Temperature dependence of crystal structure of Rochelle salt in the lo
wer paraelectric phase is studied by X-ray diffraction. Especially the
circumstances of the cations and behaviours of tartrate and water mol
ecules are presented. The shape and the orientation of tartrate molecu
le do not show temperature dependence in the lattice of potassium ions
. The tartrate molecules are tightly connected along the b-axis throug
h O(8) water molecule each other and they tightly conncted to potassiu
m atoms so that the tartrate molecules, O(8) water molecule and potass
ium atoms make a tight sheet parallel to the b-c plane. Also O(8) wate
r molecules contact to potassium atoms along the a-axis and the intera
tomic distances depends on temperature. The interatomic distance betwe
en O(9) and O(10) water molecules does not depend on temperature, howe
ver the pair of the water molecules rotate with temperature.