Single crystals of Rb-1.12(NH4)(0.88)S4 . Te(OH)(6) were obtained by slow evaporation at 300 K. Differential scanning calorimetry showed an anomaly at 418 K, two shoulders at 482 and 510 K and one strong peak at 517 K. X-ray diffraction shows that the first DSC peak at 418 K passes the material from paraelectric to ferroelectric phase. A conductivity study shows that the shoulder at 482 (which masks a second one at about 458 K) can be attributed to a superprotonic phase transition. Dielectric constant and dissipation factor evolutions indicate that the peak at 458 K is probably due to a ferroelectric-paraelectric phase transition. The strong peak at 517 K was attributed to the decomposition of the salt.