David N. Hume

A sampler for the in situ collection of marine sedimentary pore waters

Abstract An in situ sampler for pore waters of marine sediments is described. Filtered pore water from six depths in the upper 2 m of sediment and bottom water are collected and stored in capillary tubing, thereby preserving sampling sequence. Tests demonstrate the collection of uncontaminated samples.

In situ Sampler for Marine Sedimentary Pore Waters: Evidence for Potassium Depletion and Calcium Enrichment

A device for sampling the interstitial waters of deep-sea sediments in situ has been developed and tested. The sampler collects a series of samples over a depth of 1.5 meters in the sediment and thus makes possible the accurate delineation of chemical gradients existing in the pore waters. Samples collected in the North Atlantic indicate that significant gradients of K+ and Ca2+ exist in the sediments sampled. Interstitial solutions sampled between Ireland and Cape Cod, Massachusetts, are characterized by the depletion of K+ and the enrichment of Ca2+.

Direct determination of bismuth and antimony in sea water by anodic stripping voltammetry

A method based on anodic stripping voltammetry at the mercury-coated graphite electrode has been developed for the direct determination of bismuth and antimony at their natural levels in sea water. Bismuth plated at -0.4 V from sea water made 1 M in hydrochloric acid gives a stripping peak proportional to concentration at -0.2 V without interference from antimony or other metals normally present. Antimony may be plated from sea water made 4 M in hydrochloric acid and gives a stripping peak at -0.2 V proportional to the sum of bismuth and antimony. By use of the standard addition technique, satisfactory results were obtained for sea water samples with concentration ranges of 0.02–0.09 μg kg−1 for bismuth and 0.2–0.5 μg kg−1 for antimony.

Stability constants of mononuclear fluoborate complexes in aqueous solution

Abstract Equilibrium concentrations of fluoride and hydroxide ions in aqueous boric-acid-sodium fluoride mixtures have been determined using specific ion electrodes. Stability constants have been calculated for the fluoborate complexes formed as the first fluoride ion is added and as the subsequent three replace hydroxide ions on the boron central atom in a medium of 1·M sodium nitrate at 25° and at 35°C. The values found for log β n , equilibrium constants for the reaction B(OH) 3 + n F − = BF n (OH) 4− n − + ( n −1) OH − 1 ⩽ n ⩽ 4 are -0·30±0·06 ( n = 1); -6·27±0·01 ( n =2); -14·23±0·01 ( n =3) and -12·62±0·01 ( n =4) at 25·C. The corresponding values at 35°C are -0·27±0·06, −6·2±0·1,

Environmental mercury: rapid determination in water at nanogram levels.

Mercury compounds and free mercury are determined by emission spectrophotometry in a radiofrequency helium plasma. The method is simple, rapid, directly applicable to environmental water samples, and subject to few interferences. The useful working range is 10 nanograms to 10 micrograms, or 1 part per billion to 1 part per million in 10 milliliters of sample. The limit of detection is about 2 nanograms.

Determination of amides.

Abstract A method has been developed for the quantitative determination of amides. The compound is saponified with a large excess of alkali and the resulting solution passed through a heated cationexchange resin in the hydrogen form. The resin neutralizes the excess sodium hydroxide and converts the carboxylic salt to the free acid which is then titrated directly in the effluent with standard alkaline solution. The time required for a determination is less than one hour.

Ozone as Releasing Agent: The Determination of Trace Mercury in Organic Matrices by Cold Vapor Atomic Absorption

Abstract Ozonization of aqueous solutions of organomercurials and mercury salts in organic complexing agents is recommended for releasing the mercury for direct determination by cold vapor atomic absorption. The combination of ozonization and subsequent reduction by sodium borohydride is particularly effective.

DETERMINATION OF BARIUM AND STRONTIUM IN SEA WATER.

Abstract A process based on ion-exchange concentration and separation followed by flame photometry has been developed for the determination of strontium and barium at natural levels in sea water. These elements are stripped from 1-I samples of sea water by means of a cation-exchange resin in the calcium form and selectively eluted with CyDTA and EDTA respectively. Factors influencing the intensity of strontium and barium in hydrogen flames have been studied. The standard deviations of the method are 0.05 p.p.m. for strontium and 0.6 p.p.b. for barium and the accuracy of the method is more than sufficient to demonstrate clearly the variability of Sr/Cl and Ba/Cl ratios with depth and location

Thermometric titrations in acetonitrile

Abstract The use of acetonitrile as a medium for thermometric acid-base titrations has been studied. Satisfactory titrations are obtainable for a wide variety of amines and organic acids, but the instability of the solvent in the presence of strong bases greatly limits its practical applicability. Data are given on the heats of neutralisation of various acids in acetonitrile, and the results for m - and p -substituted benzoic acids are shown to correlate well with their Hammett σ-values.

AMPEROMETRIC TITRATION OF CERIUM(III) WITH FERRICYANIDE

Abstract Milligram and larger quantities of cerous cerium may be determined accurately and precisely, even in the presence of large amounts of ceric salts, by amperometric titration in 3 to 4M potassium carbonate solution with potassium ferricyanide. A rotating platinum microelectrode held at the potential of the saturated calomel electrode is recommended.