L'ortho-oxy-phénylfluorone,réactif spécifique soit du molybdéne,soit du cuivre

The authors have extended their analytical research on methyl- and ethylfluorone to other derivatives of fluorone, amongst these o-oxyphenylfluorone.This compound is an excellent reagent for molybdenum and the reaction may be made specific for this element by a filter paper technique, The interfering colours, due to the elements As, Fe, V, Ge, Ti, Sn, and Sb are eliminated by using a 20% solution of KF. Under these conditions only copper interferes by giving an indigo-violet colour. By adding 0.5 N sulphuric acid this colour due to copper disappears, whilst that due to molybdenum is unchanged. This reaction, thus made specific for molybdenum, suffers interference only from the presence of oxidising agents which must be removed in a preliminary treatment.The violet colour due to copper, mentioned above, can be used for the detection of copper on the drop plate by treating with hydrogen peroxide which transforms Mo into a permolybdate and adding potassium, tartrate which forms a complex with cobalt. Under these conditions, only copper gives an indigo-violet precipitate and only salts of gold and ruthenium interfere, being precipitated as the metal by the action of H₂O₂. In the absence of these two noble metals (reduced by H₂O₂) the reaction may be considered as specific for Cu⁺².The limit of dilution of the reaction of Mo and Cu is the same and equal to D = 10^-1.5.