Photometric Determination of Small Amounts of Titanium in Perchloric Acid Using Hydrogen Peroxide
Abstract Generated abstract
This paper describes a photometric procedure for determining small amounts of titanium in perchloric acid using hydrogen peroxide as the color-forming reagent. The method is based on formation of a yellow titanium peroxide complex in strongly acidic solution, with phosphoric acid added to mask possible iron interference and absorbance measured at 413 nm against a calibration graph prepared under identical conditions. The authors present an analytical scheme suitable for titanium contents of about 0.0005 percent and higher, and report statistical evaluation of replicate determinations giving a mean value of 1.25 micrograms with a relative error of 12.7 percent.
Full Text
Photometric Determination of Small Amounts of Titanium in Perchloric Acid Using Hydrogen Peroxide
L. G. Skripova, T. A. Chervenčuk, A. N. Pokrovskaya
(Presented by the scientific seminar of the KhTF)
For the photometric determination of small amounts of titanium in various objects, a large number of reagents are known. The most frequently used are hydrogen peroxide, chromotropic acid, and diantipyrylmethane.
Hydrogen peroxide, as a reagent for the determination of titanium, has an important advantage: first, the reaction can be carried out in a strongly acidic medium and, second, ordinary metals, except iron, do not interfere with the determination. The method is simple, economical in time, and uses readily available, inexpensive reagents. The main drawback of this method is its low sensitivity [1].
The sensitivity of methods using chromotropic acid and diantipyrylmethane is considerably higher, about 0.01 μg/ml, but the use of chromotropic acid requires strict buffering of the solution (pH 2.5—3), while diantipyrylmethane reacts with perchloric acid, forming a compound insoluble in water.
Cases are known in which titanium is determined with hydrogen peroxide in various objects where perchloric acid is conveniently used for decomposing the material, and the determination is carried out in the presence of the latter [2].
E. Sandell [1] indicates that in perchloric-acid solutions the intensity of the color of the solution of the resulting complex \([Ti(H_2O_2)]^{2+}\) [3] does not depend on the acid concentration up to 3.5 M.
Matelli and Monti [4] report data showing that perchloric acid up to 10 percent by volume does not affect the determination of titanium with hydrogen peroxide. Therefore, for the determination of small amounts of titanium in perchloric acid, when the titanium content is within the range of \(5 \cdot 10^{-4}\%\) and higher, a method using hydrogen peroxide was employed, based on the formation of a yellow titanium peroxide complex.
Course of analysis. Into a 25-ml volumetric flask, a volume of perchloric acid corresponding to 1—2 g of it is measured with a pipette; 3 drops of concentrated phosphoric acid are added (to bind any iron (3+) that may be present), then 10 ml of a 5% sulfuric-acid solution is added, and the mixture is stirred. Next, 1 ml of a 3% hydrogen peroxide solution is added, the volume is brought to the mark with a 5% sulfuric-acid solution, the contents are mixed thoroughly, and colorimetry is carried out on an FEK-N-57 with light filter No. 2 (413 mμ) in a 50-mm cuvette. The comparison solution is water. A blank experiment must be set up.
Table
| No. | Quantity determined | \(n\) | \(\bar{x}\), µg | \(\pm S_{\bar{x}}\) | \(t_{0.95}\) | \(\varepsilon\) | \(\varepsilon\%\) |
|---|---|---|---|---|---|---|---|
| 1 | Amount of titanium, µg | 14 | 1.25 | 0.076 | 2.16 | 0.16 | 12.7 |
The amount of titanium is found from a calibration graph, which is constructed under the same conditions in which the sample is treated. The experimental data were processed by the method of mathematical statistics, and the results are given in the table.
REFERENCES
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E. Sendel, Colorimetric Methods for the Determination of Traces of Metals. Moscow, 1964.
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A. K. Babko, A. I. Volkova. Conditions for the colorimetric determination of titanium and vanadium in the form of peroxide complexes. Zavod. labor., IX, 5, 518, 1952.
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S. M. Gutman, E. M. Zagorodskaya, Z. A. Vyrapaeva. A rapid method for determining titanium in cast iron and steel. Zavod. labor., IX, issue 1, 101, 1940.
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Metelli, Monti. Spectrophotometric determination of titanium with hydrogen peroxide. Referativnyi zhurnal—Chemistry series, 15, 61052, 1960.