Solubility of lead sulfate in solutions of sulfuric acid, determined by dithizone with a photronic cell

Abstract

New determinations of the solubility of lead sulfate in sulfuric acid solutions have been made, using diphenylthiocarbazone, commonly called dithizone, as the r eagent. This provides a very sensitive method for small quantities of lead. The eq uivalence point was detected by a simple arrangement of a photronic cell and color filter. The range of concentrations of acid extended from 0.1 to 50 percent H 2S04• Determinations of the lead could be made with an average error not exceeding 0.7 microgram (,..g). Determinations were made at 25° and 0° C, employing solutions, some of which were brought to saturation equilibriu m from undersaturation and others from supersaturation. Important maxima and minima in the solubility curves which had not been reported previously were found. Tables are given for the solubility of the salt at 25° and 0° C. Comp arison is made of the effect of H 2S0 4 on the solubility of lead and mercurous sulfates. The trend of the curves for these is strikingly similar, although the latter is more than 80 times as soluble. CONTENTS Page

In Situ Transmission X-Ray Microscopy of the Lead Sulfate Film Formation on Lead in Sulfuric Acid

“…This equation assumes that all the PbSO 4 products remained on the surface, which is a reasonable assumption due to the low solubility of PbSO 4 in H 2 SO 4 . 41 Once the change in the quantity of charge (Q) was determined using Eq. 6, i corr was calculated from the first order derivative of the quantity of charge with respect to time: ) unless CC License in place (see abstract …”

The application of DPASV to the determination of the low temperature solubility of lead sulphate in sulphuric acid solutions

“…2 (8), are also shown for comparison. At temperatures of 0 to -40°C (broken line) there is very little correlation (correlation coefficient = -0.26) between the solubilities (determined at CPRC) and temperature.…”

“…The previous methods cited were not sufficiently sensitive to determine lead quantitatively at concentrations much less than 1 ppm, whereas at -50°C, concentrations of the order of 40 ppb might be expected on the basis of extrapolation of the van't Hoff expression, using the Craig and Vinal data (8). However, measurement of such low concentrations of lead are well within the capability of modern analytical techniques such as atomic absorption spectroscopy (AA) and stripping voltammetry and both methods were assessed for the present work.…”

“…Lead sulphate solubilities have been determined as a function of sulphuric acid concentratioils in the temperature range of 0 to $50°C (8)(9)(10)(11)(12)(13)(14).…”

“…A method based on the reaction of dissolved lead with dithizone to form a coloured complex which could be detected photometrically (8,9) gave good agreement with iodometric determination of lead, following evaporative concentration of dissolved lead chromate (10). Other methods (11)(12)(13)) also agreed well, except for the lead chromate-colorimetric method of Crockford and Brawley (14), where competition between chromate and sulphate ion pairing may be the cause of the low values in the range of 0.5-50x acid.…”