The Low Temperature Heat Capacity and Entropy of Sulfuric Acid Hemihexahydrate. Some Observations on Sulfuric Acid “Octahydrate”<sup>1</sup>

Hornung, E. W.; Brackett, Thomas E.; Giauque, W. F.

doi:10.1021/ja01603a009

Cited by 29 publications

(21 citation statements)

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“…Thus, the larger thermal transition at 200.4 K must correspond to the melting of SAO, and the minor transition at 199.4 K corresponds to the eutectic melting of SAT below ∼37 wt % or ice above ∼37 wt % in contact with each other. This assignment also agrees with Hornung et al 8 who calculated the SAT/ice eutectic to be 198.6 K. The most recent DSC work on this system did not discern between these two transitions but rather interpreted a single transition at 200 K in 20 and 50 wt % samples to be the conversion of octahydrate with either ice (20 wt %) or SAT (50 wt %) into hemihexahydrate. 23 Most likely their instrument did not have the sensitivity to observe the small thermal signal due to melting of ice or SAT at the ice/SAT eutectic.…”

Section: Resultssupporting

confidence: 89%

The Search for Sulfuric Acid Octahydrate: Experimental Evidence

2003

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We have investigated the H 2 SO 4 /H 2 O binary liquid/solid phase diagram using a highly sensitive differential scanning calorimeter (DSC) and infrared spectroscopy of thin films. In particular we have sought to investigate the region from pure ice to sulfuric acid tetrahydrate (SAT), including a detailed look at the sulfuric acid octahydrate (SAO). Our studies have found that there is a unique, repeatable IR spectrum for SAO. Our spectrum is not merely a combination of spectra of ice and sulfuric acid tetrahydrate (SAT), as has been previously suggested could be the case by Zhang et al. (Zhang, R.; Wooldridge, P. J.; Abbatt, J. P. D.; Molina, M. J. J. Phys. Chem. 1993, 97, 7351). From our thermal analysis experiments, we have identified the melting transition of SAO. We report for the first time in the literature the enthalpy of fusion of SAO. We have also determined from our studies using the energies of fusion of ice and the various hydrates of H 2 SO 4 that SAO is a major component of H 2 SO 4 solutions in the range 20-40 wt % when they freeze. Our results indicate that SAO could be present in solid or partially frozen polar stratospheric and upper tropospheric cloud particles. Finally, we make a comment based on our results regarding the stoichiometric composition of SAO.

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Section: Resultssupporting

confidence: 89%

The Search for Sulfuric Acid Octahydrate: Experimental Evidence

2003

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“…In light of the newly proposed structures of the acid and its ions in water, I now reexamine some anomalous properties of the aqueous acid [18][19][20][21][22] and reveal parallels between the Raman scattering pattern and the peculiar change of the freezing point and electric conductivity of the aqueous acid as a function of concentration. The analysis of Young and Blatz 8 and the more recent data and their interpretation 14-17 thus deserve close reexamination.…”

Section: Purpose Of This Workmentioning

confidence: 99%

Structure and ionization of sulfuric acid in water

Fraenkel

2015

New J. Chem.

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Newly recorded Raman spectra of aqueous sulfuric acid provide scattering shifts of very high sensitivity hence signal-to-noise ratios, at a broad concentration range, up to 17 M. I interpret the spectra as (a) providing no evidence for incomplete H 2 SO 4 ionization at low concentration, (b) reflecting only one dissociation event below B5 M, (c) indicating a gradual ion association at B5-12.5 M, and (d) exhibiting further structural changes of the sulfate above 12.5 M. The analysis of the Raman shifts supports the postulated presence in solution of the para-bisulfate anion HSO 5 3À as a sole sulfate ion up to B5 M, as concluded before (D. Fraenkel, ion association producing para-sulfuric acid, H 4 SO 5 between 5 and 12.5 M, and a dehydration of H 4 SO 5 to H 2 SO 4 above 12.5 M. These conclusions are rationalized and corroborated by (1) a correlation of the Raman spectra with wellknown physicochemical properties of aqueous sulfuric acid, and (2) structural analogies between the proposed para-sulfates and related compounds and anions.

