and hydrogen confirmed that the stoichiometry of this phase was absd l lysine 2 2 71 u00d7 10 u2212 3 mole of absd zwitterion anhydrous were added to 5 42 u00d7 10 u2212 3 mole of naoh and the mixture was dissolved in 2 ml of water then crystallization was forced by adding an anti solvent ethanol in large excess 30 ml after filtration the solid was analyzed by xrpd the obtained spectrum is presented in fig4 this xrpd pattern proves that a new phase has been crystallized it should be the disodium salt of absd a tga dsc analysis coupled to mass spectrometry was performed on this salt in order to observe its thermal behavior and to determine its water content the corresponding spectrum is presented in fig5 according to this analysis this phase loses water between 30 and 40 u00b0 c this phase is not an interesting alternative to the zwitterionic form because it exhibits the same kind of thermal stability problem crystallization of the sodium hydrogen salt of absd was performed as follows 2 71 u00d7 10 u2212 3 mole of absd zwitterion anhydrous were added to 2 71 u00d7 10 u2212 3 mole of naoh only a single sulfonic function of absd was then neutralized and the mixture was dissolved in a.