Direct heterometric microtitration of copper with oxine in the presence of other metals

A new heterometric method is presented for a rapid micro-determination of copper with oxine. 1 mg of copper in 20 ml of solution may be determined with an accuracy of 0-I-0 microgram per ml. The solution may contain 95% Me or Al, 98% Zn, Mn, Co. Ni, Cd or Cr and 99-8% Pb. The determination is made at room temperature and takes 10–20 minutes.     

The heterometric micro-determination of copper with quinaldic acid in the presence of foreign metals

1. During the heterometric determination of copper, bivalent cations may be present in solution in large excesses (>95%) and no complexing agents are necessary. In the presence of zinc, excesses of citrate of tartrate must be added. Error: 0—2 %. 2. Excesses of chromium or aluminum (>95%) are without effect. In the presence of an excess of iron (>95%) the determination is made by the addition of tartrate which increases the maximum density value obtained. Error: 0—3%.     

Micro-heterometric determination of molybdic acid with α-benzoin oxime

1 mg of molybdenum as molybdic acid in 20 ml solution can be titrated heterornetrically with a-benzoin oxime in the presence of ~ 99% of most bivalent or tri valent cations as well as in excesses of tungstic or vanadic acids. Error: 0–2%.     

A precise direct heterometric determination of traces of copper with diethyldithiocarbamate in excesses of metals

The most favorable conditions for the heterometric titration of copper with sodium diethyldithiocarbamate and the influence of complexing agents on the titration were investigated.Titrations of copper were carried out in the presence of large excesses (? 99. 5%) of most of the common cations. A method is presented for a precise determination of traces of copper in metals and salts.The titration time was 7–10 minutes. In most titrations the amount of copper present was determined with an error close to zero.     

Copper salicylaldoxime and its use in the heterometric microdeterminatton of copper in the presence of foreign metals

1. The initial precipitation of copper-salicylaldoxime occurs at pH~1.5.Between pH 1.5 and 3.0, the precipitation is incomplete. A complete precipitation occurs in the pH-region of 3–10. Between pH 10.1 and 10.7 the precipitate redissolves At higher pH's a clear solution is obtained. 2. The solubility of copper salicylaldoximate is about ten times greater in 0.01M sulfuric acid (~0.5·10^-4 mol) than in 0.1M acetic acid. 3. In 10 ml of 0.1M acetic acid solution in the presence of ~99% foreign bivalent metals, one mg copper could be determined heterometrically with an error of 1–2%. 4. In the presence of ~95% alumin um or chromium, either citrate or tartrate (0.2M) were used as masking agents. In the presence of iron (~ 95%), clear end-points were obtained only with citrate. One mg of copper could be determined with an error of 0–3%. 5. Whichever pH is used, copper is not precipitated in the presence of ethylenediaminetetraacetate.     

Preconcentration and separation of traces of mercury by reduction of metallic copper and determination by atomic absorption spectrometry without flame]

A micro-column of copper can be used to separate quantitatively as little as 5 ng of mercury from small volumes of solution. For large volumes, e.g. 500 ml, separation depends on the flow rate and on adsorption phenomena; the latter effect can be overcome by addition ofcomplexing agents. The mercury amalgamated on copper is determined directly by non-flame atomic absorption spectrometry. The limit of determination is 1–2 ng. The method is faster and more selective than preconcentration by electrolysis.     

Heterometric micro-determination of uranium (VI) by precipitation with ferrous cyanide

A method is presented fur the determination of uranium (VI) by a heterometric titration with K₄[Fe(CN)₆]. 0.5–3 mg of uranium in 10 ml solution may be determined in 15–20 minutes. The error amounts to 0–3%.     

Heterometric micro-determination of cobalt with α-nitroso-β-naphthol in the presence of foreign metal

A heterometric method is presented for the determination of cobalt in solutions or other metals. The cobalt comprises 0.1–3% of the total metal content. The amount of cobalt determined is 0.2–0.5 mg in 20 ml of solution. The titration generally takes 10–20 minutes at room temperature, and the error is 0–3%.     

A quick and precise heterometric determination of iron with aluminon in excesses of foreign metals

A method is presented for the heterometric determination of 0.2–0.5 mg ferric iron with aluminon. The analysed solution may contain excesses of coloured or colourless foreign bi-or trivalent Cations. The latter may make up ? 99.5% of the total metal content. The working conditions were studied. The determination lasts 10–15 minutes and the error is 0–2%.     

Amperometric titration of copper with tetraethylenepentamine

Tetraethylenepentamine is a very selective titrant for the determination of copper in acidic medium. With amperometric end-point detection as little as 0.1 mg copper in a volume of 25 ml can, be determined with an accuracy of ± 1%. When the titration is performed in acetic acid/ ammonium acetate buffer of pH 4.1, only mercury causes significant interference.     

Coulometric titration of +2 copper with electrogenerated +2 tin

Using a supporting electrolyte composed of 4 M sodium bromide-0.2 N hydrochloric acid- 0.2 M stannic chloride, and a platinum generator cathode, +2 copper can be titrated accurately to the +1 state with electrogenerated +2 tin. With potentiometric end-point detection, quantities of copper from about 1 to 35 mg in a volume of 90 ml are titratable with an error of ± 0.3%. The titration is applicable in the presence of most of the elements that are commonly associated with Copper.     

