Sulphur thiocyanate

Sulphur Thiocyanate, S(SCN)2, is formed as colourless, pearly crystals, when a solution of thiocyanogen in ether reacts with dry hydrogen sulphide. It decomposes at atmospheric temperatures. Heated in an open tube on a water-bath it darkens rapidly and then suddenly decomposes, evolving orange fumes. A solution of sulphur thiocyanate in a mixture of ether and benzene does not react with powdered iron, but on the addition of a drop of water the characteristic red colour of ferric thiocyanate develops immediately. By this reaction sulphur thiocyanate can be distinguished from free thiocyanogen.2... 

Prussian blue, Turnbull s blue, or even the material used in gas purification, is added this contains free sulphur, thiocyanates, and complex metallic cyan ides. 

It is essential to use an excess of sodium, otherwise if sulphur and nitrogen are both present sodium thiocyanate, NaCNS, may be produced in the test for nitrogen it may give a red coloration with ferric iron but no Prussian blue since there will be no free cyanide ions. With excess of sodium the thiocyanate, if formed, will be decomposed ... 

Sinapine, CjgHjjOgN, was isolated as a thiocyanate from black mustard seeds (Brassica nigra) by Henry and Garot." Will and Laubenheimer first noted that sinapine occurs in white mustard seed in the form of the alkaloidal glucoside sinalbine, CajH jOuNgSg, which, on hydrolysis by the enzyme myrosin, also present in the seed, furnished dextrose, p-hydroxybenzylthiocarbimide and sinapine sulphate. Owing to its instability sinapine is unknown in the free state. The thiocyanate can be recrystallised from water and converted into the acid sulphate by treatment with sulphuric acid. 

Estimation The above medium is reinforced with lOg/i of thiocyanate, sulphur is omitted and it is prepared as pour plates by the addition of 3% agar. Organisms other than Thiobacilli will grow from spread samples, but the Thiobacilli are easily distinguished by sulphur haloes (see Fig. 2.19). 

To limit the total porosity of the coating, checking by the Iron Solution Value (ISV) test in which samples are immersed under standard conditions in a solution of sulphuric acid, hydrogen peroxide and ammonium thiocyanate, and the amount of iron dissolved is measured... 

In nitrogenous fertiliser solutions of the NH4NOJ—NHj —HjO type corrosion of steel can be prevented by 500 p.p.m. of sulphur-containing inhibitors, e.g. mercaptobenzothiazole, thiourea and ammonium thiocyanate. However, these inhibitors are not so effective where most of the NHj is replaced by urea. For these solutions phosphate inhibitors such as (NH4>2HP04 and polyphosphates were more effective... 

The precipitate is curdy (compare silver chloride) and is readily coagulated by boiling. It is washed with dilute ammonium thiocyanate solution a little sulphurous acid or ammonium hydrogensulphite is added to the wash solution to prevent any oxidation of the copper)I) salt. 

Determination of nitrate as nitron nitrate Discussion. The mono-acid base nitron, C20H16N4, forms a fairly insoluble crystalline nitrate, C20H 16N4,HN03 (solubility is 0.099 g L 1 at about 20 °C), which can be used for the quantitative determination of nitrates [see Section 11.11(E)]. The sulphate and acetate are soluble so that precipitation may be made in sulphuric or acetic (ethanoic) acid solution. Perchlorates (0.08 g), iodides (0.17 g), thiocyanates (0.4 g), chromates (0.6 g), chlorates (1.2g), nitrites (1.9 g), bromides (6.1 g), hexacyanoferrate(II), hexacyanoferrate(III), oxalates, and considerable quantities of chlorides interfere, and should be absent. The figures in parentheses are the approximate solubilities of the nitron salts in g L-1 at about 20 °C. 

Determination as copper (I) thiocyanate, CuSCN. The solution (100 mL) should be neutral or slightly acid (hydrochloric or sulphuric acid), and contain not more than 0.1 g SCN . It is saturated with sulphur dioxide in the cold (or 50 mL of freshly prepared saturated sulphurous acid solution added), and then treated dropwise and with constant stirring with about 60 mL of 0.1M copper sulphate solution. The mixture is again saturated with sulphur dioxide (or 10 mL of... 

A definite nitrido coordination chemistry has grown up including abstraction of sulphur from thiocyanate (Figure 1.74). 

In many cases, it has been found that 7r-bonding ligands favour S-bonding. In a complex with both N- and S-bonded thiocyanate (Figure 3.74) the N-bonded group is trans to P while the sulphur-bonded thiocyanate is trans to the harder nitrogen ( anti-symbiosis ). 

