the Royal Irish Academy. 



12. Coupling of Benzidinc-Sulphone-Disidphonic Acid with Pyrogallol. 



OH OH SOsNa S0 3 Xa 



I I _' _ 



HO—^ V-N = N— / \ / y~ N = N— / \— OH 



\so/ 



OH OH 



The method adopted was similar to that for the previous dihydroxyl 

 compounds. The benzidrne-sulphone-disulphonic acid having been tetrazotised 

 and added with constant stirring to a cold solution of 30 grams of sodium 

 carbonate, the solution of pyrogallol (21 grams) was added immediately. 

 During the addition the mixture was stirred vigorously, the stirring being 

 continued for eight hours afterwards. On standing overnight, the mixture 

 was heated to 80°C, and saturated with common salt, when the colouring 

 matter was precipitated. It was filtered at the pump, and purified for 

 analysis by repeated separations on cooling from hot dilute alcohol. The 

 purified compound is a chocolate-brown amorphous powder, giving a light 

 amber solution in water. It dyes cotton directly a buff' shade. 



•1030 substance gave 6*7 ctcs. moi6t nitrogen at 15°C. and 767 mm. P., 

 corresponding to N = 7*70, 

 M H li 14 N«Na 1 S 1 requires N = 7-7::. 



1"'. ' - Shi / 'jihone-Disulphonic Acid with Gallic Acid. 



COONa SOjNu SOjXu COONa 



HO-\/-OH ~\ SQ / HO-\/-OH 



OH 6Ul OH 



Gallic acid (21 grams) was dissolved in 100 c.cs. of water, and the solution 

 obtained by tetrazotifling 20"3graras of benzidine-sulphone-disulphonic acidwas 

 added with constant stirring, which was maintained mechanically for two days. 

 After the mixture had been stirred for half an hour a solution of 35 grams of 

 sodium carbonate was added, a few drops at a time, so that the whole was 

 used up by the end of the second day. After standing overnight the mixture 

 was heated to 80 C. and saturated with common salt when the dye-stuff was 

 precipitated. It was purified by repeated separations, on cooling from 

 hot dilute alcohol, and formed a dark-brownish amorphous powder soluble in 

 water to a light-brown solution. The colouring matter dyes cotton directly 

 a very light-brown. 



