An ammonium-proton exchange in double-four-ring (D4R) spherosilicate [Si8O20][NMe4](8) with Meldrum's acid in N, N-dimethylacetamide afforded the corresponding silanol [Si8O12][OH](8) (1), which was purified successively by gel permeation chromatography and recrystallization. The singlecrystal X-ray diffraction analysis of 1, which is the first of its kind, unambiguously revealed the structure of 1. Silanol 1 obtained via this procedure does not contain water and could thus be treated with the moisture-sensitive chlorosilane Me2HSiCl to afford the corresponding silylated product [Si8O12][OSiMe2H](8).