No description available.

Salt hydrates have the potential to be used in heat storage as both phase-change materials (PCMs) and thermochemical materials (TCMs). These materials offer advantages over traditional heat storage methods due to their high energy densities. However, both domestic and industrial applications require thousands of thermal cycles and there are often many issues that need to be overcome before these materials can be used reliably for heat storage. One of the major issues with using salt hydrates as PCMs is incongruency - the formation of anhydrous phases during melting. In this research, the mechanisms of the action of polymers to prevent incongruency in sodium acetate trihydrate have been investigated. A new polymorph of anhydrous sodium acetate, Form IV, was obtained in the presence of the polymer. This polymorph crystallises as long, blade-shaped crystals, thereby increasing the surface area to volume ratio. Indexing of the crystal faces revealed that every face had Na+ or the oxygen atoms of the acetate ion near or on the surface, as opposed to hydrophobic methyl groups found on the faces of the anhydrous salt grown without polymer. These two factors are believed to significantly increase the dissolution kinetics. This technique has the potential to be used for screening polymers to reformulate other salt hydrates that display incongruent behaviour. Eutectic compositions of NaCl and KCl with strontium hydroxide octahydrate were investigated as a potential means to prevent the incongruency of this PCM. However, degradation was observed with thermal cycling. Variable temperature PXRD studies discovered a new Sr(OH)2 hydrate when heating above 75 °C - Sr(OH)2. ⅓H2O. The recrystallisation of the octahydrate from the new phase was slow with incomplete conversion, explaining the degradation with continuous cycling. The effect of addition of NaCl and KCl to congruent barium hydroxide octahydrate was also investigated. On heating, a phase transition was observed, but the samples remained solid. Variable temperature PXRD investigations discovered that this was due to the formation of the salt hydrate, Ba(OH)Cl.2H2O. This hydrate melted at 110 °C, showing its potential as a high temperature PCM. The dehydration pathways of magnesium sulfate heptahydrate were investigated. In-situ PXRD studies showed that changing the heating rate changed the intermediates present during the dehydration. The fast dehydration rate saw both the known phases of trihydrate and 2.5 hydrate form as the dehydration product of the tetrahydrate. These both then dehydrated to the known dihydrate. This differed when the slower heating rate was used, as the trihydrate was the only product of dehydration from the tetrahydrate. The trihydrate then proceeded to dehydrate to a new phase. This was found to be a new polymorph of the dihydrate, β-MgSO4.2H2O. Dehydration of MgSO4.7H2O with 50 mol% NaCl was also performed. Loeweite, Na12Mg7(SO4)13.15H2O, a dication sulfate hydrate, was formed as the major intermediate. This mixture showed advantages over the pure MgSO4.7H2O as dehydration to the monohydrate took less time and occurred at a lower temperature. There were also three fewer intermediate phases before dehydration to the monohydrate. Suspension and encapsulation materials were used in order to overcome the major issue of agglomeration with magnesium sulfate. Liquid water was ruled out as a viable hydration medium. Apparatus was developed to test humidity cycling, which allowed the effects of dehydration time and temperature to be investigated, as well testing a range of different formulations.

