Studies on the thermal decomposition of some metal complexes of 5,5′-methylendisalicylhydroxamic acid

The thermal behaviour of the chelates of 5,5′-methylendisalicylhydroxamic acid with Pb(II), Zn(II), Ni(II), Cd(II), Fe(III), Cr(III), Al(III), Ti(IV), V(V), Mo(VI) and Cu(II) has been studied by thermogravimetry (TG), differential thermal analysis (DTA), IR spectroscopy and X-ray diffraction.The compounds decompose through three major steps, dehydration, transformation of the anhydrous hydroxamates to intermediate N-hydroxylactams, which decompose to yield metal oxides as the final products.     

Electrochemical nucleation: Part II. The electrodeposition of silver on vitreous carbon.

A study has been made of the electrochemical nucleation of silver on vitreous carbon from aqueous solutions of silver nitrate.The nucleation is shown to be progressive and mass transferred controlled. The rate of nucleation is somewhat better described bythe atomistic theory than by classical theories. The addition of EDTA reduces the rate of nucleation as the result, it is suggested,of the adsorption of EDTA by the graphite surface. The sensitivity of the rate of the nucleation to the condition of the graphitesurface is also shown by the effects of changing the salvation acidity.     

Analytical applications of picolinealdehyde salicyloylhydrazone: Spectrophotometric determination of nickel and zinc

With a view to the use of picolinealdehyde salicyloylhydrazone as analytical reagent, a study of the physical properties and chemical reactions of this substance has been carried out. It reacts with nickel (λ_max = 375 nm, ? = 3.9 × 10⁴M^?1cm^?1) or zinc (λ_max = 365 nm, ? = 4.8 × 10⁴M^?1cm^?1) to produce a yellow 1:2 complex in both cases. Spectrophotometric determinations of trace amounts of nickel and zinc have been established.     

Determination of manganese(II) by a chemiluminescence reaction

Manganese(II) ( 1.5 ng/ml) is determined by measuring either of the two emission peaks given by alkaline oxidation of luminol. Several other metal ions, which enhance both emission peaks, are masked by cyanide ions.     

Spectrophotometric determination of 2-amino-3H-phenoxazin-3-one as a colouring matter in o-aminophenol

A spectrophotometric method using 0.5M hydrochloric acid in methanol as solvent, has been used for the determination of 2-amino-3H-phenoxazin-3-one [APZ], occurring as a coloured impurity in o-aminophenol [OAP]. This impurity dissolves in the acid medium, giving a stable red solution which complies with Beer's law. The method can be applied to the determination of APZ in technical samples of OAP.     

Contact angles in thin liquid films : III. Interaction forces in Newton black soap films

The interaction parameters of Newton black soap films stabilized by NaDS, as derived from contact angle experiments, have been interpretated in terms of the structure and the interaction forces in the films. From the film thickness and the difference between the surface excess of the salt in the film and at the bulk surface it is concluded that (a) the diffuse double-layer overlap in the film is practically complete; (b) the film only contains absorbed DS⁻ ions and an equal amount of Na⁺ counterions, but no salt; and (c) the double layer at the bulk surface is still partly diffuse. A model for the structure of the NB films is proposed according to which the adsorbed DS⁻ ions with their counterions form a two-dimensional square lattice at each film surface. It is found that the interaction free energy of the NB films can be explained by taking into account the electrostatic interactions between the discrete ions in the two opposing surface lattices. The model of the NB film is qualitatively in agreement with the experimental results of other workers.     

Electrochemical behavior of 1-nitroso-2-naphthol in aqueous solutions: Evaluation of the rate constant for the intervening chemical step in an ece mechanism from stirred-mercury-pool chronoamperometric data

In aqueous solution 1-nitroso-2-naphthol is reduced to 1-amino-2-naphthol by an ECE mechanism. The homogeneous first-order rate constant for the chemical reaction of the intermediate can be evaluated with the aid of current-time data obtained during controlled-potential electrolysis with a stirred mercury-pool working electrode, using the Karp-Meites equation for the dependence of quantity of electricity on time, and is found to be equal to 1.1 ± 0.1₅ s^?1.     

Silmization of stainless-steel frits for use in trace metal analysis by high performance liquid chromatography

A simple method has been developed to minimize the interferences related to the metal parts of an analytical system used for trace metal analysis by HPLC. This is accomplished by blocking the exposed metal surfaces with an organosilane. The effect of the silanized stainless steel frits has been demonstrated by injecting diethyldithiocarbamate into columns with and without high metal surface area components. The coating of the silane is quite stable for routine use.     

