If symptoms persisted after a few weeks at a local Casualty Clearing Station, which would normally be close enough to the front line to hear artillery fire, a casualty might be evacuated to one of four dedicated psychiatric centres which had been set up further behind the lines, and were labelled as "NYDN – Not Yet Diagnosed Nervous" pending further investigation by medical specialists. Although the Battle of Passchendaele generally became a byword for horror, the number of cases of shell shock were relatively few. 5,346 shell shock cases reached the Casualty Clearing Station, or roughly 1% of the British forces engaged. 3,963 (or just under 75%) of these men returned to active service without being referred to a hospital for specialist treatment. The number of shell shock cases reduced throughout the battle, and the epidemic of illness was ended.During 1917, "shell shock" was entirely banned as a diagnosis in the British Army, and mentions of it were censored, even in medical journals. Chronic treatment
The treatment of chronic shell shock varied widely according to the details of the symptoms, the views of the doctors involved, and other factors including the rank and class of the patient. There were so many officers and men with shell shock that 19 British military hospitals were wholly devoted to the treatment of cases. Ten years after the war, 65,000 veterans of the war were still receiving treatment for it in Britain. In France it was possible to visit aged shell shock victims in hospital in 1960.
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.