Perchlorate gravimetric analysis

Tetraphenylarsonium chloride (107,108) has also been used for the precipitation of the perchlorate ion in gravimetric analysis. 

Properties. The Qf of the anhyd salt was calcd to be — 179kcal/mole (Ref 8), and of the aq soln to be — 173.94kcal/mole (Ref 6). Effect of heat Marvin Woolaver found by thermo-gravimetric analysis that Ca perchlorate starts to decomp at 220° and decomps rapidly at 400° to give Ca oxide, Ca chloride, and perchloric ac (Ref 5). Chudinov in the USSR states thatit decomps betw 320 and 455° with the formn of Ca oxide, Ca chloride, Cl, and O (Ref 7). Solubility it is sol in w and most org solvs except eth (Ref 3)... 

The NaCl -SOD formed during these reactions can be clearly identified by its IR spectrum, perchlorate sodalite collapse at 1050°C. From the thermo gravimetric analysis it is evident that at this temperature the entire amount of NaCl escapes. The degree of the cage filling by salt molecules can be calculated on the basis of both the oxygen and the NaCl loss. 

Gilford and Taylor (Ref 59a) studied the W-Ba chromate-K perchlorate delay system using DTA, Expanded Thermal Gravimetric Analysis,... 

Yang and Chien [35] observed that the reaction of Shirakawa polyacetylene with perchlorate counter-ions can be explosive and that the perchlorate doped samples were more stable to oxygen than is the undoped material which is further supported by the work of Pochan el al. [83], Haq and Farrington [32] and Druy et al. [29] on iodine and perchlorate-doped Shirakawa polyacetylene. Aldissi [84] prepared polyacetylene by dissolving monomer and then exposing to AsF below -84"C. Thermo-gravimetric analysis of... 

In gravimetric analysis, the solution-preparation step has its own special significance. The analyte must be separated from interfering species, or the interferents must be masked. For example, if iron(III) is to be estimated as its hydrated oxide in the presence of chromium(III), then the mixture is initially treated with perchloric acid so as to oxidize chromium(III) to chromate (chromium(VI), Cr04 ), followed by addition of ammonia to precipitate the hydrated iron oxide. Sometimes it is necessary to remove interferents, for example, when calcium is to be estimated as calcium sulfate in the presence of barium. The barium is removed as its chromate and the calcium is precipitated quantitatively as its sulfate. 

Fluoride ion, and weak acids and bases do not interfere, but nitrate, nitrite, perchlorate, thiocyanate, chromate, chlorate, iodide, and bromide do. Since analysis of almost all boron-containing compounds requires a preliminary treatment which ultimately results in an aqueous boric acid sample, this procedure may be regarded as a gravimetric determination of boron. 

The gravimetric methods of analysis with perchlorate or tetraphenyl boro-sodium, frequently used in the past, are rarely used today. 

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