Neutralizing chlorinated water
It is used to dechlorinate tap water including lowering chlorine levels for use in aquariums, swimming pools, and spas (e.g., following superchlorination) and within water treatment plants to treat settled backwash water prior to release into rivers. The reduction reaction is analogous to the iodine reduction reaction. In pH testing of bleach substances, sodium thiosulfate neutralizes the color-removing effects of bleach and allows one to test the pH of bleach solutions with liquid indicators. The relevant reaction is akin to the iodine reaction: thiosulfate reduces the hypochlorite (active ingredient in bleach) and in so doing becomes oxidized to sulfate. The complete reaction is:

4 NaClO + Na2S2O3 + 2 NaOH → 4 NaCl + 2 Na2SO4 + H2OSimilarly, sodium thiosulfate reacts with bromine, removing the free bromine from solution. Solutions of sodium thiosulfate are commonly used as a precaution in chemistry laboratories when working with bromine and for the safe disposal of bromine, iodine, or other strong oxidizers. Structure
Two polymorphs are known of the pentahydrate. The anhydrous salt exists in several polymorphs. In the solid state, the thiosulfate anion is tetrahedral in shape and is notionally derived by replacing one of the oxygen atoms by a sulfur atom in a sulfate anion. The S-S distance indicates a single bond, implying that the terminal sulfur holds a significant negative charge and the S-O interactions have more double-bond character.
Psychasthenia was a psychological disorder characterized by phobias, obsessions, compulsions, or excessive anxiety. The term is no longer in psychiatric diagnostic use, although it still forms one of the ten clinical subscales of the popular self-report personality inventories MMPI and MMPI-2. Signs and symptoms
The MMPI subscale 7 describes psychasthenia as akin to obsessive-compulsive disorder, and as characterised by excessive doubts, compulsions, obsessions, and unreasonable fears. The psychasthenic has an inability to resist specific actions or thoughts, regardless of their maladaptive nature. In addition to obsessive-compulsive features, the scale taps abnormal fears, self-criticism, difficulties in concentration, and guilt feelings. The scale assesses long-term (trait) anxiety, although it is somewhat responsive to situational stress as well. The psychasthenic has insufficient control over their conscious thinking and memory, sometimes wandering aimlessly and/or forgetting what they were doing. Thoughts can be scattered and take significant effort to organize, often resulting in sentences that do not come out as intended, therefore making little sense to others. The constant mental effort and characteristic insomnia induces fatigue, which worsens the condition. Symptoms can possibly be greatly reduced with concentration exercises and therapy, depending on whether the condition is psychological or biological. History
The term "psychasthenia" is historically associated primarily with the work of Pierre Janet, who divided the neuroses into the psychasthenias and the hysterias, discarding the term "neurasthenia" since it implied a neurological theory where none existed.