Spectrophotometric determination of traces of phosphorus by an extraction method

A general method is presented for the spectrophotometric determination of phosphorus at trace levels. It involves extraction of the yellow molybdophosphoric acid with isobutyl acetate and subsequent reduction to heteropoly blue. The method covers the range 0.2–20 μg of phosphorus. A comprehensive study of interferences using standard additions of 10 and 20 μg of phosphorus was carried out and modifications are described to permit the determination of phosphorus in a wide variety of metals and salts.     

丁基罗丹明 B-铋钼杂多酸光度法测定铋

在硫酸介质及吐温存在下，丁基罗丹明Ｂ（ＢＲＢ）与铋钼杂多酸形成离子缔合物，缔合物的最大吸收波长位于６０６ｎｍ，表观摩尔吸光系数为１．７＊１０＾６Ｌ．同，铋质量浓度在０－０．２４μｇ／ｍＬ范围内服从比尔定律。缔合物至少稳定２４ｈ，其摩尔比为ｎ（Ｂｉ）：ｎ（Ｍｏ）：ｎ（ＢＲＢ）＝１：１２：４。考察了２０余种共存离子的影响，大多数常见元素不干扰。本法已用于矿样，合金中铋的测定。     

Spectrophotometric determination of traces of selenium with diaminobenzidine

Diaminobenzidine is suitable for the spectrophotometric determination of traces of selenium. The reaction is very sensitive, the molecular extinction coefficient being as high as 10,200. The reaction is specific, the most common ions causing no perturbation. The procedure is especially valuable for the determination of traces selenium in tellurium and in sulfur, provided that the latter is present in the sulfate form.     

Spectrophotometric determination of traces of arsenic

Arsenic(III) is extracted into carbon tetrachloride from 3.5M sulphuric acid that is 0.8M in potassium iodide. 8-Mercaptoquinoline and acetone are added to the organic extract and the absorbance of the arsenic(III)-8-mercaptoquinolinate formed is measured at 380 nm. Repeating the extraction procedure highly increases the selectivity of the method; only tin(II) interferes with the determination.     

Spectrophotometric determination of traces of antimony

Antimony(III) is extracted into carbon tetrachloride from 4M sulphuric acid that is 0.05M in potassium iodide. 8-Mercaptoquinoline and acetone are added to the organic extract and the absorbance of the complex formed is measured at 390 nm. Repeating the extraction procedure greatly increases the selectivity of the method.     

Spectrophotometric determination of traces of formaldehyde

Summary A comparative study of various colorimetric methods for determining and detecting traces of formaldehyde has been made. Chromotropic acid and 2,7-duiydroxynaphthalene were found to be the best reagents and were subjected to a thorough study. Precise and accurate methods for determining formaldehyde using either chromotropic acid or 2,7-dihydroxynaphthalene are described. The color system produced by following the standard procedure obeys Beer's law. Using chromotropic acid 0.05 g to 2.0 g of formaldehyde per ml can be determined quite accurately. Acrolein seems to be the only seriously interfering substance, and its interference can be much diminished by slightly modifying the standard procedure. The reagent solutions are perfectly stable.     

Spectrophotometric determination of traces of palladium after coprecipitation with tellurium

A spectrophotometric method for the determination of microgram amounts of palladium in the présence of much iron, copper, nickel, cobalt and other common elements (~ 0.5 g) is described. Palladium is separated by stannous chloride precipitation with tellurium as collector. p-Nitroso-diphenylamine is used as the colorimetric reagent, and diethyl oxalate as extradant for the palladium complex (sensitivity = 0.0015 μg $\text{Pd}\text{cm}{}^2$ ≡ log {I₀/I} = 0.001). Silver, selenium and tungsten lead to low results and should not exceed ~ 0.1 mg. The weight ratio Au/Pd should not exceed 10, else results for palladium are high. For Pd > 1 μg, recoveries average 90% or. better.     

Spectrophotometric determination of traces of nitrite with rhodamine 6 G

A simple and highly selective spectrophotometric method is described for the determination of nitrite. The method is based on the measurement of decrease in absorbance at 525 nm of rhodamine 6 G in sulphuric acid medium. The decrease in absorbance is instantaneous on addition of nitrite and remains stable for 2 h. Linear calibration graph passing through the origin was obtained in the range 0.01–0.6 g/ml nitrite. The method is free from interference of Cu²⁺, Fe³⁺ and SO ₃ ^2– which normally interfere in other procedures. The method was applied successfully to the determination of nitrite in well and sea water samples and in KNO₃, NaNO₃, table salt, sugar and milk powder samples.     

金钨杂多酸-丁基罗丹明B光度法测定痕量金

研究了金钨杂多酸（ＡｕＷ）－丁基罗丹明Ｂ（ＢＲＢ）－聚乙烯醇（ＰＶＡ）体系的显色反应．离子缔合物的最大吸收位于５６５ｎｍ，表现摩尔吸光系数ε值为２．９６×１０７ｄｍ３·ｍｏｌ－１·ｃｍ－１，金量在０～２．８μｇ／Ｌ范围内服从比耳定律，检出限为０．１２μｇ／Ｌ（ｎ＝１２），对２．４μｇＡｕ（Ⅲ）／Ｌ测定的相对标准偏差为１．９％（ｎ＝１１）．离子缔合物至少稳定２４０ｈ．研究了离子缔合物的红外光谱，考察了４０多种共存离子的影响，大多数常见离子不干扰，允许２００倍量Ｐｔ（ＩＶ）、４００倍量Ｐｄ（Ⅱ）存在．本法用于某些矿物和炭粉中金的测定，结果与ＡＡＳ法吻合     

Spectrophotometric determination of traces of oxygen in water

Winkler's method of determining oxygen in water by titration of the iodine can not be applied with concentrations below 0.03 mg O₂/litre. We studied the spectrophotometric determination of the iodine-starch complex described by bairstow, francis, and wyatt and succeeded in improving its stability by the addition of potassium sulphate. The intensity of the blue colour is very sensitive to variation of temperature. Below 10° C this influence can be neglected. Upwards from 30° C the intensity rapidly decreases. Instead of performing the determination at 10° C we plotted the extinction coefficient of dilute solutions as a function of the iodine concentration for temperatures ranging from 10 to 30° C. With “the aid of this graph the iodine concentration can be found when the extinction coefficient and the temperature of a solution are determined.With this method we can determine oxygen in water in concentrations ranging from 0.005 to 0.4 mg O₂/litre. Duplicates (for water with a low content of oxygen) differ not more than 0.002 mg O2/litre.