Analytical applications of some flotation techniques-a review.

A review is given of the principles and more recent applications of foam flotation.

Determination of Mo(VI) in tap-water and sea-water by differential-pulse polarography and co-flotation.

A new method is described for the microdetermination of Mo(VI) in natural waters and sea-water by differential-pulse polarography based on the catalytic wave caused by Mo(VI) in nitrate medium following preconcentration by co-flotation on Fe(III) hydroxide. In the case of sea-water samples, hexadecyltrimethylammonium bromide (HTAB) was used together with octadecylamine as the surfactant. For the analysis of natural water samples only HTAB is needed. Molybdenum in the range 0.7-5.7 ng/ml has been determined.

A study of behavioural groupings of polyphenolic species in "fino" sherry wine. Evolution during vinification and mechanical treatment of the grape.

The different groups and/or classes among phenolic acids and aldehydes identified during the elaboration process of "fino" sherry wine have been studied. The study was carried out using different processes during the elaboration of the wine and we have attempted to establish whether the different treatments of the grape affect these groupings. The study was undertaken by means of cluster and multifactorial analysis on the data obtained by the quantitative determination of phenolic acids and aldehydes during vinification and in experiments carried out on the grape under different mechanical treatments. The analysis of phenolic acids and aldehydes was done with HPLC, using a C-18 mu-Bondapak and a stepwise composite gradient. The samples were previously extracted with ethylic ether.

Simultaneous separation of copper, cadmium and cobalt from sea-water by co-flotation with octadecylamine and ferric hydroxide as collectors.

A method is proposed for the simultaneous quantitative separation of traces ofCu(II), Cd(II) and Co(II) from sea-water samples by means of the co-flotation (adsorbing colloid flotation) technique with ferric hydroxide as co-precipitant and octadecylamine as collector. The experimental parameters have been studied and optimized. The drawbacks arising from the low solubility of octadecylamine and the corresponding sublates in water have been avoided by use of a 6M hydrochloric acid-MIBK-ethanol (1:2:2 v v ) mixture. The results obtained by means of the proposed method have been compared with those given by the usual ammonium pyrrolidine dithiocarbamate/MIBK extraction method.

A new type of labile palladiazo-pd(II) sandwich(?) compound formed in non-complexing aqueous media.

The formation of a labile, presumably "sandwich" type, complex of palladium(II) and palladiazo has been disclosed by differential spectrophotometry. The complex, which is formed within 10 min of mixing of the pertinent solutions, decomposes progressively over a period of 1-2 days to yield an ML complex. The ML(2) complex exhibits an "anomalous" absorption spectrum with two absorption bands with maxima located at 525 (secondary) and 660 (principal) nm, the latter giving a molar absorptivity of 7 x 10(4) l.mole(-1).cm(-1). Possible structures are suggested for the ML(2) and ML complexes.

Ion-exchange investigation of the arsenazo III-uranyl system: confirmation of the physical existence of a weak M(2)L-type new complex compound.

Ion-exchange experiments have proved the physical existence in the arsenazo III uranyl system of an M(2)L complex species in addition to the well-known ML complex. The emerald-green M(2)L complex exhibits a very low stability which permits the preparation of pure stoichiometric bluish ML complex solutions by percolation of the former through a cation-exchanger in the sodium form. Both complexes exhibit a similar visible spectrum with maxima located at 605 and 655 nm, the maximum absorptivity of M(2)L being slightly greater (e(655) approximately 5.8 x 10(4) 1. mole(-1). cm(-1)) than that of ML (E(655) = 5.0 +/- 0.3 x 10(4)). The complexes have a net negative charge which depends strongly on the particular washing conditions used for the complexes sorbed on chloride-form anion-exchange resins.

New type of blue ternary complex of arsenazo I with plutonium (IV) in the presence of hydrogen peroxide: preliminary investigations.

The preparation and spectrophotometric properties of a new type of complex compound of arsenazo I with Pu(IV) in the presence of H(2)O(2) are described. The new compound has a blue colour, derived from a wide absorption band with a maximum at 610 nm. and a corresponding molar absorptivity of 4 x 10(4) l. mole(-1).cm(-1). From 2 hr after its preparation this curious new compound undergoes for several days a steady decomposition accompanied by decolorization. The formation of similar peroxy Pu(IV) complexes has not so far been shown to take place with arsenazo III or with any other "arsenazo-type" reagent.

Spectrophotometric determination of the protolytic dissociation constants of the new chromogenic reagent "PALLADIAZO"-II Study of the protonation processequals, single dot aboves undergone by the azo-groups of the reagent in sulphuric acid media.

The protonation of the reagent 1,8-dihydroxynaphthalene-3,6-disulphonic-2,7-bis(azophenyl-p-arsonic) acid ("palladiazo") has been investigated by a spectrophotometric method in 0.25-18M sulphuric acid media. Graphical assessment of the experimental results points to the protonation of only one azo-group, although a two-stage protonation process cannot be conclusively ruled out at very high acidity. The first protonation instability constant is pK(9) = -(2.4 +/- 0.1) and the second is tentatively estimated as -7.4. Most of the current views on the complexation and protonation reactions of bis(azophenyl)chromotropic acid derivatives.with metal cations and protons are reviewed and critically discussed in some detail in order to interpret the experimental findings. It is concluded that the fully protonated palladiazo molecule exists in very concentrated acid media predominantly in the form of a symmetrical positively charged tautomeric quinonehydrazone proton complex species which is responsible for the appearance of a very strong single absorption band with a maximum at 665 run which gives the protonated reagent solutions a characteristic deep-emerald-green colour.