There is a current requirement for technologies that store heat for both domestic and industrial applications. Phase-change materials (PCMs) represent an important class of materials that offer potential for heat storage. Heat-storage systems are required to undergo multiple melt/freeze cycles without any change in melting-crystallisation point and heat output. Salt hydrates are attractive candidates on account of their high energy densities, but there are issues associated with potential crystallisation of lower-hydrates, long-term stability, and reliable nucleation. An extensive review of the PCMs in the literature, combined with an evaluation of commercially available PCMs led to the conclusion that many of the reported PCMs, lack at least one of the key requirements required for use as a heat-storage medium. The focus of this research was therefore to identify and characterise new PCM compositions with tailored properties. New PCM compositions based of sodium acetate trihydrate were developed, which showed improved properties through the use of selective polymers that retard the nucleation of undesirable anhydrous sodium acetate. Furthermore, the mechanism of nucleation of sodium acetate trihydrate by heterogeneous additives has been investigated using variable-temperature powder X-ray diffraction. This study showed that when anhydrous Na2HPO4 was introduced to molten sodium acetate trihydrate at 58°C the hydrogenphosphate salt is present as the dihydrate. On heating to temperatures in the range 75-90°C the dihydrate was observed to dehydrate to form anhydrous Na₂HPO4. This result explains the prior observation that the nucleator is deactivated on heating. The depression of melting point of sodium acetate trihydrate caused by the addition of lithium acetate dihydrate has also been investigated using differential scanning calorimetry and powder X-ray diffraction. It has been possible to tune the melting point of sodium acetate trihydrate thereby modifying its thermal properties. Studies of the nucleation of sodium thiosulfate pentahydrate, a potential PCM, led to the structural characterisation of six new hydrates using single crystal Xray diffraction. All of these hydrates can exist in samples with the pentahydrate composition at temperatures ranging from 20°C to 45°C. These hydrates are: α-Na₂S₂O₃·2H₂O, which formed during the melting of α-Na₂S₂O₃·5H₂O; two new pentahydrates, β-Na₂S₂O₃·5H₂O and γ-Na₂S₂O₃·5H₂O; Na₂S₂O₃·1.33 H₂O, β-Na₂S₂O₃·2H₂O and Na₂S₂O₃·3.67 H₂O, which formed during the melting of β- Na₂S₂O₃·5H₂O. Furthermore, new PCMs in the 75-90°C range were identified. The commercial impact and route to market of several of the PCMs are discussed in the final chapter.

X-ray diffraction from protein crystals remains the most reliable way to determine the molecular structure of proteins, and how this structure relates to biological function. However, we still lack the ability to predict solution conditions that support the nucleation and growth of high-quality protein crystals for X-ray diffraction studies. The overall goal of this thesis is two-fold: (a) determine the nucleation behavior and solubilities for lysozyme crystals with two distinct crystal structures (orthorhombic vs. tetragonal) and (b) investigate whether these changes in crystal habit and crystal solubility correlate with any discontinuities in the liquid-liquid phase boundary of lysozyme that occurs under the same solution conditions. We measured lysozyme crystal solubility by nucleating and subsequently dissolving very small lysozyme crystals in highly supersaturated solutions. The presence of crystals in our samples is detected and monitored by measuring the light scattered off the micron-sized crystals. These "turbidity measurements" are repeated across a range of protein concentrations, for pH 4.6 and 5.6, thereby yielding the crystal solubility boundary. Changes in crystal structure are assessed at the end of the experiments by microscopic inspection of the distinct crystal habits. Attractive protein interactions in solution also induce liquid-liquid phase separation. Similar to the crystal solubility measurement, we use the turbidity increase associated with liquid-liquid phase separation to map out this phase boundary. Since both crystal formation and liquid-liquid phase separation are driven by attractive protein interactions, we investigated whether the dramatic changes in crystal solubility associated with different protein crystal structures lead to any discernable “discontinuities” in the liquid-liquid phase boundaries.

