The ir spectrum of K2C2O4·H2O is reported at liquid nitrogen temperature (LNT). On the basis of present work and earlier Raman studies, the frequencies at 3400, 3250, 1615, 1600, 1577, 1487, 1311, 902, 780, 605, 522, 449, 353, and 305 cm−1 have been assigned to the fundamental internal modes of C2O4 and H2O groups. In addition, the wagging and rocking modes of bonded water have been assigned unambiguously at 737 and 646 cm−1, respectively. Compared with the spectrum at room temperature, the spectral changes on cooling to LNT are as follows: (1) The bands at 522 and 1311 cm−1 each show splitting into two bands; (2) the librational modes of crystalline H2O show considerable increase in peak intensities accompanied by sharpening and a shift of about +20 cm−1; and (3) among the internal modes of H2O the symmetric stretching mode at 3250 cm−1 shows greater enhancement than the other two modes.
V. S. Tomar, H. D. Bist, and D. P. Khandelwal, "Infrared Spectrum of Potassium Oxalate Monohydrate at Liquid Nitrogen Temperature," Appl. Spectrosc. 24, 598-601 (1970)