Xanthate solutions of pH 6-10, prepared from "aged" potassium ethyl xanthate crystals, KEtX, were investigated spectrophotometrically in the region 190-400 mp and showed coexistence of xanthate ions, EtX-, dixanthogen, (EtX)z, and carbon disulphide, CS2. Optical density measurements on the spectra of dixanthogen solutions led to the evaluation of: molar absorptivities of dixanthogen a t wavelengths corresponding to the two main bands in the xanthate ion spectrum, i.e. a t 301 mP-6130 liter/mole cm, and a t 226 mp-18,400 liter/mole cm; the solubility of dixanthogen, ca. 1.3XlO-j mole/liter; and the equilibrium constant, k = 3 X 10l0, of the reaction 2(EtX)? + 40H---t 4EtX-+ 2H20 + 0 2 , for solutions saturated with air a t atmospheric pressure. Simultaneous reactions leading t o decomposition of xanthate and/or dixanthogen species to alcohol and carbon disulphide have been detected by a strong band a t 206.5 mp due to CS2 (with an estimated molar absorptivity of the order of 60,000-70,000 liter/mole cm).The behavior of xanthates in solution (particularly their dissociation, decomposition on acidification, and oxidation) has been the subject of numerous investigations. Yet, owing t o the complexity of the xanthate systems, many aspects have not been clarified. 111 the recent papers of Majinla (1, 2) the relevant literature is reviewed and new data are presented (based on ultraviolet spectrophotometry) concerning the dissociation, decomposition, and stability constants of alkyl xanthates from methyl to amyl, and lead, nickel, and cobalt xanthate complexes. Solubilities of numerous metal xanthates have been correlated in great detail by Sheka and Kriss (3) while Wronski (4) discusses the effects of increased pH in xanthate solutions.In investigating the kinetics of xanthate adsorption from mixed solutions containing quaternary ammonium compounds the use of ultraviolet spectrophotometric analyses of these mixed solutions necessitated a preliminary study of various products of xanthate decomposition. The most probable reactions involved in the decomposition of xanthate solutions are hydrolysis and formation of xanthic acid, [I]; decomposition to alcohol and CS2, [ 2 ] ; and oxidation to dixanthogen, [3]:Of these reactions, the production of xanthic acid and the subsequent decomposition to alcohol and CS2, particularly in low pH regions, have been most recently studied by Iwasaki and Cooke (6), Kleiil et al. (7), and Majima (1). The oxidation t o dixanthogen has been considered irreversible and of little interest, particularly since tests with 0 2 bubbled through xanthate solutions indicated this to be a slow reaction (Iwasaki and Cooke (6), Rao and Patel (8)) ; dixanthogen itself has been considered insoluble in water and no analytical method appears to be available for accurate determination of small quantities of dixanthogen.
'On leave from the Institute