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“…For coastal ice cores, however, it seems reasonable to expect that the majority of Na + is deposited either as NaCl derived primarily from sea spray during storm activity (Legrand and Mayewski, 1997) or as sodium-sulfate salts such as mirabilite, Na 2 SO 4 · 10H 2 O, derived from brine rejection in sea ice or from atmospheric sea-salt sulfatization (Rankin et al, 2002;Iizuka et al, 2016). While the NaCl-H 2 O system reaches its eutectic at −21.3 • C (Stephen and Stephen, 1963), the eutectic of the Na 2 SO 4 -H 2 O system is −1.6 • C (Hougen et al, 1954), suggesting that Na + deposited as Na 2 SO 4 should be relatively immobile at most polar ice core sites. Consequentially, the majority of Na + relevant to grain boundary migration is likely derived from NaCl.…”

Section: Liquidus Relationships For Relevant Sea-salt Speciesmentioning

confidence: 99%

Methanesulfonic acid (MSA) migration in polar ice: data synthesis and theory

et al. 2017

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Abstract. Methanesulfonic acid (MSA; CH 3 SO 3 H) in polar ice is a unique proxy of marine primary productivity, synoptic atmospheric transport, and regional sea-ice behavior. However, MSA can be mobile within the firn and ice matrix, a post-depositional process that is well known but poorly understood and documented, leading to uncertainties in the integrity of the MSA paleoclimatic signal. Here, we use a compilation of 22 ice core MSA records from Greenland and Antarctica and a model of soluble impurity transport in order to comprehensively investigate the vertical migration of MSA from summer layers, where MSA is originally deposited, to adjacent winter layers in polar ice.We find that the shallowest depth of MSA migration in our compilation varies over a wide range (∼ 2 to 400 m) and is positively correlated with snow accumulation rate and negatively correlated with ice concentration of Na + (typically the most abundant marine cation). Although the considered soluble impurity transport model provides a useful mechanistic framework for studying MSA migration, it remains limited by inadequate constraints on key physicochemical parameters -most notably, the diffusion coefficient of MSA in cold ice (D MS ). We derive a simplified version of the model, which includes D MS as the sole parameter, in order to illuminate aspects of the migration process. Using this model, we show that the progressive phase alignment of MSA and Na + concentration peaks observed along a high-resolution West Antarctic core is most consistent with 10 −12 m 2 s −1 < D MS < 10 −11 m 2 s −1 , which is 1 order of magnitude greater than the D MS values previously estimated from laboratory studies. More generally, our data synthesis and model results suggest that (i) MSA migration may be fairly ubiquitous, particularly at coastal and (or) highaccumulation regions across Greenland and Antarctica; and (ii) can significantly change annual and multiyear MSA concentration averages. Thus, in most cases, caution should be exercised when interpreting polar ice core MSA records, although records that have undergone severe migration could still be useful for inferring decadal and lower-frequency climate variability.

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The Low Temperature Heat Capacity and Entropy of Sulfuric Acid Hemihexahydrate. Some Observations on Sulfuric Acid “Octahydrate”¹

Cited by 29 publications

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The Search for Sulfuric Acid Octahydrate: Experimental Evidence

The Search for Sulfuric Acid Octahydrate: Experimental Evidence

Structure and ionization of sulfuric acid in water

Methanesulfonic acid (MSA) migration in polar ice: data synthesis and theory

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The Low Temperature Heat Capacity and Entropy of Sulfuric Acid Hemihexahydrate. Some Observations on Sulfuric Acid “Octahydrate”1

Cited by 29 publications

References 0 publications

The Search for Sulfuric Acid Octahydrate: Experimental Evidence

The Search for Sulfuric Acid Octahydrate: Experimental Evidence

Structure and ionization of sulfuric acid in water

Methanesulfonic acid (MSA) migration in polar ice: data synthesis and theory

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The Low Temperature Heat Capacity and Entropy of Sulfuric Acid Hemihexahydrate. Some Observations on Sulfuric Acid “Octahydrate”¹