THE DETERMINATION OF SMALL AMOUNTS OF FLUORINE IN WATER

1940 ◽  
Vol 18b (6) ◽  
pp. 151-159 ◽  
Author(s):  
Osman James Walker ◽  
Gordon Roy Finlay
Keyword(s):  
Sulphuric Acid ◽  
Perchloric Acid ◽  
Colorimetric Method ◽  
Fluorine Content ◽  
Sodium Ions ◽  
Ferric Ions ◽  
Titration Method

In the survey of Alberta waters in which fluorine content is compared with the prevalence of mottled teeth, the titration method and the colorimetric method for determining fluorine have not always given comparable results. Good results with the titration method are obtained when distillation is carried out with perchloric acid instead of with sulphuric acid. It was found that the colorimetric method is affected by more than 2 p.p.m. of phosphate, aluminium, or ferric ions, and by over 120 p.p.m. of sulphate ions. Moderate amounts of manganous, ferrous, silicate, chloride, and sodium ions do not interfere. When the water contains over 2 p.p.m. of phosphate, aluminium, or ferric ions, or if the water is coloured, the titration method is used. A scheme for correcting for sulphate ions is proposed. The titration method and the colorimetric method used in this laboratory for determining fluorine in waters are given in detail.

Determination of nitrate in sea water by cadmium-copper reduction to nitrite

1967 ◽  
Vol 47 (1) ◽  
pp. 23-31 ◽  
Author(s):  
E. D. Wood ◽  
F. A. J. Armstrong ◽  
F. A. Richards
Keyword(s):  
Standard Deviation ◽  
Sulphuric Acid ◽  
Sea Water ◽  
Colorimetric Method ◽  
Zinc Powder ◽  
Small Samples ◽  
Nitrosyl Chloride ◽  
Sensitivity Limit ◽  
High Concentrations

An accurate, dependable determination of 0–60 μg-at./l. of NO−3-N in sea water has been developed. The sample is treated with tetrasodium ethylenediaminetetraacetate solution and passed through a column of copperized cadmium filings. A nearly quantitative reduction of nitrate to nitrite results. Nitrite is then determined by a diazotization method. Neither sulphide nor high nitrite concentrations interferes. Approximately eight samples per hour per column can be analysed with a standard deviation of 0.12 μg-at./l. at the 20 μg-at./l. level.IntroductionAccurate determinations of nitrate ions in sea water have been difficult, especially under shipboard conditions.The colorimetric method described by Harvey (1926, 1930) and improved by Cooper (1932), Zwicker & Robinson (1944), and others uses strychnidine in concentrated sulphuric acid to produce a red colour. The reagent lacks reliable sensitivity, because it is dependent on the rates of mixing and cooling.In a method by Armstrong (1963), the absorbance of nitrosyl chloride in the UV region is measured with a spectrophotometer. While the method is good for small samples containing high concentrations of nitrate, the use of concentrated sulphuric acid and lack of sensitivity limit its use in routine analysis.A method in which nitrate is quantitatively reduced to nitrite would be advantageous, because nitrite can be readily determined by the sensitive diazotization method proposed by Griess (1879). Several such methods have been proposed. FØyn (1951), Vatova (1956), and Chow & Johnstone (1962) used zinc powder for the reduction, but the reduction is sensitive to temperature, and it is necessary to centrifuge or filter each sample.

scholarly journals The determination of silicate in sea water

1951 ◽  
Vol 30 (1) ◽  
pp. 149-160 ◽  
Author(s):  
F. A. J. Armstrong
Keyword(s):  
Sulphuric Acid ◽  
Sea Water ◽  
Picric Acid ◽  
Colorimetric Method ◽  
Ammonium Molybdate ◽  
Potassium Chromate ◽  
Distilled Water ◽  
Yellow Colour ◽  
Standard Solutions

Silicon in sea water may be present in suspension, in particles of clay or sand, as a constituent of diatoms, etc., or in solution. Some silicon in solution occurs in the form of silicate. This is usually estimated by the colorimetric method of Diénert & Wandenbulcke (1923), which makes use of the yellow colour of the silicomolybdic acid which is formed when ammonium molybdate and sulphuric acid are added to the water (Atkins, 1923). The colour may be compared with that of standard solutions of picric acid (Diénert & Wandenbulcke, 1923) or potassium chromate (Swank & Mellon, 1934). The method is simple but the colour in sea water is often faint and is not easy to match visually, nor is its intensity strictly proportional to the concentration of silicate. Less colour is produced in sea water than in standard solutions made with distilled water and this ‘salt error’ must be allowed for (Brujewicz & Blinov, 1933; Wattenberg, 1937; Robinson & Spoor, 1936).