Determination of traces of antimony and tin in copper by anodic stripping voltammetry

The determination of antimony and tin impurities in copper by anodic stripping voltammetry on a hanging mercury drop electrode is described. Antimony and tin were previously separated from copper by distillation with hydrobromic acid or a mixture of hydrobromic acid and hydrochloric acid. The method was applied to the analysis of various high-purity copper samples, commercially available, showing satisfactory sensitivity and precision. The determination limit was about 1.4· 10^-9M for antimony and 7·10^-10M for tin in solution, for pre-electrolysis times of respectively 15 and 25 min; this corresponds to 0.8 p.p.b. of antimony and 0.3 p.p.b. of tin for a 2-g sample and a final volume of 10 ml after separation.     

Coulometric titration of gold with electrogenerated chloro-cuprous ion

A method for the coulometric titration of +3 gold to the metallic state with clectrolytically generated chloro cuprous ion is described Quantities of gold from as little as I mg to 100 mg or more were titrated in a volume of 100 ml with an average error of ± 0.3%.The titration is applicable to the determination of gold in the presence of large amounts of copper, silver, mercury, lead, and most of the elements with which gold commonly is associated. Small amounts of +4 platinium (less than half the amount of gold) are innocuous, but larger quantities of platinum produce a large positive error     

Coulometric titration of copper(II) with electro-generated chromium(II)

The current efficiency for the electrogeneration of chromium(II) for use as a coulometric titrant was studied for several supporting electrolytes. With a mercury cathode and a 0.1 M chromic sulfate-0.1 M potassium chloride medium, 0.8 to 2.8 mg of copper (II) in 110 ml of solution can be titrated using potentiometric end-point detection.     

Spectrophotometric determination of niobium in steels with 4-(2-pyridylazo)-resorcinol

A direct method is presented for the spectrophotometric determination of niobium with PAR in mild and alloy steels. Interference is caused only by tantalum and large amounts of copper. A compensating solution is used to correct for coloured ions and for the copper-PAR complex. The method covers the range 0–100 mg of niobium, and Beer's law is obeyed from 0 to 2.0μg Nb/ml. A molar absorptivity of 14,400 at 536 nm was found for the niobium-PAR complex, with a relative standard deviation of ±0.6%.     

Determination of sulfur dioxide in air

The determination of sulfur dioxide in air is based on a preliminary purification with a cellulose filter and 80% isopropanol and absorption of sulfur dioxide by means of two midget impingers in 0.3 N hydrogen peroxide. The formed sulfate is titrated in an aliquot with 0.005 M barium perchlorate employing Chlorophosphonazo III (CPA) as an indicator. The method is suitable for 0.3–19.0 mg of sulfur dioxide per 50 liters of air. The standard deviation of the titration is ±0.02 ml per consumption of 5.00 ml and is four times smaller than that of the Thorin method.     

The heterometric microdetermination of mercury of mercaptobenzthiazole

The heterometric determinations of murcury or mercaptobentlnazole are very sensitive reactions. An aqueous or a dilute alcoholic solution is used and the titration may lie carried out at pH 2–10. If meicaptobenzlhiazole is determined, two analytical end-points are obtained : the first gives an estimate, the second gives the precise end-point. In all cases, the insoluble Hg(MBT)₂ is obtained, The presence of larger amounts of strong acids is disadvantageous Large amounts of acetic acid cause distuibances in aqueous solution; dilute alcoholic .solution is therefore used The theoretical end-point is obtained by the intersection of two lines. In acid solution a horizontal maximum density line is obtained at the end ot the reaction, in alkahne solution a maximum point is obtained instead. 1–2 mg mercury or meicaptobenzthiazole may be determined in 20–30 ml solution with an error of 0–3% 'Ihe titration time is 10–20 mniutes     

A quick heterometric microdetermination of calcium as sulfate in excesses of magnesium or other supplements

An alcoholic solution of calcium chloride (2–4 mg Ca) which contains ≧ 95% magnesium as chloride besides other impurities can be titrated directly heterometrically with a standardized alcoholic sulfuric acid solution. The titration lasts about 15 minutes at room temperature. Error 0–2%.     

Rapid titrimetric determination of microgram amounts of fluoride ion with spadns -thorium lake

A rapid titrimetric method has been developed for the determination of microgram amounts of fluoride ion in the range from Img-Ioomg, in 50 ml final volume. It involves the adjustment of pH, addition of 1 ml of 0.02% SPADNS indicator, dilution to volume and titration with standard 0.004M Th(NO₃)₄ until the colour obtained matches a blank containing the buffered solution of the indicator with a. trace of thorium nitrate solution. Interference by various ions was also studied. The method described for the determination of fluoride ion is very rapid and the colour change at the end point being sharp, the detection of the end point is very easy. The method is applicable to pure solutions of fluondes.     

Extraction-photometric determination of uranium(IV) with chlorophosphonazo-III

A sensitive spectrophotometric method has been developed for the determination of uranium. The uranium(IV)-chlorophosphonazo-III complex is extracted into 3-methyl-1-butanol from 1.5–3.0 M hydrochloric acid solution. Maximal absorbance occurs at 673 nm and Beer's law is obeyed over the range of 0–15 μg per 10 ml of the organic phase. The molar absorptivity is 12.1·10⁴ 1 mole^?1 cm^?1. Uranium can be determined in the presence of fluoride. sulfate and phosphate. Nitrate ion and elements (chromium, copper, iron) which affect the reduction of uranium(VI) or stability of uranium(IV) interfere.