Chromium aluminium

Medium acid baths, pH 4-5 At this acidity a dichromate solution plus sulphate ion as activator is sufficient to deposit chromate films in 30 min or so at room temperature or in a few minutes at boiling point. Unfortunately, a solution of alkali dichromate and alkali sulphate is quite unbuffered, and other substances must be added to give the bath a useful life over the working pH range. Acetates have been used successfully, but salts of aluminium, chromium, manganese and zinc have been more commonly employed. The pH of the solution rises slowly during use until basic chromates or sulphates begin to precipitate. The solution can then be rejuvenated by the addition of chromic or sulphuric acid or acid salts. 

Determination of titanium with tannic acid and phenazone Discussion. This method affords a separation from iron, aluminium, chromium, manganese, nickel, cobalt, and zinc, and is applicable in the presence of phosphates and silicates. Small quantities of titanium (2-50 mg) may be readily determined. 

Determination of uranium with cupferron Discussion. Cupferron does not react with uranium(VI), but uranium(IV) is quantitatively precipitated. These facts are utilised in the separation of iron, vanadium, titanium, and zirconium from uranium(VI). After precipitation of these elements in acid solution with cupferron, the uranium in the filtrate is reduced to uranium(IV) by means of a Jones reductor and then precipitated with cupferron (thus separating it from aluminium, chromium, manganese, zinc, and phosphate). Ignition of the uranium(IV) cupferron complex affords U308. 

In the presence of certain cations [sodium, potassium, lithium, calcium, aluminium, chromium, and iron(III)], co-precipitation of the sulphates of these metals occurs, and the results will accordingly be low. This error cannot be entirely avoided except by the removal of the interfering ions. Aluminium, chromium, and iron may be removed by precipitation, and the influence of the other ions, if present, is reduced by considerably diluting the solution and by digesting the precipitate (Section 11.5). It must be pointed out that the general method of re-precipitation, in order to obtain a purer precipitate, cannot be employed, because no simple solvent (other than concentrated sulphuric acid) is available in which the precipitate may be easily dissolved. 

Dusts of magnesium, zirconium, titanium and some magnesium-aluminium alloys [1], and (when heated) of aluminium, chromium and manganese [2], when suspended in carbon dioxide atmospheres are ignitable and explosive, and several bulk metals will bum in the gas. 

Other methods reported for the determination of beryllium include UV-visible spectrophotometry [80,81,83], gas chromatography (GC) [82], flame atomic absorption spectrometry (AAS) [84-88] and graphite furnace (GF) AAS [89-96]. The ligand acetylacetone (acac) reacts with beryllium to form a beryllium-acac complex, and has been extensively used as an extracting reagent of beryllium. Indeed, the solvent extraction of beryllium as the acety-lacetonate complex in the presence of EDTA has been used as a pretreatment method prior to atomic absorption spectrometry [85-87]. Less than 1 p,g of beryllium can be separated from milligram levels of iron, aluminium, chromium, zinc, copper, manganese, silver, selenium, and uranium by this method. See also Sect. 5.74.9. 

G. Ghosh, Aluminium-chromium—copper, in Ternary Alloys A Comprehensive Compendium of Evaluated Constitutional Data and Phase Diagrams, G. Petzow and G. Effenberg, Ed., VCH Publishers, New York, 1992, pp. 311-319. 

Cobalt[III] acetate (see Cobalt and eobalt compounds) Cobalt-aluminium-chromium spinel (see Cobalt and cobalt compounds) Cobalt and cobalt compounds (see also Implants, surgical)... 

Aluminium and magnesium selenides are very similar light brown powders, unstable in air. Zinc and iron (ferrous) selenides are more stable in air, the zinc compound being citron-yellow and the iron compound black and metallic in appearance.8 The latter becomes brown in air owing to oxidation. Ferric selenide is difficult to obtain pure. Cadmium selenide, which is dark brown, is very stable in colour and is used as a pigment. With thallium, selenium is said to form three distinct compounds,9 but analyses of these compounds have led to discordant results. The selenides of aluminium, chromium and uranium cannot be prepared in the wet way. Nickel selenide, unlike the sulphide, shows no tendency to form a colloidal solution. 

