Silver thiocyanate

Procedures for the corresponding cyanate compounds are described in synthesis 6. 

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Silver Thiocyanate. Silver thiocyanate, AgSCN, is formed by the reaction of stoichiometric amounts of silver ion and a soluble thiocyanate. 

Ana.lytica.1 Methods. Thiocyanate is quantitatively precipitated as silver thiocyanate, and thus can be conveniendy titrated with silver nitrate. In the presence of a ferric salt, a red-brown color, produced by the ferric thiocyanate compex, indicates the end point. 

Silber-rhodanid, n. silver thiocyanate, -solbe, /. Pharm.) colloid silver ointment, -salpeter, m. silver nitrate, -salz, n. silver salt, -sau, /. silver ingot, -scfaaum, m. silver in thin leaves, or an imitation of it. -scheidtmg, /. separation of silver silver refining, -schein,... 

Silver fluoborate, reaction with ethyl bromide in ether, 46, 114 Silver nitrate, complexing with phenyl-acetylene, 46, 40 Silver oxide, 46, 83 Silver thiocyanate, 45, 71 Sodium amide, in alkylation of ethyl phenylacetate w ith (2-bromo-ethyl)benzene, 47, 72 in condensation of 2,4-pentanedione and 1 bromobutane to give 2,4-nonanedione, 47, 92 Sodium 2 ammobenzenesulfinate, from reduction of 2 mtrobenzenesul-finic acid, 47, 5... 

When the excess of silver has reacted, the thiocyanate may react with the silver chloride, since silver thiocyanate is the less soluble salt, until the ratio [C1 ]/[SCN ] in the solution is 169 ... 

The freshly precipitated silver thiocyanate adsorbs silver ions, thereby causing a false end point which, however, disappears with vigorous shaking. 

Discussion. The chloride solution is treated with excess of standard silver nitrate solution, and the residual silver nitrate determined by titration with standard thiocyanate solution. Now silver chloride is more soluble than silver thiocyanate, and would react with the thiocyanate thus ... 

Bromides can also be determined by the Volhard method, but as silver bromide is less soluble than silver thiocyanate it is not necessary to filter off the silver bromide (compare chloride). The bromide solution is acidified with dilute nitric acid, an excess of standard 0.1M silver nitrate added, the mixture thoroughly shaken, and the residual silver nitrate determined with standard 0.1 M ammonium or potassium thiocyanate, using ammonium iron(III) sulphate as indicator. 

Iodides can also be determined by this method, and in this case too there is no need to filter off the silver halide, since silver iodide is very much less soluble than silver thiocyanate. In this determination the iodide solution must be very dilute in order to reduce adsorption effects. The dilute iodide solution (ca 300 mL), acidified with dilute nitric acid, is treated very slowly and with vigorous stirring or shaking with standard 0.1 M silver nitrate until the yellow precipitate coagulates and the supernatant liquid appears colourless. Silver nitrate is then present in excess. One millilitre of iron(III) indicator solution is added, and the residual silver nitrate is titrated with standard 0.1M ammonium or potassium thiocyanate. 

The synthesis of (V-heterocyclic isothiocyanates has been a difficult challenge due to their propensity to oligomerize by autocatalysis. In an attempt to alleviate this issue, silver thiocyanate was used in a novel synthesis of 4-quinolyl isothiocyantes <06TL2161>. Reaction of 4-chloroquinoline with silver thiocyanate in refluxing anhydrous toluene for 12 h results in the desired product in quantitative yields and excellent purity. 

Silver fluoborate, reaction with ethyl bromide in ether, 46, 114 Silver nitrate, complexing with phenyl-acetylene, 46, 40 Silver oxide, 46, 83 Silver thiocyanate, 46, 71 Sodio-2-formyl-6-methylcyclohexanone, 48,41... 

Silver tetrafluoroborate, 22 674, 23 715 Silver thiocyanate, 22 674 Silver thiosulfate, 22 674, 675 in floristry, 22 659, 669 wastewater treatment plants and, 22 683... 

Note Soon after the addition of ammonium thiocyanate a white precipitate of silver thiocyanate is formed first and then a reddish-brown colour appears that fades out completely upon shaking thereby leaving a white precipitate of silver thiocyanate. The end-point is indicated by the appearance of a permanent faint reddish brown colour that does not vanish upon shaking. 

Silicon tetraisothiocyanate is prepared from silicon tetrachloride and silver thiocyanate or, preferably, ammonium thiocyanate. The silicon tetraisothiocyanate used by the checkers was slightly yellow however, this did not affect the yield of product. 

Exposure of the silver chloride or bromide to light results in an increase in the nitrogen yield. This is to be expected, because the action of the light supplies nuclei for the catalyzed reaction. On the other hand, exposure of silver thiocyanate, which is relatively insensitive to the action of light, has little or no effect on the amount of nitrogen obtained on subsequent reduction with hydroxylamine. 

