Thallous chloride , reaction

Reference Electrodes and Liquid Junctions. The electrical cincuit of the pH ceU is completed through a salt bridge that usually consists of a concentrated solution of potassium chloride [7447-40-7]. The solution makes contact at one end with the test solution and at the other with a reference electrode of constant potential. The Hquid junction is formed at the area of contact between the salt bridge and the test solution. The mercury—mercurous chloride electrode, the calomel electrode, provides a highly reproducible potential in the potassium chloride bridge solution and is the most widely used reference electrode. However, mercurous chloride is converted readily into mercuric ion and mercury when in contact with concentrated potassium chloride solutions above 80°C. This disproportionation reaction causes an unstable potential with calomel electrodes. Therefore, the silver—silver chloride electrode and the thallium amalgam—thallous chloride electrode often are preferred for measurements above 80°C. However, because silver chloride is relatively soluble in concentrated solutions of potassium chloride, the solution in the electrode chamber must be saturated with silver chloride. 

When a positive current is sent through the cell in the direction from left to right, thallium goes into solution at the chloride electrode, and a corresponding amount of thallous chloride is precipitated, while thallous thiocyanate is decomposed and a corresponding amount of metallic thallium is deposited at the other electrode. The reaction in the cell may therefore be represented by the equation... 

Acetate ion, however, complexes thallic ion about as well as chloride, and with aqueous thallic acetate there is not the complication of thalhc- and thallous-containing species precipitating as the reaction proceeds. Thallic acetate itself is unreactive towards ethylene, but if strong acid is added to the solution, the oxidation rate of ethylene increases. The values of K3 and K4 for the equilibria represented by Reactions 28 and 29 were determined by pH measurements (23). 

Thallium triacetate, 406 Thallous carboxylates, 410 Thallous ethoxide, 407-411 Thebaine, 330, 331 Thiacyclohexane, 358 Thiazolidine-4-carboxylic acid, 27 Thiele reaction, 7-9, 12, 13 Thiepin-1,1-dioxide, 392 Thioanisole, 99, 311, 324 Thiocarbonates, 105, 106 N,N -Thiocarbonyldiimidazole, 411-412 Thiocyanogen, 105, 440 Thionyl chloride, 176, 395, 410, 412 Thiophenols, 173, 174 Thiophosgene, 412 Thiourea, 157, 412-413 Thymidine, 297, 298 Thymidine 5 -phosphate, 298 Thymine, 370 Tigonin, 136 Tin, 414... 

Reaction of Thallous Selenide and Bis(organoseleno)mercury with Acid Chlorides... 

To detect manganese in the presence of silver and thallium, the latter are best precipitated as chlorides, the precipitate removed by filtering or centrifuging, and the test carried out on the clear liquid. Thallic salts can be reduced to thallous sulfate with sulfur dioxide, and then precipitated with sodium chloride. The sensitivity of the test remains the same as for pure manganese salts. The silver and thallium must be removed before carrying out the test since addition of alkali to a solution containing these ions gives the reaction ... 

Thioesters, Selenoesters, and Thioamides.—Commercially available phenyl dichlorophosphate has been reported to be a superior reagent to MV-dimethyl-phosphoramidic dichloride (4, 244) for the preparation of thioesters directly from carboxylic acids and thiols. Carboxylic acid chlorides can be efficiently converted into thioesters by reaction with adducts formed between thiols and l-methylpyridine-3,5-dicarboxylates. Alternatively, copper(i) mercaptides, formed from thiols and CuaO, or thallous thiophenoxide can be used. The latter method can also be used to prepare selenoesters as well as a-phenylthio-and a-phenylseleno-acids and esters from a-halo-acids and a-halo-esters, respectively. 

Thallous ethoxide added all at once with stirring to 1.1 moles acetylacetone in petroleum ether, stirring continued 2-3 min., chilled and filtered acetylaceto-natothallium(I) (Y ca. 100%) suspended in methyl iodide, stirred and refluxed 4 hrs. -> 3-methylpentane-2,4-dione (Y ca. 100%). - This synthesis proceeds cleanly without any side reactions. F. e., also G-acetylation with acetyl fluoride and 0-acelylation with acetyl chloride, s. E. C. Taylor, G. H. Hawks, III, and A. McKillop, Am. Soc. 90, 2421 (1968). 

---