The quantitative determination of hydrated calcium sulphates in cement by use of self-generating atmosphere thermogravimetry

A method is described for the quantitative determination of hydrated calcium sulphates in cement by use of self-generating atmosphere thermogravimetry. The method is rapid and precise and can be applied (with a suitably modified sample container) with most thermogravimetric equipment.     

Thermal decomposition of alkali metal perchlorates

The effect of past mechanical history on the subsequent thermal decomposition kinetics of sodium, potassium, rubidium and caesium perchlorates, has been investigated. At low temperatures the decomposition of all these salts is significantly sensitized by pre-compression. At high temperatures, however, prior compression results in a lowered decomposition rate in the case of potassium, rubidium and caesium perchlorates and in an increase in the thermal reactivity of sodium perchlorate. The high temperature behaviour is shown to be an indirect consequence of the low temperature behaviour. The difference in behaviour between sodium perchlorate and the other alkali metal perchlorates is explained on the basis of the stability of the respective chlorates, formed during the low temperature decomposition. This is substantiated by experiments which show that the addition of sodium chlorate to sodium perchlorate brings about a sensitization while potassium perchlorate admixed with potassium chlorate results in a desensitization at high temperatures.     

New spectrophotometric method for the determination of phenolic hormones

A new simple, selective and accurate spectrophotometric method is described for the determination of mono- and dihydric phenolic hormones (oestrogens and catecholamines) by nitration at 50 degrees and 100 degrees , respectively, for 10 min, followed by treatment with alkali. Coloured products with absorption maxima at 430, 385, 430, 380 and 380 nm, linearly proportional to the concentration of oestrone, oestradiol, ethinyloestradiol, adrenaline and noradrenaline, respectively, are obtained. Information is presented on the effect of nitration time, temperature, solvents, and alkali concentration. The method is satisfactorily applied to the determination of these hormones in the range 10-50mug ml in the final solution, of volume 10ml. The relative standard deviation is +/- 0.5% and no interferences are caused by non-phenolic hormones.     

Application of an intensified diode array system to diagnosis of matrix effects and the rapid sequential determination of thiamine and riboflavin with fluorescence detection

The unique capabilities of a multiple wavelength spectrofluorometer based on an intensified diode array detector are used for diagnosis of matrix effects and for rapid sequential determination of two analytes. This system is used to investigate problems due to background fluorescence, blank reactions, and scattering for the determination of thiamine in cereal and urine samples by a fluorometric kinetic procedure. A novel determination of thiamine and riboflavin in vitamin pills is based on monitoring the native fluorescence of riboflavin over one wavelength region, and the rate of formation of fluorescent thiochrome from thiamine over another wavelength region, after a computer-controlled change in the pH of the reaction mixture.     

A new kinetic method for the determination of magnesium and its application to natural waters

A kinetic method is described for the determination of trace amounts of magnesium in the presence of calcium. The procedure is based on the inhibition of the manganese(II) catalyzed aerial oxidation of 1,4-dihydroxyphthalimide dithiosemicarbazone reaction by

2. Effect of Transition Metals^a

Transition metal	Concentration (M)	Percentage inhibition	Mg(II) found (×l05M)
Fe(II)	3.6.10?5	54.1	4.62
Fe(III)	3.6.10?5	47.8	4.48
Co(II)	3.4.10?5	50.0	4.53
Ni(II)	3.4.10?5	50.0	4.53
Cu(II)	3.1.10?5	52.0	4.56
Zn(II)	3.0.10?5	54.1	4.62
Cd(II)	1.7.10?5	52.0	4.56
Hg(II)	9.9.10?6	45.8	4.44
Sn(II)	2.1.10?6	50.0	4.52
Pb(II)	1.2.10?6	54.1	4.62

a

Conditions: 4.53.10^?5M Mg(II), 35 ng Mn ml^?1, 0.429 M ammonia, 1.6.10^?4M OH-PDT.

3. Determination of Magnesium in Natural Waters

			Mg(II) found (M)b
Natural water	Ca(II) presenta		Atomic absorption
sample	M	Kinetic absorption	method
Commercial	3.45 · 10?4	1.65 · 10?3	1.74 · 10?3
Commercial	5.46 · 10?4	1.57 · 10?4	1.81 · 10?4
Untreated	6.13 · 10?4	2.16 · 10?4	2.40 · 10?4
Treated	4.95 · 10?4	1.93 · 10?4	2.17 · 10?4

a

EDTA titration less the magnesium.

b

Average of three separate determinations. traces of magnesium(II). The reaction is followed spectrophotometrically by measuring the rate of change in absorbance at 594 nm. The calibration graph (percentage inhibition vs magnesium concentration) is linear in the range 329–535 · 10^?5M with an accuracy and precision of 1.2%. The method has been applied to the determination of magnesium in natural waters at low concentrations.