Abstract
Trisodium citrate C6H5O7Na3 is one of the most widely used synthetic chemicals in the laboratory as raw materials to synthesize some metals-citricacid-oxides and also to control the acidity of certain substances and/or solutions; thus it is rare to find it in stock at suppliers. That was why synthesizing this product in laboratory came suddenly in the head and ended up being realized within certain experimental conditions such as: the synthesis was carried out at room temperature, under atmospheric pressure, the initial concentration of sodium hydroxide 4.38 twice higher was relatively in excess against citric acid and using ethanol-90° as solvent. It consisted of mixing citric acid with sodium hydroxide 99% purity, and ethanol 90% purity which served as a solvent. In fact, the two raw materials, citric acid and sodium hydroxide are all soluble in ethanol while the desired product trisodium citrate isn’t insoluble in this solvent-ethanol. The calculated initial pH of the raw materials solution was 15.21 and the solvent-ethanol quantities was evaluated so that eventual water molecules and eventual sodium ethoxide formed during the synthesis were soluble in it. Thus, all synthesized trisodium citrate crystals insoluble in ethanol were located at the bottom and separated. To quantify all these synthesized trisodium citrate-C6H5O7Na3 crystals, a titration procedure using hydrochloric acid HCl-0.1N was established. Application of this established titration procedure allowed to follow the reaction with time and consequently to evaluate the speed constant of this reaction synthesis of trisodium citrate-C6H5O7Na3 crystals under these previous experimental conditions which was equal to 1.56E-2 [L2×mol-2×s-1]. Also, the initial speed formation of synthesized sodium ethoxide was equal to 0.0027 [mol×l-1×s-1] and the citric acid conversion only after 30 minutes of reaction was 92.56%. The evaluation of this synthesized trisodium citrate crystals porosity was done by immersion in an isopropyl alcohol giving a value in the order of 48,67% and density equal to 1.79[g/cm3].
Highlights
This laboratory synthesis of trisodium citrate crystals C6H5O7Na3 was carried out using sodium hydroxide (99% purity) relatively in excess 4.38 twice higher over citric acid with ethanol (90% purity) as a solvent
According to the enthalpies of formation of the compounds on the reaction (1) given by bibliographies [12,13,14,15], the standard enthalpy of this reaction was equal to +1970.906[Kj/mol]. These results indicated and confirmed that this reaction is slightly endothermic [14], and the present experimental conditions and procedure with the solvent-ethanol 90° put together were efficient to produce the trisodium citrate
The synthesized trisodium citrate was white and its concentrated solution 0.6914[mol.l-1] obtained by dissolving them in distillated water had 1.3510 refractive index. Noticed that this value of refractive index was less than for the trisodium citrate di-hydrate in the bibliography (1.58) [18] certainly because of the dissolution in distillated water which decrease its refractive index as showed in bibliography [19]
Summary
This laboratory synthesis of trisodium citrate crystals C6H5O7Na3 was carried out using sodium hydroxide (99% purity) relatively in excess 4.38 twice higher over citric acid with ethanol (90% purity) as a solvent. In Excess and Citric Acid with Ethanol-90 as Solvent titration of synthesized trisodium citrate solution was carried out with hydrochloric acid HCl-0.1N using a burette-50[ml] and a helianthine color indicator according to a method operative described below. This titration procedure allowed the evaluation of the molar conversion of citric acid. The total crystallization of the concentrated trisodium citrate being completed, the porosity of this crystal was determined by immersing 0.0174 [g] of dehydrated trisodium citrate crystals in 15 [ml] of absolute alcohol using a crystallizer covered with a bell jar and a beaker-250[ml] to avoid humid air condensation during 150[mn]
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