The objective of this study was to determine the effect of vacuum packaging and 100% CO₂ with and without sodium lactate (0%, 2.4%, 4.8%), sodium acetate (0%, 0.25%, 0.50%), and sodium diacetate (0%, 0.25%, 0.50%) on the inhibition of L. monocytogenes on turkey frankfurters. After 4 weeks at 4°C, the counts of L. monocytogenes did not increase in any treatment, including the control. The use of sodium lactate (4.8%), sodium acetate (0.5%), and sodium diacetate (0.5%) provided approximately a 0.5 log10 CFU/g decrease when compared to the control; however, there was not a significant (P > 0.05) difference between the control and the samples using sodium acetate (0.25%), sodium diacetate (0.25%), or sodium lactate (2.4%). There was also no significant difference between the samples packaged in 100% CO₂ or under vacuum (P > 0.05). After 4 weeks at 10°C, growth of L. monocytogenes was approximately 1-1.5 log lower on the frankfurters packaged in 100% CO₂ than those packaged in a vacuum atmosphere (P £ 0.001). Sodium acetate (0.5%) and sodium lactate (2.4%) in combination with a high CO₂ atmosphere prevented any increase in L. monocytogenes numbers for up to 4 weeks at 10°C. The use of sodium lactate (4.8%) and sodium diacetate (0.5%) in combination with a high CO₂ atmosphere resulted in a decrease in numbers of L. monocytogenes on the frankfurters by ~0.5 log (P £ 0.001). Strict temperature control is needed to prevent the growth of L. monocytogenes. A high CO₂ atmosphere in combination with antimicrobials may assist in keeping the numbers of the organism in the food low in the case of product contamination and temperature abuse. / Master of Science

Submitted by Marlene Santos (marlene.bc.ufg@gmail.com) on 2017-09-21T20:27:37Z No. of bitstreams: 2 Tese - Fabiana Ribeiro da Mata - 2017.pdf: 5224228 bytes, checksum: 062f7a43994431350fa0acd55b4f076c (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-09-22T11:44:01Z (GMT) No. of bitstreams: 2 Tese - Fabiana Ribeiro da Mata - 2017.pdf: 5224228 bytes, checksum: 062f7a43994431350fa0acd55b4f076c (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-09-22T11:44:01Z (GMT). No. of bitstreams: 2 Tese - Fabiana Ribeiro da Mata - 2017.pdf: 5224228 bytes, checksum: 062f7a43994431350fa0acd55b4f076c (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-04-13 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG / Members of the genus Paracoccidioides are known pathogens of humans that can be isolated from different infection sites. To investigate the expression rates of proteins expressed by different isolates, of the genus Paracoccidioides, including one isolate of P. lutzii (Pb01), and three isolates of P. brasiliensis (Pb03, Pb339 and PbEPM83) using sodium acetate, as carbon source, proteins quantities were determined using label-free and data independent LC-MSE. Statistical analysis provided the comparison of proteins profiles in the isolates. A total of 1160, 1211, 1280 and 1462 proteins were reproducibly identified, and relatively quantified in P. lutzii e P. brasiliensis isolates Pb03, Pb339 e PbEPM83, respectively. Notably, a total of 526, 435, 744 and 747 proteins were differentially expressed among P. lutzii and the P. brasiliensis isolates Pb03, Pb339 and PbEPM83, respectively with a fold change equal or higher than 1.5. The analysis revealed the reorganization of metabolism through the induction of proteins related to gluconeogenesis, stress response and amino acid degradation in the four isolates evaluated. The differences between the isolates were observed as follows: greater increases in the expression levels of proteins belonging to the cycle of glyoxalate, TCA and respiratory chain, ethanol production and β-oxidation were observed in the isolatesPPEPM83 and Pb01; Cyclic and cyclocyclic proteins of the methylcitrate were induced in Pb339. Proteomic profiles indicate that the four isolates reorganize the metabolism for the use of acetate as a carbon source. / Membros do gênero Paracoccidioides são patógenos conhecidos de seres humanos que podem ser isolados de diferentes locais de infecção. Para investigar as taxas de expressão das proteínas expressas por diferentes isolados, do gênero Paracoccidioides, incluindo um isolado de P. lutzii (Pb01) e três isolados de P. brasiliensis (Pb03, Pb339 e PbEPM83) usando acetato de sódio, como fonte de carbono, As quantidades de proteínas foram determinadas usando o uso de LC-MSE independente de etiquetas e de dados. A análise estatística proporcionou a comparação de perfis de proteínas nos isolados. Um total de 1160, 1211, 1280 e 1462 proteínas foram identificadas de forma reprodutiva, e relativamente quantificadas em isolados de P. lutzii e P. brasiliensis Pb03, Pb339 e PbEPM83, respectivamente. Nomeadamente, um total de 526, 435, 744 e 747 proteínas foram diferencialmente expressas entre P. lutzii e os isolados de P. brasiliensis Pb03, Pb339 e PbEPM83, respectivamente, com uma mudança de dobra igual ou superior a 1,5. A análise revelou a reorganização do metabolismo através da indução de proteínas relacionadas à gliconeogênese, resposta ao estresse e degradação de aminoácidos nos quatro isolados avaliados. As diferenças entre os isolados foram observadas como segue: maiores aumentos nos níveis de expressão de proteínas pertencentes ao ciclo do glioxalato, TCA e cadeia respiratória, produção de etanol e β-oxidação foram observadas nos isoladosnPbEPM83 e Pb01; As proteínas do ciclo da e do ciclo do metilcitrato apresentaram induzidas no Pb339. Os perfis proteômicos indicam que os quatro isolados reorganizam o metabolismo para o uso do acetato como fonte de carbono.

