Letteratura scientifica selezionata sul tema "Formiate de calcium"

Centimeter-sized crystals of orthorhombic calcium formate, α-Ca(HCO2)2 from Alkali Lake, Oregon, USA have been studied by means of powder and single-crystal X-ray diffraction analysis, infrared, and Raman spectroscopy. Based on the data on carbon isotope abundance in calcium formate and associated minerals, it was concluded that the formation of α-Ca(HCO2)2 may be a result of a combination of two factors: lake microbial metabolism and anthropogenic pollution with Agent Orange. Possible causes of stability of the low-density tetragonal β-Ca(HCO2)2 polymorph (formicaite) in boron ores are discussed.

Selulosa adalah polisakarida rantai panjang penyusun serat pada tumbuhan. Hidrolisis selulosa dengan alkali kuat menghasilkan asam oksalat, asam asetat dan asam formiat. Limbah serbuk kayu jati berpotensi untuk dijadikan bahan baku pembuatan asam oksalat karena kandungan selulosa yang cukup tinggi. Hidrolisis yang dilakukan pada penelitian ini menggunakan natrium hidroksida (NaOH) sebagai zat penghidrolisis. Purifikasi asam oksalat dilakukan dengan penambahan kalsium klorida dan asam sulfat. Penelitian ini mempelajari pengaruh konsentrasi natrium hidroksida dan waktu reaksi terhadap yield asam oksalat. Produk tertinggi dengan yield 20% dicapai pada penggunaan serbuk kayu jati kasar dengan waktu hidrolisis 60 menit dan konsentrasi NaOH 1 N.Cellulose is a long chain fiber polysaccharide contained in plants. Hydrolysis of cellulose with strong alkali produces oxalic acid, acetic acid and formic acid. Waste from teak wood in powder formhas the potential to be used as raw material for the manufacture of oxalic acid because the content of cellulose is high enough. Sodium hydroxide (NaOH) as a hydrolysis agent was used in this study. Purification of formed oxalic acid was carried out by addition of calcium chloride and sulfuric acid. Our research studied the effect of sodium hydroxide concentration and reaction time on oxalic acid yield. The highest product with a yield of 20% was achieved on the use of coarse powder of teak wood waste with a hydrolysis time of 60 minutes and the concentration of NaOH 1 N.

It is well-known that the incidence of milk fever in dairy cows can be significantly reduced when gut absorption of approximately 50g calcium takes place 4 times with 12 hour intervals around calving.1,2,3 There are several different oral calcium formulations available containing different calcium salts, e.g., chloride, propionate, formiate, oxide, and carbonate. The amount of absorbed calcium following oral administration, however, is dependent on water- solubility of the different salts. 4 Calcium chloride is the most readily absorbed salt. The bioavailability of calcium propionate and formiate are inferior to calcium chloride. Consequently, a higher amount of administered calcium salts like calcium propionate or formia te is needed in order to get approximately 50g calcium absorbed from the gut. Calcium oxide and calcium carbonate are not water-soluble and therefore poorly absorbed. It is also well-known that due to its caustic effect, calcium chloride in water or watery gel causes serious mucosal damages in the pharynx, esophagus, forestomachs and abomasum.5'6 Several of these products in Europe are withdrawn from the market due to the caustic effect of calcium chloride on the mucosa. A calcium chloride bolus with a protective layer of fat surrounding it is available in Scandinavia. However, serious consequences are reported following administration of the calcium bolus to calving cows with impaired or absent mobility of the digestive tract. In these cases the bolus or boli lie directly on the mucosa in either rumen or reticulum, and the caustic calcium chloride would be in direct contact with the mucosa. A fatal case report is published in the Danish Veterinary Journal.7 A water-in-oil emulsion, where the caustic calcium chloride is dissolved in water and protected by oil, has been on the market during the past 6-7 years. The mucosal damages are minimized following administration. Maladministration into the lungs, however, has been observed due to the viscosity of the product.8 In cooperation with the Royal Danish School of Pharmacy, a calcium chloride paste formulation (BOVIVET® Calcium Paste, Jørgen Kruuse A/S) has been developed. In this paste formulation 180g calcium chloride and 6g magnesium chloride are distributed in and protected by a special two-component oil preparation and filled on to a 255ml cartridge. During the production of the paste formulation the dry materials are sticked together with the fat part of the oil which is then covered by rape seed oil. This publication describes an investigation of possible mucosal damages of the tongue, pharynx, larynx, oesophagus, forestomachs and abomasum following oral administration of the calcium chloride paste formulation 4 times with 12 hours interval.