Nitrosyl chloride in carbon tetrachloride reacts with silver thiocyanate to form silver chloride and nitrosyl thiocyanate ... 

Reaction with silver isocyanate or silver thiocyanate yields phosphorus triisocyanate or phosphorus trithiocyanate ... 

The reactions of potassium thiocyanate in aqueous solution are essentially those of the thiocyanate anion. Its reaction with ferric ammonium sulfate, apphed in Volhard titration, results in the formation of ferric thiocyanate, Fe(SCN)3. Similarly, in titration against shver nitrate, it forms insoluble silver thiocyanate, AgSCN. 

Silver thiocyanate [1701-93-5] M 165.9, m 265°(dec), d 3.746. Digest the solid salt with aqueous NH4NCS, wash thoroughly with H2O and dry at 110° in the dark. Soluble in dilute aqueous NH3. Dissolve in strong aqueous NH4NCS solution, filter and dilute with large volume of H2O when the Ag salt separates. The solid is washed with H2O by decantation until free from NCS ions, collected, washed with H2O, EtOH and dried in an air oven at 120°. Alternatively dissolve in dilute aqueous NH3 and single crystals are formed by free evaporation of the solution in air. [7CS 836, 2405 1932 IR and Raman Acta Chem Scand 13 1607 1957 Acta Cryst 10 29 7957]. 

This compound is formed by the interaction of silver thiocyanate and cyanogen iodide in ether solution, silver iodide separating out 5... 

Silver thiocyanate, formed as a white, flocculent precipitate by double decomposition, is insoluble in dilute mineral acids. It is upon the formation of this salt that Volhard s volumetric method for the determination of silver or of thiocyanate (see p. 283) depends. 

Table 26 IR Data for Some Silver Thiocyanate Phosphine Complexes...

The crystal structures of two isomeric 15-membered ring macrocycles containing the donor groups ON2S2 (70) and OS2N2 (71) have been determined as their silver thiocyanate salts.468 469 In the first, the coordination sphere around the Ag1 ion embedded in the cavity was approximately square pyramidal, with a weak interaction between the Ag ion and the O atom (Ag—O 288.3 pm). In the second, a square pyramidal structure was again obtained, although in this case there was no interaction with the O atom (Ag—O 371.9 pm). 

Isomerization of organic thiocyanates to isothiocyanates is also discussed in other articles.25 29 The first sugar isothiocyanate reported, namely, 2,3,4,6-tetra-O-acetyl-/3- D-glucopyranosyl isothiocyanate (2) was synthesized by Emil Fischer7 in 1914 by treatment of 2,3,4,6-tetra-O-acetyl-a-D-glucopyranosyl bromide (1) with silver thiocyanate in anhydrous xylene. It was also prepared by Muller and Wilhelms8 by thermal isomerization of the corresponding thiocyanate 3, obtained by treatment of 1 with potassium... 

The Fischer method7 for preparation of sugar isothiocyanates is general however, many modifications have been introduced, using, for example, nonpolar solvents and silver thiocyanate,29 33 lead thiocyanate,33 or ammonium thiocyanate,34 and potassium thiocyanate in acetonitrile in the presence of tetrabutylammonium hydrogensulfate.34 ... 

Thiocyanic acid is formed by reaction of barium thiocyanate solution and dilute sulfuric acid, and filtering off barium sulfate, or by the action of hydrogen sulfide on silver thiocyanate, filtering off silver sulfide. 

Often, greater accuracy may be obtained, as in Volhard type titration, by performing a back titration of the excess silver ions. In such a case, a measured amount of standard silver nitrate solution is added in excess to a measured amount of sample. The excess Ag+ that remains after it reacts with the analyte is then measured by back titration with standard potassium thiocyanate (KSCN). If the silver salt of the analyte ion is more soluble than silver thiocyanate (AgSCN), the former should be filtered off from the solution. Otherwise, a low value error can occur due to overconsumption of thiocyanate ion. Thus, for the determination of ions (such as cyanide, carbonate, chromate, chloride, oxalate, phosphate, and sulfide, the silver salts of which are all more soluble than AgSCN), remove the silver salts before the back titration of excess Ag.+ On the other hand, such removal of silver salt is not necesary in the Volhard titration for ions such as bromide, iodide, cyanate, thiocyanate, and arsenate, because the silver salts of these ions are less soluble than AgSCN, and will not cause ary error. In the determination of chloride by Volhard titration, the solution should be made strongly acidic to prevent interference from carbonate, oxalate, and arsenate, while for bromide and iodide analysis titration is carried out in neutral media. 

In cold solution, yellow coloration is produced upon warming, violent reaction occurs and carbonyl sulfide is formed White precipitate of silver thiocyanate... 

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