The difference between these two amounts (as SO,) is diminished by 014% (referred to leather with the normal amount of moisture), this being the mean quantity of SO, formed, during the determination of the total sulphuric acid, by the oxidation of the sulphur in the hide substance. It scarcely needs mention that, when aluminium, chromium and ferric sulphates are present, these lose sulphuric anhydride during the determination of the combined sulphuric acid and are converted into oxides. To obtain exact results in this case, it is necessary to ignite strongly to complete decomposition of these sulphates, to estimate the three oxides in the ash and to subtract from the resultant free sulphuric add also the SO, corresponding with the oxides thus found. 

The preparation of lyophilic sols is easy and most of the time a mixture of the dispersion medium and the substance to be dispersed need only be stirred. Gelatine, for example, disperses almost spontaneously in water. The hydroxides of iron, aluminium, chromium and zirconium as well as vanadium pentoxide and silicic acids all belong to the group of hydrophilic colloids. 

Copper, Zinc, Manganese Aluminium, Chromium, Vegetable oils Flame AAS [91]... 

Aliquots of the digest are analysed for aluminium, chromium, iron copper and zinc by direct flame AAS. Together with the samples, blanks and standards covering the range from 0.1 to 30 pg/ml of each of the above metals in 10% sulfuric acid were also run. 

Sulphides of boron, aluminium, chromium, and silicon are at once decomposed by water, and cannot, therefore, be produced in aqueous solution. They are white substances formed by heating the elements to a high temperature in a current of sulphur vapour. 

All other sulphates are soluble in water, and can therefore be prepared by one of the usual methods, such as treatment of the oxide, carbonate, or metal with the acid. Dilute sulphuric acid dissolves magnesium, zinc, cadmium, aluminium, chromium, iron, manganese, nickel, and cobalt other metals resist its attack, because their electroaffinity is less than that of hydrogen. The order is Cs, Rb, K, Na, Li, Ba, Sr, Ca, Mg, Al, Mn, Zn, Cd, Cr, F e, Co, Ni, Pb —H Cu, Hg, Ag, Pt c., Au. All the metals to the left of hydrogen in the table are attacked, because they receive their ionic charge from the hydrogen... 

Belcher, R., Jenkins, C. R., Stephen, W. I., Uden, P. C. Preparative gas chromatography of volatile metal compounds. I. Separation of aluminium, chromium and iron (3-diketonates. Talanta 17, 455 (1970). 

Gas chromatography has also been applied to the determination of various other cations in non saline waters including aluminium, chromium, cobalt, mercury and silicon. 

P. Vinas, N. Campillo, I. Lopez-Garcia, M. Hemandez-Cordoba, Electrothermal atomic absorption spectrometric determination of molybdenum, aluminium, chromium and manganese in milk, Anal. Chim. Acta, 356 (1997), 267-276. 

Iridium sulphate unites with the sulphates of the alkali metals to yield a series of well-defined crystalline salts known as alums. These are isomorphous with the better known alums of aluminium, chromium, and iron. Application of Mitscherlich s Law, therefore, points to their having a composition represented by the general formula ... 

The sulphides of aluminium, chromium, and magnesium can only be prepared in the dry, as they are completely hydrolysed by water ... 

If a phosphate was present, the precipitate obtained on addition of ammonium chloride and hydroxide may contain phosphates of such metals as calcium, etc., which are normally precipitated in later groups in systematic analysis. The precipitate is therefore dissolved in dilute hydrochloric acid, and the solution nearly neutralised with sodium carbonate. Sodium acetate is now added, and the whole boiled. The precipitate contains the phosphates of aluminium, chromium, and iron, and is treated, as already indicated, with sodium peroxide and water. 

Cupferron or amino nitroso phenyl hydroxylamine 1 may be used for the direct precipitation of iron in acid solution, in the presence of aluminium, chromium, cobalt, nickel, and zinc. Copper is precipitated along with the iron, but is easily removed afterwards by treatment with ammonia, m which it is soluble. 

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