Figure 1.

²⁷Al NMR solution spectra of Al₂(SO₄)₃ in L1 medium recorded at pH 3 to 7 and scaled to the signal with the highest intensity at 0.9 ppm (left) with the spectral region characteristic for the hexa-coordinated Al magnified (right). All spectra were recorded without ²H spin lock as no deuterated solvent was used. For all spectra, the background ²⁷Al signal due to the glass of the NMR tube was recorded in a separate experiment with the same number of scans and receiver gain and subtracted from the spectrum of the respective sample.