Subsequently it was shown that the P-Pd-P angles were essentially the same as in the corresponding chloride complexes (section 3.8.3) as a result, as the P—Pd—P angle increases, concomitant upon the increase in the length of the methylene chain, steric effects enforce N-bonded thiocyanate, which is less sterically demanding that the non-linear Pd-SCN linkage (favoured on HSAB considerations since Pd2+ is a soft acid and sulphur is a soft base). 

The thiocyanate K2[Pt(SCN)6].2H20 contains octahedrally coordinated platinum, confirming the readiness of platinum(IV) to bind to a soft donor atom like sulphur [182]. 

These and similar results can be explained if the simultaneous reduction of hydrogen peroxide is due to an induced reaction. To show the characteristic features of this reaction some results are presented in Table 19 and Table 20. The procedure for these measurements was as follows. The solution of peroxy compounds given in columns 1 and 2 was made up to 20 ml and the pH was adjusted to the given value. Then potassium thiocyanate solution was added and, after the reaction time noted, the process was quenched by adding potassium iodide solution (0.3 g KI). After 5 sec the solution was acidified with 1 ml 2 iV sulphuric acid then using, molybdate catalyst solution, the iodine liberated was titrated with standard thiosulphate. 

The reaction between peroxysulphuric acid and thiocyanate ions was investigated by Smith and Wilson by a stopped-flow conductance method. Their results can be summarized as follows. If / and m are the numbers of moles of cyanate and sulphur dicyanide produced per mole of thiocyanate consumed, the overall stoichiometric equation is... 

Oh, S.Y., S. Jalaludin, R.H. Davis, and A.H. Sykes. 1987. Detoxication of cyanide in the chicken by conversion to thiocyanate, as influenced by the availability of transferable sulphur. Comp. Biochem. Physiol. 86B 129-133. 

In addition to benzenoid diazo components, diazotised heterocyclic amines in which the amino group is attached to a nitrogen- or sulphur-containing ring figure prominently in the preparation of disperse dyes [87,88], since these can produce marked bathochromic shifts. The most commonly used of these are the 6-substituted 2-aminobenzothiazoles, prepared by the reaction of a suitable arylamine with bromine and potassium thiocyanate (Scheme 4.31). Intermediates of this type, such as the 6-nitro derivative (4.79), are the source of red dyes, as in Cl Disperse Red 145 (4.80). It has been found that dichloroacetic acid is an effective solvent for the diazotisation of 2-amino-6-nitrobenzothiazole [89]. Subsequent coupling reactions can be carried out in the same solvent system. Monoazo disperse dyes have also been synthesised from other isomeric nitro derivatives of 2-aminobenzothiazole [90]. Various dichloronitro derivatives of this amine can be used to generate reddish blue dyes for polyester [91]. 

Among phosphorus insecticides containing also nitrogen and sulphur we may mention 00 -diethyl-/S-/ -diethylaminoethyl phosphorothiolate (X). It was prepared (i) from diethyl phos-phorochloridate1 and sodium / -diethylaminoethyl mercaptide, (ii) from sodium diethyl phosphite and / -diethylaminoethyl thiocyanate, (iii) by the isomerization of OO -diethyl-O"-/ -diethylaminoethyl phosphorothionate (XI) obtained from / -diethylaminoethoxide and diethyl phosphorochloridothionate. 

Materials Required Ethionamide 0.3 g dilute sulphuric acid (10% w/w) 10 ml dilute ammonia solution (4.25 ml of strong ammonia solution in 100 ml of water) 0.1 N silver nitrate 50 ml dilute nitric acid (10.6 ml of nitric acid to 100 ml of water) 60 ml ferric ammonium sulphate solution (10% w/v in water) 5 ml and 0.1 N ammonium thiocyanate solution. 

Procedure Weigh accurately about 0.3 g of ethionamide in a flask and dissolve in 10 ml of dilute sulphuric acid. Add to it 100 ml of water, 20 ml of dilute ammonia solution and rapidly 50 ml of 0.1 N silver nitrate solution. Allow the resulting mixture to stand for a few minutes, filter and wash the filter paper with three successive quantities, each of 10 ml of DW. To the combined filtrate and washings, add 60 ml of dilute nitric acid, cool and titrate with 0.1 N ammonium thiocyanate employing 5 ml of ferric ammonium sulphate solution as an indicator. Each ml of 0.1 N silver nitrate is equivalent to 0.008312 g of C8H1QN2S. 

---