C. Beevers, W. Hughes
Jul 1, 1940
Citations
0
Influential Citations
8
Citations
Journal
Nature
Abstract
WE have succeeded in finding approximate positions for all the atoms of Rochelle salt (sodium potassium tartrate tetrahydrate) in the crystal structure. The unit cell has dimensions 11.93 A. × 14.30 A. × 6.17 A. (Z = 4), and the space group is P21212. The set of general positions expressing this symmetry is and the co-ordinates of the various atoms are as follows (expressed in sixtieths of the cell edges): We are not satisfied with the accuracy of these positions; but we have no doubt that our general idea of the structure is correct. It agrees with two-dimensional Fourier syntheses projected down the a and b axes (the signs of the F's being obtained from intensity changes in the differently substituted salts) and also with a three-dimensional Patterson diagram of the ammonium salt, for which all the intensities were observed. All the interatomic distances are reasonable. The water molecules seem to be either of the three- or the four-bonded type. They coordinate the sodium and potassium atoms and assist in bonding these to the tartrate molecule. The tartrate molecule itself has an extended carbon chain with the two identical halves of the molecule lying in two planes inclined at 60° with one another.