Flow injection analysis of ethyl xanthate by gas diffusion and UV detection as CS2 for process monitoring of sulfide ore flotation.
A sensitive and robust analytical method for spectrophotometric determination of ethyl xanthate, CH(3)CH(2)OCS(2)(-) at trace concentrations in pulp solutions from froth flotation process is proposed. The analytical method is based on the decomposition of ethyl xanthate, EtX(-), with 2.0 mol L(-1) HCl generating ethanol and carbon disulfide, CS(2). A gas diffusion cell assures that only the volatile compounds diffuse through a PTFE membrane towards an acceptor stream of deionized water, thus avoiding the interferences of non-volatile compounds and suspended particles. The CS(2) is selectively detected by UV absorbance at 206 nm (epsilon=65,000 L mol(-1) cm(-1)). The measured absorbance is directly proportional to EtX(-) concentration present in the sample solutions. The Beer's law is obeyed in a 1x10(-6) to 2x10(-4) mol L(-1) concentration range of ethyl xanthate in the pulp with an excellent correlation coefficient (r=0.999) and a detection limit of 3.1x10(-7) mol L(-1), corresponding to 38 microg L(-1). At flow rates of 200 microL min(-1) of the donor stream and 100 microL min(-1) of the acceptor channel a sampling rate of 15 injections per hour could be achieved with RSD<2.3% (n=10, 300 microL injections of 1x10(-5) mol L(-1) EtX(-)). Two practical applications demonstrate the versatility of the FIA method: (i) evaluation the free EtX(-) concentration during a laboratory study of the EtX(-) adsorption capacity on pulverized sulfide ore (pyrite) and (ii) monitoring of EtX(-) at different stages (from starting load to washing effluents) of a flotation pilot plant processing a Cu-Zn sulfide ore.
Spectroscopic characterization of ethyl xanthate oxidation products and analysis by ion interaction chromatography
An ion interaction chromatographic separation method, coupled with UV spectroscopic detection, has been developed for the analysis of ethyl xanthate (O-ethyl dithiocarbonate) and its oxidative decomposition products in mineral flotation systems. The effects of the ion-pairing agent (tetrabutylammonium ion), pH modifier (phosphoric acid), and organic modifier (acetonitrile) in the eluant upon the retention characteristics of the ethyl xanthate oxidation products have been determined. The optimized separation procedure has been successfully applied to the analysis of ethyl xanthate and its oxidation products in a nickel-iron sulfide mineral suspension containing a number of other anionic species, including cyanide complexes of nickel and iron, as well as sulfur-oxy anions. The ethyl xanthate oxidation products investigated in this study have been isolated as pure compounds and characterized by UV-visible, FT-IR, and NMR spectroscopies. The UV-visible and FT-IR spectroscopic properties of these species are discussed in terms of the chemical modifications of the thiocarbonate group.
Hutcheson's Moral Sense Theory Reconsidered
There is no more central feature of Francis Hutcheson's moral philosophy than his theory of the moral sense. In the past this sense or faculty was widely understood to be a distinctive and independent sense devoted to the apprehension of moral qualities, but William Frankena has in recent years challenged this traditional view of Hutcheson's theory, and offered in its place an emotivist interpretation. Without question Frankena's study was of the first importance, in that it seems to have overturned the much too simplistic traditional view of the moral sense. Unfortunately, however, Frankena's own interpretation of the moral sense is as inadequate and misleading as the view he overturns, for he concludes that the moral sense is not at all a cognitive faculty, that it does not, that is, apprehend moral qualities, but, rather, is a faculty that enables and motivates us to feel, express, and evoke moral emotions. The moral sense, he argues, is “the source of the feelings involved” in moral approbation or disapprobation, and this approbation is “wholly non-cognitive, very much as it is on Ayer's more recent [emotivist] view … This, I shall show, is much too narrow a view; Hutcheson did not limit the moral sense to a single function, nor did he — lacking as he did twentieth-century perspectives — find it either necessary or desirable to assume that the domains of the cognitive and the emotive (or affective) were mutually exclusive.