Presence Of Bisulfate Research Articles

Effect of Acidity on Ice Nucleation by Inorganic-Organic Mixed Droplets.

Aerosol acidity significantly influences heterogeneous chemical reactions and human health. Additionally, acidity may play a role in cloud formation by modifying the ice nucleation properties of inorganic and organic aerosols. In this work, we combined our well-established ice nucleation technique with Raman microspectroscopy to study ice nucleation in representative inorganic and organic aerosols across a range of pH conditions (pH -0.1 to 5.5). Homogeneous nucleation was observed in systems containing ammonium sulfate, sulfuric acid, and sucrose. In contrast, droplets containing ammonium sulfate mixed with diethyl sebacate, poly(ethylene glycol) 400, and 1,2,6-hexanetriol were found to undergo liquid-liquid phase separation, exhibiting core-shell morphologies with observed initiation of heterogeneous freezing in the cores. Our experimental findings demonstrate that an increased acidity reduces the ice nucleation ability of droplets. Changes in the ratio of bisulfate to sulfate coincided with shifts in ice nucleation temperatures, suggesting that the presence of bisulfate may decrease the ice nucleation efficiency. We also report on how the morphology and viscosity impact ice nucleation properties. This study aims to enhance our fundamental understanding of acidity's effect on ice nucleation ability, providing context for the role of acidity in atmospheric ice cloud formation.

Molecular mirror images, dense ice phases, organic salts at interfaces, and electrochemical deposition: exotic applications of the Pirogov–Sinai theory

The Pirogov–Sinai theory of phase transitions is used to prove the existence of ordered molecular phases at low temperatures in statistical mechanical models for several types of molecular systems. A three-dimensional lattice gas containing two molecular mirror images (enantiomers) was proved to undergo enantiomeric phase separation for one domain of interactions and to contain ordered racemic phases for another domain of interactions. A model for ice VII, which contains disordered hydrogen bonds, was introduced and proved to undergo a transition to a low-temperature phase which has the ordered hydrogen-bonded structure of ice VIII. A lattice gas model for guanidinium nitrate at the mercury–water interface was introduced and proved to form a condensed monolayer with an open, hexagonal hydrogen-bonded structure that agrees with the structure proposed on the basis of experiments. A model for the underpotential deposition of copper on the (111) surface of a gold electrode in the presence of bisulfate was proved to undergo a sequence of voltage-dependent ordered interfacial phases that agree with experiment.

Cluster variation study of the underpotential deposition of Cu on Au(111) in the presence of bisulfate

A cluster variation method is developed to study the phase transitions and the structures of phases which occur at the fluid-crystal interface during the underpotential deposition of a metal on an electrode in the presence of an anion, such as bisulfate. In addition to the possibility of first-order condensation phase transitions occurring during the deposition of a metal, the steric repulsion of adsorbed anions can also cause an order-disorder transition. Using clusters containing six adsorption sites, the method is applied to the underpotential deposition of copper on (111) gold in the presence of bisulfate. In order to fix a constant in the expression for the entropy, the effect of the hard-core exclusion of a pair of first-neighbor bisulfates, in addition to the effect of finite interactions, is calculated exactly in the limit of high temperature. The cluster method yields two coupled adsorption isotherms for copper and bisulfate in terms of their activities and coverages. The resulting isotherms show an order-disorder transition due to the hard-core exclusion of neighboring bisulfate ions, as well as two first-order phase transitions in the copper and bisulfate coverages which correspond to the two spikes in the experimental voltammogram. The cluster method also gives the local structure of the phases which occur as the voltage is changed.

FT-IR Transmission Spectroscopy for Quantitation of Ammonium Bisulfate in Fine-Particulate Matter Collected on Teflon® Filters

A quantitative measurement method for the determination of fine-particle bisulfate in ammonium bisulfate collected from the ambient air onto Teflon® filters is described. Infrared absorbance measurements of the Teflon® filters are made before and after particle collection. Subtraction of the two spectra reveals the absorbance spectrum of the particles. The presence of bisulfate is identified by characteristic and unique spectral features including prominent absorption bands at 1050 and 870 cm−1. The integrated band absorbance at 870 cm−1 is used for quantitation. Wet chemical measurements of sulfate and hydrogen ion in synthetically generated ammonium bisulfate standards are used in calibration. The lower limit of detection for the bisulfate ion is 150 nanomoles. This amount corresponds to the ammonium bisulfate which would be collected from an air volume containing 1.2-microgram/m3 samples for 24 hours at 10.0 L/min. This method provides a specific, nondestructive, direct measurement of ammonium bisulfate. As such, the method has distinct advantages over indirect methods for the determination of bisulfate ion.