Two pure dehydrated borogermanates with microporous structure, beta-K-2[B2Ge3O10] and NH4[BGe3O8], have been synthesized and characterized by XRD, FT-IR, TG techniques. The molar enthalpies of solution of 2.51 mg of GeO2 (s)/0.99 mg of H3BO3 (s)/1.98 mg of H3BO3 (s) in 2.00 cm(3) of 1 mol . dm(-3) NaOH (aq) were measured, respectively. The molar enthalpies of solution of 2.44 mg of K2B4O7 center dot 4H(2)O (s) and 2.18 mg of NH4B5O8 center dot 4H(2)O (s) in the mixture solvent of 2.00 cm(3) of 1 mol . dm(-3) NaOH (aq) which contains 2.51 mg of GeO2 (s) were measured, respectively. The molar enthalpies of solution of 3.82 mg of beta-K-2[B2Ge3O10] (s) in the mixture solvent of 2.00 cm(3) of 1 mol . dm(-3) NaOH (aq) which contains 0.99 mg of H3BO3 (s), and 3.00 mg of NH4[BGe3O8] (s) in the mixture solvent of 2.00 cm(3) of 1 mol . dm(-3) NaOH (aq) which contains 1.98 mg of H3BO3) (s) were also measured, respectively. With the use of standard molar enthalpies of formation for NH4B5O8 center dot 4H(2)O (s), K2B4O7 center dot 4H(2)O (s), GeO2 (s), H3BO3 (s) and H-2 O (l), the standard molar enthalpies of formation of -(3937.1 +/- 4.7) kJ . mol(-1) for beta-K-2[B2Ge3O10] and -(2713.7 +/- 6.0) kJ . mol(-1) for NH4[BGe3O8] at T = 298.15 K were obtained on the basis of the appropriate thermochemical cycles, respectively. (C) 2015 Elsevier Ltd. All rights reserved.