Small-Angle X-Ray Scattering from Hydrolyzed Aluminum Nitrate Solutions

The solutions, which contained from 1 to 2.5 hydroxide ions added per aluminum ion, were studied immediately after preparation and also in the final equilibrium condition. Aggregates present in the freshly prepared solutions probably have a characteristic platelet shape. Mention is made of the possible importance of these platelet‐shaped aggregates to the structure of freshly precipitated aluminum hydroxide gel. Estimates of the size of the clusters present in the aged solutions were obtained in terms of the radius‐of‐gyration parameter. For solutions with OH/Al ion ratios between 1.5 and 2.25, the parameter had a constant value of 4.3 Å. This value is in good agreement with the calculated radius of gyration for the complex $[{\mathrm{Al}}_{13}{\mathrm{O}}_4(\mathrm{OH}{)}_{24}({\mathrm{H}}_2\mathrm{O}{)}_{12}{]}^{\text{7+}}$ .