Iodides using adsorption indicators

Titration methods using adsorption indicators, based on the precipitation of insoluble iodides, have also been proposed (81—84). The sensitivity of these methods is less than that for the thiosulfate titration. Electrometric titration of the reaction between iodine and thiosulfate (85) was not found to be practicable for routine deterrninations of minute quantities of iodine. 

Thus an almost complete separation is theoretically possible. The separation is feasible in practice if the point at which the iodide precipitation is complete can be detected. This may be done (a) by the use of an adsorption indicator (see Section 10.75(c)), or (b) by a potentiometric method with a silver electrode (see Chapter 15). 

Talc will adsorb the iodohormone, and it has been used in RIA to separate bound from free hormone and to purify iodohormones.Hormonal aggregates will easily dissociate from talc, and thus more than 90% of the labeled hormone should remain adsorbed to talc. Less than 90% talc adsorption indicates the formation of either free iodide or basic aggregates. Since acidic aggregates also may adsorb to talc, the talc and TCA percentages should agree within 3%. 

USE As an adsorption indicator in the determn of iodides in the presence of chlorides and bromides. The salts in dyeing and printing cotton, in printing half -silk, in dyeing jute, straw, etc,... 

Chang et al. [71] have studied adsorption of iodine, iodobenzene, iodoheptane, and l,4-dihydroxy-2-iodobenzene on Au(lll) electrode from 0.1 M HCIO4 solutions using CV and STM. The results obtained indicate that organic iodide molecules are significantly decomposed upon their adsorption to give an iodine layer and alkyl... 

The last step (which also may precede the previous one) is to determine the area A. This also is not always obvious. One choice is the BET-area (chapter 1) but a method based on adsorption from solution (chapter 2) may be more appropriate. In a number of cases, however, it was found that charge-determining ions "see" an area that differs from that obtained from adsorption of uncharged compounds. Silver iodide is a notorious example, to which we shall return in sec. 3.10a. In fact, any time that an example of a° is given, the area used to obtain the data set should be indicated. 

This work intends to show the complexity of the dynamic adsorption process and to evaluate capacity of some granular carbons of various firms to remove pollutants from water. Adsorbents have been tested by various methods, and static and dynamic adsorption have been compared. Characteristics of carbons has been evaluated by the determination of porous structure, specific surface, content of ashes (mineral substances) and crushing strength and abrasion resistance. Adsorption capacity of activated carbon has been determined by means of phenol, iodide, methylene blue, sodium lauryl sulphate and molasses indicators for static conditions, and surfactant has been used for dynamic conditions. Analysis of some factors influencing adsorption has been accomplished and directions of further studies have been shown. 

Fig. 10.26 Plots of experimental data for the adsorption of iodide ion on Hg according to the virial isotherm using data obtained from solutions of varying ionic strength [46]. The iodide ion activity was set equal to the mean ionic activity. The electrode charge density in xC cm is indicated adjacent to each plot.

Table 1. It was clearly indicated that MgO is preferable than Mg(OH)2 for iodine-adsorption, although surface area is also thought to be important. These results also suggested that the adsorption is not simply physical but contains chemical process, as supported by chemical changes detected by XRD, from MgO to Mg(OH)2 in water. As Treushchenko et al. reported [1], iodide potentially was adsorbed onto Mg(OH)2 as Mg(I03)2, however, any oxidants such as H2O2 were not used in our experiments, without O2 in air.

---