Orientadores: Osvaldir Pereira Taranto, Marcelo Nitz da Costa / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-12T09:06:35Z (GMT). No. of bitstreams: 1 Souza_LucianeFranquelinGomesde_M.pdf: 4524135 bytes, checksum: 1ae4c10ba2c2ed03a7393643ced61a02 (MD5) Previous issue date: 2008 / Resumo: Acetato de sódio e um sal orgânico produzido pela reação do acido acético com hidróxido de sódio. Depois da cristalização e separação os cristais úmidos são secos. Já o cloreto de potássio e um sal inorgânico extraído de rochas e águas salinas muito utilizado na industria química como fertilizante. Esses sais são higroscópicos, coesivos quando úmidos, e geralmente são secos em secadores de leitos fluidizados. No presente trabalho foi utilizado um secador de leito pulso-fluidizado (PFB) que e uma modificação do secador de leito fluidizado convencional. Neste equipamento uma taxa constante de ar e suprido para o secador. Um distribuidor de gás instalado sob a câmara de secagem promove a pulsação pela corrente de gás alternada. A principal vantagem desta técnica e o uso de uma vazão de ar menor quando comparada com outras. O PFB utilizado neste trabalho possui uma área de secção transversal de 0,18 metros quadrados e constituído de quatro seções. Inicialmente foi realizado o estudo fluidodinâmico dos sais secos e úmidos. Posteriormente as curvas de secagem do acetato de sódio e cloreto de potássio foram determinadas para diferentes condições de secagem (temperatura do ar e freqüência de pulsação). A secagem e fluidodinâmica em leito fluidizado convencional foram feitas para que a comparação com o leito pulsado fosse possível. Resultados mostraram que as taxas de secagem foram maiores na fluidizarão pulsante devido ao melhor comportamento fluidodinâmico: o fluxo intermitente ajuda a romper partículas aglomeradas e conseqüentemente prover melhor contato entre gás - partícula. / Abstract: Sodium acetate is a salt produced by the reaction of acetic acid with sodium hydroxide. After crystallization and separation, the wet crystals are dried. Potassium chloride is an inorganic salt extracted from rocks and saline water. It is mainly used in the chemical industry as a fertilizer. These salts are hygroscopic particulate materials, which are dried in fluidized beds or rotary dryers. In this work a pulsed-fluid bed (PFB) dryer was used, which is a variation of the conventional fluidized bed dryer. In this equipment, a constant airflow rate is supplied to the dryer. A gas distributor installed upstream of the drying chamber provides the pulsed-flow by alternating the gas stream. The main advantage of this technique is the lower airflow rate supplied when compared with competitive techniques. The PFB used in this work has a cross section area of 0.18 m2 and it has four sections. Initially, the fluid-dynamic study of dry and wet salts was performed. Subsequently the drying curves of sodium acetate and potassium chloride were determined for different drying conditions (inlet air temperature and pulsation frequency). Drying and Fluid-dynamic was performed in conventional fluidized bed drying, so that results could be compared. Results showed that the drying rates were higher under pulsed fluidization due to the better fluid-dynamic behavior: the intermittent flow can help to break particle agglomerates and therefore provide better contact between particles and the gas. / Mestrado / Engenharia de Processos / Mestre em Engenharia Química

Resumo: Existem vários extratores que avaliam a disponibilidade de silício no solo. Nos Estados Unidos utiliza-se como extrator químico o ácido acético 0,5 mol L-1 , o qual já foi usado no Brasil, mas recentemente foi substituído pelo cloreto de cálcio 0,01 mol L-1, o mesmo utilizado na Austrália. Os extratores, de forma geral, são dependentes das características físicas do solo, principalmente do teor de argila, e podem subestimar ou superestimar os teores de silício no solo. Na literatura não há relatos de extratores de silício que se assemelhem às raízes das plantas, como é o caso da resina trocadora de ânions usada na extração do fosfato do solo. Dessa forma, o objetivo deste trabalho foi avaliar extratores químicos que