Kinetics and chemical equilibrium of the hydration of formaldehyde

Abstract

Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. AbstractThe reaction rate of the hydration of formaldehyde is obtained from the measured, chemically enhanced absorption rate of formaldehyde gas into water in a stirred cell with a plane gas-liquid interface, and mathematically modelling of the transfer processes. Experiments were performed at the conditions prevailing in industrial formaldehyde absorbers, i.e. at temperatures of 293-333 K and at pH values between 5 and 7. The observed rate constants could be correlated as k h = 2:04 × 105 × e −2936=T s −1 . Using the results, and the dehydration reaction rate constant, obtained previously at similar conditions, the chemical equilibrium constant for the hydration is obtained as K h =e 3769=T −5:494 .

Chemistry of riming: the retention of organic and inorganic atmospheric trace constituents

“…Also, its intrinsic Henry's law constant is low, comparable to sulfur dioxide or hydrochloric acid. However, it undergoes hydration in aqueous solutions forming methanediol (see Reaction R1) with a hydration constant of K hyd = k R1 /k −R1 = 1280 (at T = 298 K; Winkelman et al, 2002).…”

“…This indicates that the retention cannot be fully explained by the value of H * , which only accounts for equilibrium conditions and gives no information on kinetic aspects. If formaldehyde gets dissolved in water its equilibrium between monomeric formaldehyde and methanediol is attained comparatively fast with a rate constant of k R1 = 10.7 s −1 (at T = 298 K, Winkelman et al, 2002). However, if the equilibrium is shifted towards monomeric formaldehyde and, thus, the gas phase, methanediol first has to dehydrate with a very low rate constant (k −R1 = 8.4 × 10 −3 s −1 at 298 K; Winkelman et al, 2000).…”

“…8 Calculated from (Seinfeld and Pandis, 2016) unless specified otherwise. Values for k f and kr from Warneck and Williams (2012); Winkelman et al (2000Winkelman et al ( , 2002; Kanzaki et al (2014); Sano and Yasunaga (1973); Eigen et al (1964). k f and kr specify the forward and reverse reaction rate constants of dissociation/association.…”

Health hazard evaluation report: HETA-2011-0014-3147, formaldehyde exposures during Brazilian Blowout hair smoothing treatment at a hair salon - Ohio.

“…However, formaldehyde when dissolved in water forms a diol called methylene glycol or methane diol, which has a different CAS number of 463-57-0. Formaldehyde gas and the methylene glycol solution exist in a dynamic and reversible equilibrium, and therefore, the aqueous solution is capable of releasing formaldehyde gas [Winkelman et al 2002;Oregon OSHA 2010a;Consumer Federation of American 2011]. An Oregon OSHA report concluded that for the purposes of worker protection it is appropriate to refer to both the hydrated and the non-hydrated formaldehyde as formaldehyde [Oregon OSHA 2010a].…”

Active monitoring of formaldehyde diffusion into histological tissues with digital acoustic interferometry

“…The cold step suppresses enzymatic actions associated with analyte degradation while simultaneously facilitating diffusion of formaldehyde throughout the tissue, and the ensuing warm step rapidly forms formaldehyde linkages to complete the fixation process. 12,13 Because sparse cross-linking takes place at cold temperatures, this method absolutely requires sufficient concentrations of formaldehyde to have diffused into the tissue so that the subsequent warm step does not simply heat tissue in the absence of fixative. This preservation method was shown to preserve protein epitopes with notorious preanalytical sensitivity, such as phosphorylated protein kinase B (pAKT) and phosphorylated epidermal growth factor receptor, which are not currently clinically evaluated but are known to be key biomarkers associated with several forms of cancer.…”