Ammonium sulfate, solubility

Ammonium sulfate [7783-20-2], (NH 2 U4, is a white, soluble, crystalline salt having a formula wt of 132.14. The crystals have a rhombic stmcture d is 1.769. An important factor in the crystallization of ammonium sulfate is the sensitivity of its crystal habit and size to the presence of other components in the crystallizing solution. If heated in a closed system ammonium sulfate melts at 513 2° C (14) if heated in an open system, the salt begins to decompose at 100°C, giving ammonia and ammonium bisulfate [7803-63-6], NH HSO, which melts at 146.9°C. Above 300°C, decomposition becomes more extensive giving sulfur dioxide, sulfur trioxide, water, and nitrogen, in addition to ammonia. 

The reactivity of titanium dioxide toward acid is dependent on the temperature to which it has been heated. Freshly precipitated titanium dioxide is soluble iu concentrated hydrochloric acid. However, titanium dioxide that has been heated to 900°C is almost iusoluble iu acids except hot concentrated sulfuric, iu which the solubiUty may be further iucreased by the addition of ammonium sulfate to raise the boiling poiut of the acid, and hydrofluoric acid. Similarly, titanium dioxide that has been calciued at 900°C is almost iusoluble iu aqueous alkahes but dissolves iu molten sodium or potassium hydroxide, carbouates, or borates. 

Ammonium cyanide may be prepared in solution by passing hydrogen cyanide into aqueous ammonia at low temperatures. It may also be prepared from barium cyanide and ammonium sulfate, or calcium cyanide with ammonium carbonate. It may be prepared in the dry state by gentiy heating a mixture of potassium cyanide or ferrocyanide and ammonium chloride, and condensing the vapor in a cooled receiver. Ammonium cyanide is soluble in water or alcohol. The vapor above soHd NH CN contains free NH and HCN, a very toxic mixture. 

The method of extraction of Ru(III) from thiocyanate solutions by water soluble extractants in the presence of ammonium sulfate as salting out agent followed by photometric determination of it in extract has been elaborated. 

S100 proteins (named because of their solubility in a 100% ammonium sulfate solution) constitute the largest family within the EF-hand Ca2+-binding proteins superfamily [1]. SI00 proteins are small, acidic proteins containing two distinct Ca2+-binding EF-hand structural motifs [2]. The C-terminal EF-hand contains the... 

Dilution of the methanesulfonic acid is exothermic. Since peroxybenzoic acid has an appreciable solubility in aqueous methanesulfonic acid, dilution and washing are conducted with minimal quantities of saturated ammonium sulfate solution. 

A pure complex between Hp and Hb was isolated by van Royen (R5), who utilized the observation of Jayle and Gillard (J10) that the solubility of the HpHb complex in ammonium sulfate is higher than that of Hp. All attempts to recover Hp from its Hb complex have hitherto failed. 

Solubility curves for different types of Hp have been presented (H5, H7). The higher solubility of type 1-1 than that of the others is in conformity with its lower molecular weight. The irregularity of the solubility curves for Hp of 2-2 and 2-1 type reflects the molecular heterogeneity of these two proteins. It is known from fractionation experiments with ammonium sulfate as well as with ethanol that the slower Hp bands are enriched in those Hp fractions that are precipitated first. So far, we have not been able to separate any of the Hp bands completely from the others, except the 1-1 band in ascitic fluid of type 2-1. 

Low-molecular-weight extractants can generally be expected to have uneconomic solubilities in most systems, but where high salt concentrations prevail, the solubility may be substantially lower and may be economic. This has been shown to be true for naphthenic and Versatic acids, which have high solubilities in water but appear to be economically useful when used in high ammonium sulfate liquors, such as those produced in the Sherritt-Gordon process for the extraction of cobalt and separation from nickel [12]. 

The solubility of Versatic 911 in water has been studied as a function of both pH and salt concentration for a fixed (0.5 mol dm ) concentration of reagent in the solvent [15] and is illustrated in Fig. 7.10. The use of high salt concentrations (4moldm ammonium sulfate) has been shown to be effective in keeping Versatic 911 losses at pH 7-8 to more economic levels (<100 ppm) in the separation of cobalt from nickel [16]. 

Fig. 7.10 Solubility of Versatic 911 (O.SOmoldm ) in ammonium sulfate solution. (From Ref. 15.)... 

The solubility of Kelex 100 has been reported to be 4.4 (pH 0.5), 1.4 (pH 1.0), and 1.6 (pH 1.5)ppm, in tests employing 0.5moldm Kelex 100 in Solvesso 150 diluent for the extraction of copper from solutions containing about 30 g dm of metals (Cu, Ni, and Co) [21]. Furthermore, over several months no change in the Kelex concentration was found in pilot plant operations with a 0.5moldm Kelex solution [21]. At higher pH values (up to 9) Kelex solubility has been determined at < 1 ppm in ammonium sulfate solutions up to 300 g dm [22]. It would be expected that the amphoteric nature of Kelex would show increasing solubility at pH values above 7, and lower than about 1, similar to the variation in solubility of... 

Enzyme Production and Isolation. The production and isolation of veratryl alcohol oxidase (VAO) was described earlier (25). Laccase produced from the same 12-day culture (8 litres) was isolated from the supernatant by precipitation at 0°C with ammonium sulfate (80% saturation). The precipitate was suspended in 0.05 M Na acetate buffer, pH 5.0 and dialysed overnight against 4 litres of buffer. The soluble material was concentrated by ultrafiltration (Amicon PM10) to about 60 mL and applied to a DEAE-Bio-gel A column (2.5 cm x 35 cm). The column was washed with 20 mL of the same buffer, then eluted with a linear gradient from 0 to 0.6 M NaCl (total volume 550 mL). Fractions were monitored for VAO and laccase activity as described below. 

Native RNase is quite resistant to digestion with trypsin, even at a w/w ratio of 1 20, but small or unfolded fragments would be expected to be digested. When the synthetic enzyme was treated with trypsin, a 70% recovery of protein with a specific activity of 61% was obtained. Treatment of this material with saturated ammonium sulfate (diluted 16 26), pH 4.6, gave 33% of amorphous precipitate and 66% of soluble RNase A. The overall yield from the first Val residue was only 3%, but the specific activity was quite high at 78%. This is as far as the purification was carried out at that time. 

Oxadiazoles of low molecular weight are volatile liquids. The aliphatic derivatives possess a strong ethereal odor, while the aromatic ones remind of aromatic esters. Oxadiazole itself is a liquid boiling at 87°, soluble in water and aU organic solvents. It cannot be recovered from its solutions by distillation because it distils with the vapor of the solvent, even in ethereal solution. It can, however, be isolated as an oil from its aqueous solution by salting out with potassium carbonate, calcium chloride, or ammonium sulfate 55 c). 

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