Titanium photometric determination

Extraction-photometric determination of titanium in alloys using naphthalene-2-sulfonic acid and diantipyrylmethane was investigated [3]. No interference from large quantities of many common metals was reported. 

The small quantities of titanium in water samples are concentrated by precipitation on iron hydroxide as carrier. Photometric determination is carried out with the aid of chromotropic acid, which forms a red chelate with titanium (IV) at pH 2 (8 approximately 17,000 at A = 70 nm). 

In these investigations it was also shown that the Kjeldahl process is suitable for the determination of nitrogen in titanium, both in its conventional form - dissolution in hydrofluoric acid, conventional distillation and photometric determination - if certain experimental conditions are observed, and in the modified form of pressure digestion, micro-Kjeldahl process, circulatory distillation and coulometric determination. These results can also be applied to the analysis of titanium alloys. 

Macro quantities of selenium can be determined gravimetrically after reduction to the elemental form by various reagents such as tin (II) chloride, potassium iodide, or ascorbic acid (I). Ooba described a technique whereby the element is precipitated from perchloric acid solution with hydrazine (2). Selenium may be titrated with standard solutions of sodium thiosulfate, iodide, and ferrous, chromous, or trivalent titanium salts after oxidation to Se(VI) (I). Photometric and fluorometric methods based on formation of the piaselenol with diaminobenzidine or 2,3-diaminonaphthalene has been used for the determination of selenium (I, 3,4,5). Interfering elements such as As, Co, Cr, Cu, Fe, Hg, and Ni, are masked with EDTA or other chelating agents. 

The development of photometric methods for the determination of boron in zirconium has to be seen in close relation to that of appropriate methods for the determination of boron in titanium. Therefore reference is also made to some methods developed for the analysis of boron in titanium, with the restriction however that only these studies will be considered which can be applied at the very low boron concentrations of interest here. 

The first carbon determinations in titanium were based on a known method of steel analysis (11), namely the photometric measurement of the yellow colour resulting from the decomposition of carbides with nitric acid. The procedure is as follows a 1 g sample is dissolved in 20 ml sulphuric (1+3) and 10 ml fluoroboric acid (prepared by addition of 130 g boric acid to 280 ml hydrofluoric acid (48 %) under ice cooling) under gentle heating. After dissolution, 5 ml nitric acid (1+1) is added and the solution is filtered into a 50 ml calibrated flask and analyzed by photometry at 450 nm. The colour is stable for 3 hrs. Impurities present in technical titanium do not interfer. 

The conventional variant of the Kjeldahl method to determine nitrogen in zirconium (and titanium) is analysis on a macro scale, as described in various manuals of metal analysis. The ammonia distilled off is usually determined photometrically because only small quantities are likely to be present. Usually the yellow colour produced with Nessler s reagent (8) or the blue colour formed with indophenol (9) are measured. If carried out correctly both variants are of equal merit. 

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