Double-salt formation

If one of the salts forms a hydrate of composition D, then the diagram will have the appearance shown in Fig. 15.28(a). The interesting feature of this diagram is that if the state point lies in the triangle ADB, the system consists exclusively of the three solids, D, B, A. Under appropriate conditions, usually at a higher temperature, the anhydrous salt may make its appearance on the diagram as in Fig. 15.28(b). 

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Magnesium sulfate undergoes three important types of reactions in aqueous solutions double decomposition, double salt formation, and formation of oxysulfate cements. Many insoluble magnesium salts may be precipitated out by double decomposition reactions ... 

Case II. 0 ne Double Salt Forms.—Figure 19 represents the simplest case of double-salt formation in which only one double salt forms. On addition of B to a saturated solution of A, the latter salt separates as before, up to the point C. Here a double salt begins to crystallize out. On adding A to a saturated solution of B, the latter salt is deposited up to the point E, when the double salt again appears. If we start at any point of unsaturation in the area EOC, as at a, saturation will be reached on the line EC, which is the curve for the solubility of the double salt, and this salt will separate. Starting at any point in the area BOE, the compound B will first appear, followed by the double salt, while any point in the area AOC will first yield A and later the double salt. It will be seen that in this case the two salts do not need to be in equivalent ratio to produce the... 

We begin the quantitative discussion on the kinetics of double salt formation as shown in Figure 6-6a by introducing the familiar flux equations for charged particles and neglect the cross terms. The evaluation will be done with the assumption of a semiconducting spinel product (te, = 1). In this case, d /e = 0 in the product, or djue = F-dtp and dr/Az = d//A. Thus,... 

The foregoing concerned the formal kinetics of various situations of double salt, formation. The quantitative relations become more complicated if reactants and product exhibit a noticeable range of nonstoichiometry. If only the transport properties of the reaction product are of interest, it is advisable to start, the reaction not with pure reactants but with reactants which are already saturated with the com-... 

Keywords /ram-cinnamic acid, double salt formation, [2+2]photodimerization, truxillic acid, truxinic acid, cyclobutane... 

For conceptually similar approaches, see (a) Ito, Y. Borecka, B. Trotter, J. Scheffer, J. R. Control of Solid-State Photodimerization of fraws-Cinnamic Acid by Double Salt Formation with Diamines. Tetrahedron Lett. 1995, 36, 6083-6086 (b) Amirsakis, D. G. Garcia-Garibay, M. A. Rowan, S. J. Stoddart, J. F. White, A. J. P. Williams, D. J. Host-Guest Chemistry Aids and Abets a Stereospecific Photodimerization in the... 

FIGURE 7.1 Solubility phase diagrams of diastereoisomeric salts, (a) Ideal behavior (b) end solid-solution behavior (c) full solid-solution behavior and (d) double salt formation. 

Frequently deviations from this ideal behavior are observed—for instance, as a result of end or even full solid-solution behavior (Figures 7.1b and 7.1c) or double salt formation (Figure 7.Id). In the former situation repeated (or fractional) crystallization is needed to obtain a diastereoiso-merically pure salt, whereas in the latter it is virtually impossible to obtain a pure salt. In addition to these physical constraints, cost and availability play a determining role in the actual application of resolving agents on an industrial scale. 

Many similar sulfito complexes are known 300), e.g., NH4[CuS03], [NH4]4[Cu2(S03)3]-3H20, and [NH4]g[Cu(S03)g].H20, but in the sodium and potassium series double-salt formation is even more... 

In 1887 Remsen, in an effort to explain double salt formation, represented SbBrs-SKCl as shown below ... 

Double-salt Formation. This is an important class of solid reactions, including all the reactions of silicate chemistry, spinel formation, the formation of Ag Hgl, etc. These reactions may proceed by movement of one or more kinds of ions. In spinel formation only one kind of ion is normally mobile in the product lattice, and reaction occurs therefore at the phase boundary of the inactive oxide and the spinel. In the reaction between... 

Our strategy is based on crystalline double-salt formation with diamines, which are used as a supramolecular linker to connect two acid molecules in a... 

The System Sodium Chloride-Potassium Chloride— Water.— This may be taken as an illustration of a simple system in which there is no double-salt formation, and in which, at all temperatures above 0 , the salts crystallise anhydrous from solution. 

Ito. Y. Borecka. B. Trotter. J. Scheffer. J.R. Control of solid-state photodimerization of trans-cinnamic acid by double salt formation with diamines. Tetrahedron Lett. 1995. 36, 6083-6086. 

Scheme 7 Solid-state [2-1-2] photodimerization of trans-cinnamates via double salt formation.

Ito and coworkers, for example, have demonstrated that 1,2-diamines (e.g., cyclohexane-1,2-diamine) can be reacted with anthracene-9-propionic acid (9-ap) in a double salt formation to afford a solid that reacts to give a head-to-head photodimer in 55% yield. Dunels and coworkers have also demonstrated that the salt formed from 9- N,N-dimethylamino)anthracene (dmaa) and furan-2-carboxylic acid reacts to give the head-to-tail dimer in near quantitative yield. An unsymmetrical [4+4] cycloaddition has also been reported via salt formation involving dmaa and the diacid muco. The salt assembled with anthracene pairs arranged in a head-to-tail fashion with C=C bonds separated by 3.58 and 3.65 A (Figure 22). On UV irradiation, the head-to-tail photoadduct formed in quantitative yield. 

At room temperature, those soluble sulphates which could react with calcium sulphate to produce double salt were only Na2S04, K2SO4, Rb2S04, CS2SO4, and (NH4)2S04. The hydration excitation for anhydrous calcium sulphate of these sulphates depended on their concentration and the rate of double salt formation. Table 2 showed the effect of K-sulphate solution with certain concentrations on hydration of anhydrite, and Figure 4 showed the XRD patterns of their hydration products. 

When there is too much surplus malic acid in the initial must, part of the calcium carbonate added to the treated volume produces soluble calcium malate. At the time of final blending, the surplus calcium reacts with the tartaric acid of the untreated must. The deacidification thus occurs in two steps and acts essentially on the tartaric acid. The tartaric acid concentration therefore has to be adjusted in order to decrease malic acid concentrations substantially, by double salt formation (Usseglio-Tomasset and Bosia, 1992). This result can be obtained by using a mixture of calcium carbonate and calcium tartrate, also... 

Ito, Y., Borecka, B., Trotter, J., and Scheffer, J. R., Control of solid-state photodimerization of trans-cinnamic acid by double salt formation with diamines. Tetrahedron Lett., 36,6083-6086,1995. Ito, Y., Borecka, B., Olovsson, G., Trotter, J., and Scheffer, J. R., Control of the solid-state photodimerization of some derivatives and analogs of trans-cinnamic acid by ethylenediamine. Tetrahedron Lett., 36, 6087-6090,1995. 

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