Thionic acids

In addition to the simple acids discussed above, sulphur forms two peroxosulphuric acids containing the —O—O— linkage and a number of thionic acids containing more than one sulphur atom. 

Further reaction between hydrogen sulphide and the sulphite ion yields sulphur together with thionic acids) ... 

The equiHbrium constant is 0.013 at 18°C. Sulfur dichloride reacts violently with water, forming hydrogen chloride, sulfur dioxide, hydrogen sulfide, sulfur, and a mixture of thionic acids. 

Thion-kohlensaure, /. thionocarbonic acid, -kohlenthiolsaure, /. thiolthionocarbonic acid (HOCSSH). -saure,/. thionic acid. 

This salt, when decomposed by sulphuric acid, yields tetra-thionic arid. 

Salts of Thionic Acids.—A third class of thio salts are those derived from the various thionic acids of which sodium thiosulfate and barium dithionate may be... 

Hydrogen sulphide is the weakest acid, di- and tri-thionic acids are approximately of equal strength, whilst sulphurous acid is the weakest oxyacid in the list.1... 

Properties.—Like the lower members of the series of thionic acids, free pentathionic acid is known only in aqueous solution a solution of the pure acid is obtained by treating an aqueous solution of the potassium salt with the requisite quantity of tartaric acid for the removal of the potassium in the form of hydrogen tartrate. The solution is denser than water 4 it cannot be concentrated beyond a limit of 50 to 60 per cent, acid without decomposition. 

With water, the dichloride forms sulfuric acid, sulfur, and a mixture of thionic adds, HaSxO. It dissolves without reaction in hexane, carbon tetrachloride, carbon disulfide, and ethylene dichloride. 

The acids themselves have never been isolated, but salts of each have been prepared. Higher polythionates having chains of five or six sulfur atoms per molecule have been made. Tetrathionate, the most important thionic acid anion, results from the oxidation of S2OI with I2. Salts of the remaining thionic acids must be prepared by special methods. 

Dithionic acid appears in a solution of sulphurous acid oxidised by finely divided MnOg. From this, baryta precipitates all the sulphur-containing anions except dithionate, and, when the excess of Ba + has been precipitated by H2SO4, only 112820 is left in the solution. Although conductance measurements show the acid to be dibasic, acid salts are unknown. Dithionates are soluble in water and, unlike salts of the higher thionic acids, are not decomposed by sulphites and sulphides. 

As in the formazans of the simple sugars (15), those of the ozone-oxidized polysaccharides undergo reductive disintegration by the action of hydrogen sulfide. Thus, the formazan of ozone-oxidized starch gives the corresponding thionic acid phenyl-hydrazide. 

Thiolic acid A compound of the general type RC(=0)SH. See also thionic acid. 

Reductive decomposition of the formazans of oxidized polysaccharides, by means of hydrogen sulfide, as with the simple sugar formazans, yields sulfur-containing, nitrogenous polysaccharide derivatives which contain thionic acid phenylhydrazide groups. For example, when a pyridine-ethanol solution of oxy-starch formazan or oxy-dextrin formazan is saturated with hydrogen sulfide, the vividly red solution turns colorless and a yellow precipitate, which gives the Wuyts reaction characteristic of the thionic acid phenylhydrazides, separates. 

Thionic Acid Phenylhydrazide Derivatives from Oxidized Polysaccharides... 

Thionic acid phenyldrazide derivatives Appearance References... 

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