Sodium thiosulfate solutions applications

Iodide ion, a moderately effective reducing agent, is used extensively for the determination of oxidants. In such applications, the iodine liberated by reaction between the analyte and the unmeasured excess of potassium iodide is ordinarily titrated with a standard solution of sodium thiosulfate. The reaction is as follows ... 

Phenylarsine oxide, C6H5As = O, is as effective as sodium thiosulfate in reducing iodine. It is more stable than thiosulfate. An advantage is that it is stable even in dilute solution. This substance is, however, highly toxic and is a suspected carcinogen. Because of its toxicity, its application is limited. One such application is in the amperometric titration of residual chlorine. The oxidation-reduction reaction of PAO is similar to thiosulfate. Its equivalent weight in iodine reaction is 168. 

Chloramines can be removed from solution using carbon filtration, as noted in Chapter 8.1.4. However, the contact time for removal is about 4 times that of free chlorine. Chloramines can also be removed using sodium thiosulfate or bisulfite, and the reaction is fairly instantaneous. Note that with the carbon filtration removal method, some ammonia is created, which is toxic and should be considered when using an RO with chloramines for food processing and pharmaceutical applications (see Equation 8.2). However, as free chlorine is removed using sodium bisulfite, the chlorine-chloramine equilibrium can shift back to creating more free chlorine. In this case, complete removal of free chlorine cannot be assured. Carbon filters may be the best method to remove chloramines, but can take up to 30 minutes of residence time for complete reaction with the carbon. Ultraviolet radiation can also be used to destroy chloramines (see Chapter 8.1.8). 

Iodide ion is a moderately effective reducing agent. In its applications, a standard solution of sodium thiosulfate is used to titrate the iodine liberated by reaction of the analyte with an unmeasured excess of potassium iodide. Some substances determined by using iodo-metric method are 104 , lOs", BrOs, ClOs, Br2, CI2, O2, O3, Cu " ", N02, and organic peroxide. 

Applications Sodium sulfite is utilized as a reducing agent, in the manufacture of sodium thiosulfate, as an oxidation-prevention agent for developer solutions in the photographic industry, as an antichlorination agent in the paper and textile industries, for the preservation of food and for the treatment of boiler water. 

It is important that the agent be washed from the skin with soap and water as soon after exposure as possible. The eyes should be thoroughly flushed. The onset of symptoms typically is delayed and an absence of immediate effect does not rule out toxicity. Although ingestion is unlikely, due to the sources of mustard gas, an emetic should not be administered because of the extreme caustic nature of the chemical. If the patient is not comatose, dilution of stomach contents with milk or water, prior to gastric lavage, may be attempted. Application of a solution of sodium thiosulfate to the skin and inhalation of a nebulizing mist of sodium thiosulfate may speed inactivation of mustard gas. Animal studies have shown that administration of corticosteroids (e.g., dexamethasone) and antihistamines (e.g., promethazine) may prove beneficial. 

Carrier-free iodine-125 for protein iodination is available from different manufacturers in an aqueous solution containing sodium hydroxide or sodium sulfite with the activity claimed to be in the form of iodide. This may be true of freshly prepared solutions but in the course of a few weeks significant amounts of this iodide activity is transformed into unidentified species. These species may be volatile and do not exchange with added iodide even after the addition of sodium sulfite or sodium thiosulfate. The uncertainty of the chemical properties of these species essentially eliminates the direct application of chemical methods for analysis (27). Inasmuch as iodine-125 is produced by neutron-irradiation of xenon the isotopic impurities are limited to iodine-126 and iodine-127. It turns out that the total amount of iodine in an iodine-125 solution is represented primarily by iodine-125 and iodine-127 with only a negligible amount contriuted by iodine-126. The nuclides iodine-125 and iodine-127 were determined by measuring the iodine-126 and iodine-128 formed by thermal neutron activation of a sample. 

These properties have spurred our efforts to study and develop diamond electrodes for application as amperometric detectors for industrially important compounds, for example, sodium thiosulfate and naproxen. Additionally, a novel method of detecting nickel ions in electroless deposition solutions using diamond electrodes will also be reported. Finally, the electrocatalytic activity of gold nanoparticles deposited on diamond for oxygen reduction will be evaluated. 

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