Formation Constants of Protonated Amidinothiourea

The reactions of amidinothiourea NH₂ -(S=) C-NH-C (=NH).NH₂ with metal ions¹ and their analytical applications^2-5 are reported in the literature, but the protons-tion of amidinothiourea has not yet been investigated. The protonation reaction may be represented as follows:

                              B + H⁺  \(\rightleftharpoons\)    BH⁺ 

                              BH⁺+ H⁺ \(\rightleftharpoons\)  \(BH^{++}_2\)

whero B represents a molecule of amidinothiourea. The first (K₁) and the second (K₂) formation constants of protonated amidinothiourea are given by

                         \(K_1 = {[BH^+] \over [B][H^+]}\)           and                       \(K_2 = {[BH_a^{4+}] \over [BH^+][H^+]}\)

at constant ionic strength.