Figure 6. Results of 7 experiments performed using 6 different highly-enriched 18O water portions (A – F in table 3), for determining δ 18O SLAP. The black circles represent the results using the first approach, where VSMOW was mimicked in δ 18O only. The black open squares represent the results obtained using the second approach where VSMOW was mimicked in both isotopes. The overall weighted mean of all data points is -56.33 ± 0.03‰ (including the Student T-factor). The error bars reflect the combined uncertainty calculated using a Monte Carlo approach, taking into account all individual error sources in the abundances, in the isotopic measurements and in the weights.