Determination of Phosphorus in Fruits and Fruit Products by a Spectrophotometry Molybdovanadate Method and by the Official Gravimetric Quinoline Molybdate Fertilizer Method

1969 ◽  
Vol 52 (4) ◽  
pp. 865-870
Author(s):  
Ben Estrin ◽  
Wallace S Brammell
Keyword(s):  
Nitric Acid ◽  
Perchloric Acid ◽  
Colorimetric Method ◽  
Volumetric Method ◽  
Dry Ashing ◽  
Ash Weight ◽  
Molybdate Method ◽  
Phosphorus Determination ◽  
Good Agreement

Abstract A newly developed spectrophotometric molybdovanadate method and the official gravimetric quinoline molybdate fertilizer method, 2.025(b), slightly modified, were used to determine phosphorus in fruits and fruit products. In the former method, the use of hazardous perchloric acid is avoided by dry-ashing the sample as in method 20.017 and by using nitric acid rather than perchloric acid in the molybdovanadate reagent. In the quinoline molybdate method, the sample is dry-ashed in the same way. In both proposed methods, the official ash solution is used for the phosphorus determination as in the official volumetric method, 20.031–20.032. Ash weight can be obtained before preparing this solution; in the official colorimetric method, however, a second aliquot must be dry-ashed for the ash weight. The two proposed methods gave results in good agreement with those obtained by the official volumetric method. These methods are simpler and faster than the two present official methods.

The Spectrophotometry of Sodium Nitrite Solutions in Aqueous Sulphuric and Perchloric Acids and the Equilibrium between Nitrosonium Ion and Nitrous Acid

1963 ◽  
Vol 16 (6) ◽  
pp. 933 ◽  
Author(s):  
NS Bayliss ◽  
R Dingle ◽  
DW Watts ◽  
RJ Wilkie
Keyword(s):  
Aqueous Solutions ◽  
Sulphuric Acid ◽  
Sodium Nitrite ◽  
Perchloric Acid ◽  
Nitrous Acid ◽  
Experimental Error ◽  
Equilibrium Constants ◽  
Solvent Systems ◽  
Nitrosonium Ion

The spectra of solutions of sodium nitrite in aqueous solutions of sulphuric and perchloric acids have been measured at a number of temperatures, and from these spectra the concentrations of the species HNO2 and NO+ have been calculated over the acid-concentration ranges 0-100% sulphuric acid (by wt.) and 0-72% perchloric acid (by wt.). The changes due to temperature were found to be less than the experimental error in the determination of the concentrations of nitrous acid and nitrosonium ion. The equilibria of importance in such systems are discussed and equilibrium constants have been calculated for the reactions H2SO4 + HNO2 <=> H2O + NO+ + HSO4- and HClO4 + HNO2 H2O + NO+ + ClO4- Attempts have been made to correlate the determined values for the concentration of nitrous acid and nitrosonium ion with the acidity functions J0, C0, and Hr for both solvent systems. The nitroacidium ion (H2NO2+) in these systems is found to be less important than previously thought.'

Collaborative Study of Nonaqueous Titration Method for Dodine in Formulations

1969 ◽  
Vol 52 (6) ◽  
pp. 1292-1294
Author(s):  
N Robert Pasarela
Keyword(s):  
Acetic Acid ◽  
Acetic Anhydride ◽  
Perchloric Acid ◽  
Collaborative Study ◽  
Titration Method ◽  
Powder Formulation ◽  
Coefficients Of Variation ◽  
Wettable Powder ◽  
Metanil Yellow

Abstract A nonaqueous titration method for the determination of dodine in 65% wettable powder formulations was studied by ten collaborators. The dodine is extracted from the formulation with acetic acid-acetic anhydride (10 + 90). The extract is filtered, and the resultant acetylated compound in solution is basic enough to be titratable with perchloric acid at a relatively low potential. The titration is carried out potentiometrically or visually, using metanil yellow as an indicator. The coefficients of variation for re-dodecylguanidine acetate standard and the 65% wettable powder formulation were 0.24 and 0.55%, respectively. The method is recommended for adoption as official first action.

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