L'apparition d'efflorescences cristallines sur des objets calcaires stockés dans des environnements pollués, communément appelée "dégradation de Byne", résulte de l'émission de composés organiques volatils (COV) acides par les matériaux de stockage. Ces acides réagissent avec le carbonate de calcium en formant des sels organiques de calcium, dont des acétates et des sels mixtes acétate-formiate, qui provoquent une détérioration irréversible du substrat. Jusqu'à présent, seuls des objets macroscopiques subissant la dégradation de Byne avaient été décrits dans la littérature.Ce travail vise à comprendre comment la dégradation de Byne peut aussi affecter des spécimens calcaires microscopiques présents dans les collections de micropaléontologie. Il a été initié par la numérisation de la collection de foraminifères d'Alcide d'Orbigny (1802-1857), conservée au Muséum national d'Histoire naturelle (MNHN), qui a révélé des dommages importants liés à la présence d'efflorescences salines.Un constat d'état a été mené sur l'ensemble de la collection d'Orbigny (plus de 3600 spécimens), mettant en évidence que les altérations, à la fois anciennes et évolutives, sont influencées par la cristallinité des tests et l'origine des lieux de prélèvement des foraminifères. Des collections voisines ont été examinées à titre comparatif et des recherches en archives ont permis de retracer l'histoire de la collection depuis son entrée au MNHN. Elles mettent en évidence de nombreux déménagements et des accidents tels que la crue de la Seine de 1910, qui expliquerait l'humidité particulièrement élevée à l'intérieur des tubes où sont conservés les foraminifères. Des variations importantes de température, combinées à la présence de matériaux émetteurs de COV introduits à la fin du XIXe siècle dans le montage des spécimens, sont ainsi à l'origine de la pollution acide et de la prolifération des sels.Parallèlement à cela, une procédure de vieillissement artificiel a été élaborée pour reproduire la dégradation de Byne sur des foraminifères sains. Les produits de dégradation formés sur les spécimens vieillis, ainsi que sur une sélection représentative de spécimens historiques, ont été analysés de manière non invasive et sans contact par spectroscopie micro-Raman et par diffraction des rayons X sur rayonnement synchrotron. Ces analyses ont mis en évidence des phases minéralogiques différentes de celles observées dans la littérature sur les collections macroscopiques. Ce sont ainsi des formiates de calcium qui prédominent, et tout particulièrement le polymorphe tétragonal [β-Ca(HCOO)2] connu pour être instable lorsqu'il est synthétisé en laboratoire. Aucun acétate ou sel mixte de calcium n'a pu être identifié sur les foraminifères de la collection d'Orbigny. Les vieillissements montrent que l'humidité relative et la taille des spécimens jouent un rôle primordial dans la formation des sels : des conditions humides favorisent la cristallisation du formiate de calcium sur le spécimen, tandis que l'acétate, très hygroscopique, est sujet aux cycles de déliquescence-cristallisation qui le conduisent à se disperser autour de l'échantillon lorsque celui-ci est de très petite taille.Enfin, pour mieux comprendre la prédominance du formiate de calcium [β-Ca(HCOO)2], différentes solutions de formiate de calcium ont été laissées à évaporer et placées dans des environnements à humidité variée afin d'étudier la transformation vers la phase stable [α-Ca(HCOO)2]. L'analyse semi-quantitative des produits montre que la présence d'ions tels que ceux trouvés dans les coquilles de foraminifères (Mg2+, Sr2+...) favorise la formation de la phase métastable, et ralentit la transition β-->α.Ce travail montre que la nature des sels formés par la dégradation de Byne n'est pas seulement tributaire des COV présents mais dépend aussi de la taille des spécimens, leur composition, la cristallisation de leur test et des cycles d'humidité et de température auxquels ils ont été soumis
The appearance of crystalline efflorescence on calcareous objects stored in polluted environments is commonly referred to as "Byne's decay". It results from the emission of acidic volatile organic compounds (VOCs) from storage materials, which react with calcium carbonate to form organic calcium salts. This includes acetates and mixed acetate-formate salts that cause irreversible deterioration of the substrate. Until now, only macroscopic objects undergoing Byne's decay had been reported in the literature.This work focuses on how Byne's decay can also affect microscopic calcareous specimens from micropaleontology collections. It was initiated by the digitization of the foraminifera collection of Alcide d'Orbigny (1802-1857), housed at the Muséum national d'Histoire naturelle (MNHN), which revealed significant damage due to the presence of saline efflorescences.A condition report was carried out on the whole of the d'Orbigny collection (more than 3600 specimens), highlighting that the alterations, both ancient and evolutionary, are influenced by the crystallinity of the tests and the origin of the places where the foraminifera were collected. Similar collections closely located were examined for comparison and archival research was conducted to trace the material history of the collection since its entry into the MNHN. They highlight several moves and accidents such as the flooding of the Seine in 1910, which would explain the particularly high levels of humidity inside the tubes where the foraminifera are kept. Significant variations in temperature, combined with the presence of VOC-emitting materials introduced at the end of the 19th century in the assembly of the specimens, are thus at the origin of the acid pollution and the proliferation of salts.At the same time, an artificial aging procedure was developed to reproduce Byne's decay on unaltered specimens. The degradation products formed on the aged specimens, as well as on a representative selection of historical ones, were analysed non-invasively and without contact by using micro-Raman spectroscopy and synchrotron X-ray diffraction. These analyses revealed mineralogical phases different from those observed in the literature on macroscopic collections. Thus, calcium formates and especially the tetragonal polymorphic phase [β-Ca(HCOO)2] known to be unstable when synthesized in laboratory conditions, predominate. No calcium acetate or mixed salt could be identified on d'Orbigny's foraminifera. Aging shows that the relative humidity and the size of the specimens play a primordial role in the formation of the salts: humid conditions favour the crystallization of calcium formate directly on the specimen, while acetate, very hygroscopic, is subject to deliquescence-crystallization cycles that lead to its redispersion around micrometer-scale specimens.Finally, to better understand the predominance of calcium formate [β-Ca(HCOO)2], different calcium formate solutions were left to evaporate and placed in environments with different humidity to study the transformation towards the stable phase [α-Ca(HCOO)2]. Semi-quantitative analysis of the products shows that the presence of ions such as those found in foraminiferal shells (Mg2+, Sr2+…) favours the formation of the metastable phase and slows down the transition β-->α.This work shows that the nature of the salts formed by Byne's decay is not only dependent on the VOCs present, but also on the size of the specimens, their composition, their test crystallization, and the moisture and temperature cycles to which they were exposed