correlacionem o silício disponível no solo com o silício absorvido por plantas de cana-de-açúcar, cultivada em solos de textura arenosa, média e argilosa. Foram avaliados 8 extratores com o objetivo de selecionar aqueles que melhor avaliam os diferentes tipos de solos encontrados no Brasil. Os extratores utilizados foram CaCl2 0,01 Mol L-1 (Padrão), CaCl2 0,01 Mol L-1 (modificado), ácido acético 0,5 Mol L-1, KCl 0,01 Mol L-1, resina trocadora de íons, água, tampão acetato de sódio pH 4,0 e HCl 0,01 Mol L-1. As amostras foram coletadas entre março e dezembro de 2007 em áreas cultivadas com a cultura da cana-de-açúcar nas Usinas Guairá (Guairá-SP) e Colombo (Ariranha - SP). No momento do corte de cana-de-açúcar, em cada unidade experimental, foram realizadas coletas de solo nas profundidades 0-0,20 m e 0,20-0,40 m, para avaliação de pH, M.O. H+Al, P, K, Ca, Mg, Si, Fe2O3, Al2O3, SiO2 e textura do solo. Na mesma época, coletou-se a parte aérea de 10 plantas inteiras de cana-de-açúcar para determinação da produtividade e do silício acumulado nas plantas. As texturas dos solos... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Many extractants evaluated silicon availability in soil. In the United States, the acetic acid 0.5 mol L-1 is the most used. This Si extractant has already been used in Brazil, but it was recently replaced by the calcium chloride 0.01 mol L-1, the same used in Australia. The extractants generally depend on soil physical characteristics, mainly clay content, and thus may underestimate or overestimate Si levels in soil. There are no references in literature about silicon extractants that simulate the behavior of plant roots, like the anion exchange resin used to extract phosphate in soil. Therefore, the objective of this study was to evaluate chemical extractants that correlate Si available in soil with Si uptaken by sugar cane plants, cropped in sandy, sandy-loam and clayey soils. Eight Si extractants were tested with the aim to select the ones that most accurately evaluate different soil types in Brazil. The extractants were CaCl2 0.01 Mol L-1 (standard), CaCl2 0.01 Mol L-1 (modified), acetic acid 0.5 Mol L-1, KCl 0.01 Mol L-1, ion exchange resin, water, sodium acetate buffer pH 4.0 and HCl 0.01 Mol L-1. Samples were taken in Guaíra-SP, Brazil (Usina Guaíra) and Ariranha-SP, Brazil (Usina Colombo) between March and December of 2007 from areas cropped with sugar cane. At harvest, soil samples were taken from each experimental unit in the depths 0-0.20 m and 0.20-0.40 m to evaluate pH, organic matter (O.M.), H+Al, P, K, Ca, Mg, Si, Fe2O3, Al2O3, SiO2 and soil texture. Also, 10 plant shoots were harvested to determine yield and Si accumulation. Soil texture, iron oxide and aluminum oxide levels significantly influence on Si availability in soil. The acetic acid and buffer pH 4.0 extracted more silicon from soil, mainly in the clayey texture, that showed high levels of iron and aluminum oxides, highly correlating with Si accumulated in plant... (Complete abstract click electronic access below) / Orientador: Carlos Alexandre Costa Crusciol / Coorientador: Dirceu Maximino Fernandes / Banca: Iraê Amaral Guerrini / Banca: Gaspar Henrique Korndorfer / Mestre

Made available in DSpace on 2014-06-11T19:24:43Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-08-31Bitstream added on 2014-06-13T18:52:34Z : No. of bitstreams: 1 arruda_dp_me_botfca.pdf: 628799 bytes, checksum: c0a1f52e914545883936131898e973ff (MD5) / Existem vários extratores que avaliam a disponibilidade de silício no solo. Nos Estados Unidos utiliza-se como extrator químico o ácido acético 0,5 mol L-1 , o qual já foi usado no Brasil, mas recentemente foi substituído pelo cloreto de cálcio 0,01 mol L-1, o mesmo utilizado na Austrália. Os extratores, de forma geral, são dependentes das características físicas do solo, principalmente do teor de argila, e podem subestimar ou superestimar os teores de silício no solo. Na literatura não há relatos de extratores de silício que se assemelhem às raízes das plantas, como é o caso da resina trocadora de ânions usada na extração do fosfato do solo. Dessa forma, o objetivo deste trabalho foi avaliar extratores