Potassium sulfate, crystallization

As an example of the variations in shape that can be exhibited by a single crystalline material, consider the forms of potassium sulfate shown in Fig. 8. Clearly, the processing characteristics and particulate properties of the differently shaped potassium sulfate crystals will vary. 

Rigterink and France,10 using potassium sulfate crystals, found the basic structure of the dye influenced the adsorption. Dyes with the nucleus... 

Basicity chrome alum CCRIS 7532 Chrome alum Chrome potash alum Chromic potassium sulfate Chromic potassium sulphate Chromium potassium bis(sulphate) Chromium potassium sulfate (1 1 2) Chromium potassium sulfate (CrK(S04)2) Chromium potassium sulphate Chromium(lll) potassium sulfate Crystal Chrome Alum EINECS 233401-6 Potassium chromic sulfate Potassium chromic sulphate Potassium chromium alum Potassium chromium disulfate (KCr(S04)2) Potassium disulphatochromate (III) Sulfuric acid, chromium(3 ) potassium salt (2 1 1). Mordant for dyeing fabrics uniformly [dodecahydratej mp = 89° d = 1.83 soluble in 4 parts H2O. 

A batch evaporative crystallizer (Figure 10.2) was used by Baliga (1970) to study the crystallization kinetics of potassium sulfate crystals. The crystallizer was equipped with a reflux condenser and a controlled distillate splitter so that the net solvent removal rate could be controlled closely. Heating of the crystallizer... 

Fig. 4 Normalized growth length of potassium sulfate crystal as a function of time...

Figure 9.13 shows a quintuple-effect evaporation crystallisation plant for the concentration of Yeast Vinasse and recovery of Potassium sulfate crystals in Hungary. 

NiSO (NH 2 04-6H20, and nickel potassium sulfate [10294-65-2], NiSO -K2S04-6H20, are prepared by crystallizing the individual salts from a water solution. These have limited use as dye mordants and are used in metal-finishing compositions (59). 

In Canada, ion-exchange (qv) technology has been used to produce potassium sulfate (4). Ion-exchange resins remove sulfate ions from lake water containing sodium sulfate. This is followed by a wash with aqueous solutions prepared from lower grade muriate of potash. High purity potassium sulfate is collected from the crystallizers into which the wash mns. 

Potassium and ammonium dichromates are generally made from sodium dichromate by a crystallization process involving equivalent amounts of potassium chloride or ammonium sulfate. In each case the solubiHty relationships are favorable so that the desired dichromate can be separated on cooling, whereas the sodium chloride or sulfate crystallizes out on boiling. For certain uses, ammonium dichromate, which is low in alkaH salts, is required. This special salt may be prepared by the addition of ammonia to an aqueous solution of chromic acid. Ammonium dichromate must be dried with care, because decomposition starts at 185°C and becomes violent and self-sustaining at slightly higher temperatures. 

Potassium sulfate has a solubility of 15 g/100 g water at 40°C. A solution is prepared by adding 39.0 g of potassium sulfate to 225 g of water, carefully heating the solution, and cooling it to 40°C. A homogeneous solution is obtained. Is this solution saturated, unsaturated, or supersaturated The beaker is shaken, and precipitation occurs. How many grams of potassium sulfate would you expect to crystallize out ... 

A well-mixed continuous crystallizer is to be used to separate potassium sulfate from an aqueous solution by cooling crystallization. The solubility of potassium sulfate can be represented by the expression ... 

Figure 4. Helix axis projection of the chondroitin 4-sulfate crystal structure. Molecules with full and open bonds indicate up- and down-pointing chains. The large and small filled circles represent potassium ions and water molecules respectively. (Reproduced with permission from ref. 18. Copyright 1983 Academic Press Inc.)...

Potassium sulfate is separated from the more soluble magnesium chloride by crystallization. 

Rubidium is recovered from its ore lepidolite or pollucite. Mineral lepidolite is a lithium mica having a composition KRbLi(OH,F)Al2Si30io. The ore is opened by fusion with gypsum (potassium sulfate) or with a mixture of barium sulfate and barium carbonate. The fused mass is extracted with hot water to leach out water-soluble alums of cesium, rubidium, and potassium. The solution is filtered to remove insoluble residues. Alums of alkali metals are separated from solution by fractional crystallization. Solubility of rubidium alum or rubidium aluminum sulfate dodecahydrate, RbAl(S04)2 I2H2O falls between potassium and cesium alum. 

Scandium salts are colorless, and give gelatinous precipitates with potassium hydroxide and sodium carbonate. The sulfate crystallizes with difficulty. 

The tables of solubility show that at 20° about 11 g. of potassium sulfate dissolves in 100 g. of water, while at 100° about 24 g. dissolves. Crystals will therefore form rather slowly from a cooling saturated solution. 

As a preliminary, ferric sulfate is made by the oxidation of ferrous sulfate. Dissolve 100 g. of ferrous sulfate in 100 cc. of boiling water, to which has been added before heating 10 cc. of sulfuric acid. Add concentrated nitric acid portionwise to the hot solution, until a diluted sample gives a reddish-brown (not black) precipitate with ammonia. This will require about 25 cc. Boil the solution down to a viscous liquid to get rid of excess nitric acid, dilute to about 400 cc., and add the calculated weight of ammonium sulfate. The crystallization is conducted as in the former exercise, preferably under 20°. By the addition of potassium sulfate, the corresponding potassium iron alum may be secured. In this case, it is necessary to concentrate the solution until there is about four parts of water to one of the hydrated alum and cool to about zero to secure crystallization. Both of these alums are amethyst in color, the potassium salt being much less stable and having a rather low transition point. 

Two tilings about aluminum will interest you as a chemist. One is that aluminum is an "amphoteric element, which means that it can form not only a base (Al(OH)j). hut also an acid (HA 10,). The other is that aluminum sulfate (Al SO, ) has the ability to combine with potassium sulfate (K,SO ) and ammonium sulfate ((NHJjSO,) into beautiful cubic crystals of double salts called alums — KA1 (S04)3 12H,0 and NH4A1(S04),-12H,0. 

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