[en] The determination of the terminal temperature solubility of hydrogen in the zirconium alloys is a matter of our interest, since the hydride precipitation in these materials make them susceptible to the delay hydrogen cracking (DHC). Nowadays efforts are directed to the determination of this parameter on irradiated materials. In this frame we have begun a program to determine these curves on irradiated zirconium alloys like Zircaloys, Zr 2.5% Nb, Zr 1% Nb, zirconium sponge and high oxygen zirconium with different microstructures using the differential scanning calorimeter technique. The earlier task that we have imposed to us is the evaluation the reproducibility of this technique and the influence of the heating and cooling rates on the results. With these objectives we have initiated this work measuring the terminal temperature solubility (TTS) in unirradiated recrystallized and cold worked Zircaloy-4. We have found that the reproducibility of the technique is good; the average values (TSSD) and (TSSP) agree within the experimental error and the dispersions are low. Variance analysis indicates that the values of TSSD and TSSP do not depend on the heating and cooling rates. Within the rank analyzed the differences in the measurements are only possible to be attributed to statistical and/or experimental errors. The obtained curves of solubility show to a good agreement with the values obtained by others authors until 200 ppm (weight) of hydrogen. Similar comparisons between precipitation curves have not been made in regard to which these values depend on the maximum temperature reached in the experience. (author)