Solubilities of Amino and Nitro Substituted Stilbene Sulfonic Acids: Investigations and Applications

The recovery of 4,4'-dinitrostilbene-2,2'-disulfonic acid (DNS) and 4,4'-diaminostilbene-2,2'-disulfonic acid (DSD) and the purification of 4-amino-4'-nitrostilbene-2,2'-disulfonic acid (ANSD) are important processes during their individual production. To increase the yields of DNS, DSD, and the purity of ANSD, detailed studies on the solubilities of these three stilbene sulfonic acids (SSA) are necessary. Herein, the static analytical method was used to investigate the effects of pH, temperature, and ionic strength on the solubilities of these three SSA. On the basis of the results, new processes were proposed to recover more DNS and DSD during their production. In addition, a new purification method was developed to obtain ANSD with a purity of > 99 %.