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The crystal structure of sodium sesquicarbonate (trona) has been determined completely. The crystals are monoclinic, space group C2/c, with cell dimensions a = 20.41 ± 0.03; b = 3.49 ± 0.01; c = 10.31 ± 0.01 A.; ![[beta]](/logos/entities/beta_rmgif.gif)
= 106° 20' ± 10'. The approximate atomic co-ordinates were found by means of a two-dimensional Patterson synthesis followed by the systematic comparison of structure amplitudes. These co-ordinates have been refined by means of three-dimensional Fourier syntheses, using 650 experimental structure amplitudes. The carbonate ion is found to be planar, with 120° angles, within experimental error; the C-O distances are 1.23 ± 0.02; 1.23 ± 0.02 and 1.26 ± 0.02 A., the last oxygen being bonded by a hydrogen bridge of 2.53 A. to an oxygen of another carbonate ion, forming what might be called a complex [HC2O6]3- anion. The water molecule has hydrogen bonds of lengths 2.72 ± 0.03 and 2.77 ± 0.03 A. to oxygen atoms of carbonate ions.
= 106° 20' ± 10'. The approximate atomic co-ordinates were found by means of a two-dimensional Patterson synthesis followed by the systematic comparison of structure amplitudes. These co-ordinates have been refined by means of three-dimensional Fourier syntheses, using 650 experimental structure amplitudes. The carbonate ion is found to be planar, with 120° angles, within experimental error; the C-O distances are 1.23 ± 0.02; 1.23 ± 0.02 and 1.26 ± 0.02 A., the last oxygen being bonded by a hydrogen bridge of 2.53 A. to an oxygen of another carbonate ion, forming what might be called a complex [HC2O6]3- anion. The water molecule has hydrogen bonds of lengths 2.72 ± 0.03 and 2.77 ± 0.03 A. to oxygen atoms of carbonate ions.