químicos que correlacionem o silício disponível no solo com o silício absorvido por plantas de cana-de-açúcar, cultivada em solos de textura arenosa, média e argilosa. Foram avaliados 8 extratores com o objetivo de selecionar aqueles que melhor avaliam os diferentes tipos de solos encontrados no Brasil. Os extratores utilizados foram CaCl2 0,01 Mol L-1 (Padrão), CaCl2 0,01 Mol L-1 (modificado), ácido acético 0,5 Mol L-1, KCl 0,01 Mol L-1, resina trocadora de íons, água, tampão acetato de sódio pH 4,0 e HCl 0,01 Mol L-1. As amostras foram coletadas entre março e dezembro de 2007 em áreas cultivadas com a cultura da cana-de-açúcar nas Usinas Guairá (Guairá-SP) e Colombo (Ariranha - SP). No momento do corte de cana-de-açúcar, em cada unidade experimental, foram realizadas coletas de solo nas profundidades 0-0,20 m e 0,20-0,40 m, para avaliação de pH, M.O. H+Al, P, K, Ca, Mg, Si, Fe2O3, Al2O3, SiO2 e textura do solo. Na mesma época, coletou-se a parte aérea de 10 plantas inteiras de cana-de-açúcar para determinação da produtividade e do silício acumulado nas plantas. As texturas dos solos... / Many extractants evaluated silicon availability in soil. In the United States, the acetic acid 0.5 mol L-1 is the most used. This Si extractant has already been used in Brazil, but it was recently replaced by the calcium chloride 0.01 mol L-1, the same used in Australia. The extractants generally depend on soil physical characteristics, mainly clay content, and thus may underestimate or overestimate Si levels in soil. There are no references in literature about silicon extractants that simulate the behavior of plant roots, like the anion exchange resin used to extract phosphate in soil. Therefore, the objective of this study was to evaluate chemical extractants that correlate Si available in soil with Si uptaken by sugar cane plants, cropped in sandy, sandy-loam and clayey soils. Eight Si extractants were tested with the aim to select the ones that most accurately evaluate different soil types in Brazil. The extractants were CaCl2 0.01 Mol L-1 (standard), CaCl2 0.01 Mol L-1 (modified), acetic acid 0.5 Mol L-1, KCl 0.01 Mol L-1, ion exchange resin, water, sodium acetate buffer pH 4.0 and HCl 0.01 Mol L-1. Samples were taken in Guaíra-SP, Brazil (Usina Guaíra) and Ariranha-SP, Brazil (Usina Colombo) between March and December of 2007 from areas cropped with sugar cane. At harvest, soil samples were taken from each experimental unit in the depths 0-0.20 m and 0.20-0.40 m to evaluate pH, organic matter (O.M.), H+Al, P, K, Ca, Mg, Si, Fe2O3, Al2O3, SiO2 and soil texture. Also, 10 plant shoots were harvested to determine yield and Si accumulation. Soil texture, iron oxide and aluminum oxide levels significantly influence on Si availability in soil. The acetic acid and buffer pH 4.0 extracted more silicon from soil, mainly in the clayey texture, that showed high levels of iron and aluminum oxides, highly correlating with Si accumulated in plant... (Complete abstract click electronic access below)

Aqueous solutions of sodium acetate, NaCH₃CO₂, and acetic acid, CH₃COOH, were studied using Raman and infrared spectroscopy. The spectra were recorded over a large concentration range, in the terahertz region and up to 4000 cmˉ¹. In the isotropic Raman spectrum in R-format, a polarized band at 189 cmˉ¹ was assigned to the υ₁Na–O stretch of the hydrated Na⁺-ion and a shoulder at 245 cmˉ¹ to the restricted translation band, υsO–H⋯O* of the hydrated acetate ion, CH₃CO₂ˉ(aq). The CH₃CO₂ˉ(aq) and the hydrated acetic acid, CH₃COOH(aq), possess pseudo Cs symmetry. Geometrical parameters for the species in the gas phase and for CH₃CO₂ˉ(aq) and CH₃COOH(aq) are reported. Characteristic bands for CH₃CO2ˉ(aq) and CH₃COOH(aq) were assigned under the guidance of the DFT vibrational frequency calculations and discussed in detail. In aqueous NaCH₃CO₂ solutions, at high concentrations, no contact ion pairs could be detected, but instead solvent separated ion pairs were found. In LiCH₃CO₂(aq), however, contact ion pairs are formed which is indicated by the appearance of a shoulder at 939 cmˉ¹ and the shift of the symmetric stretching mode of the –CO₂ˉ group to higher wavenumbers.