Ammonium selenates

The uncertainty added by the review corresponds to an uncertainty in the mean activity coefficient of 5%. 

Selivanova, Prymova, and Kravchenko [71SEL/PRY] measured the enthalpy change of the reaction (NH4)2Se04(cr) + Pb(N03)2(aq, 1 1600) PbSe04(cr) + 2NH4N03(aq, 1 800) and the enthalpy of dissolution of (NH4)2Se04(cr) to (NH4)2Se04(aq, 1 1600) in a calorimeter. The review has recalculated the data to standard conditions and obtained for  

The standard enthalpy of formation of (NH4)2Se04(cr) found from the enthalpies of reaction and selected enthalpies of formation is - (878.41 4.62) and - (878.50 3.57) kJ moP, respectively. The average will be selected  

The standard Gibbs energy of formation of ammonium selenate is calculated from the Gibbs energy of Reaction (V. 185) and the selected values of Af G° for the ions to be  

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Ammonium selenate [7783-21-3] M 179.0, d 2.19, m dec on heating. Crystd from water at room temperature by adding EtOH and cooling. 

The similarity to tellurium has given me occasion to name the new substance selenium.. .. In the hope of pleasing you and Mr. Wollaston, I am enclosing a little thread of selenium, which will surely be broken before arriving, but some of it will always remain. The paper in which it is wrapped has been colored by a sublimation of selenium which took place when, in my absence, the fire was stirred up too much in order to evaporate a solution of ammonium selenate (8). 

Ammonium selenates.—On evaporation, a solution of selenic acid saturated with ammonia yields the normal selenate, (NH4)2Se04, in monoclinic 7 crystals. At 7° C. its solubility is 117 grams in 100 grams of water.8 When gently heated, the normal salt is converted into ammonium hydrogen selenate, NH4HSe04,9 of density 2 162.10... 

The dissolution data were evaluated on the assumption that the enthalpy of dilution of the ammonium selenate solution was the same as for the corresponding sulphate solution with data from [82WAG/EVA]. 

SEL/PRY] Selivanova, N. M., Prymova, L. A., Kravchenko, L. K., Physicochemical study of ammonium selenate, Izv. Vyssh. Uchebn. Zaved., Khim. Khim. Tekhnol, 14, (1971), 647-650, in Russian. Cited on pages 411, 531. 

HAV/M1C] Havlicek, D., Micka, Z., Boublikova, R., Lithium and ammonium selenates. Collect. Czech. Chem. Commun., 60, (1995), 969-976. Cited on pages 411,415. 

Grafting of methyl methacrylate on starch occurs in an aqueous, saturated starch solution at 85 °C in the presence of carbon tetrachloride or copper(II) ions,2808,2809 and the grafting efficiency could be as high as 72%. At a low concentrations of the vinyl compound, the reaction rate was proportional to its concentration. The reaction rate became independent of concentration at higher concentrations of the vinyl monomer. Grafting in the presence of 0.1M nitric acid and ammonium selenate was also reported.2810... 

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