Solubility dilute solutions

Reagent A is particularly useful for the treatment of the lower aliphatic aldehydes and ketones which are soluble in water cf. acetaldehyde, p. 342 acetone, p. 346). The Recent is a very dilute solution of the dinitrophenylhydrazine, and therefore is used more to detect the presence of a carbonyl group in a compound than to isolate sufficient of the hydrazone for effective recrystallisation and melting-point determination. 

Alkyl mercaptans are partly soluble in solutions of caustic alkalis, but their salts are hydrolysed in dilute aqueous solution back to the free mercaptans. Thiophenols are soluble in alkah hydroxide solutions. Upon treatment with sodium, hydrogen is evolved. 

RCH(OH)=CHCOR or -keto esters RCH(OH)=CHCOOR ) dissolve in dilute sodium hydroxide solution, i.e., contain an acidic group of sufficient strength to react with the alkah. Carboxyhc acids and sulphonic acids are soluble in dilute solutions of sodium bicarbonate some negatively-substituted phenols, for example, picric acid, 2 4 6-tribromo-phenol and 2 4-dinitrophenol, are strongly acidic and also dissolve in dilute sodium bicarbonate solution. 

Electrolytic Solvent. The use of DMAC as a nonaqueous electrolytic solvent is promising because salts are modesdy soluble ia DMAC and appear to be completely dissociated ia dilute solutions (18). 

Polymers in Solution. Polyacrylamide is soluble in water at all concentrations, temperatures, and pH values. An extrapolated theta temperature in water is approximately —40° C (17). Insoluble gel fractions are sometimes obtained owing to cross-link formation between chains or to the formation of imide groups along the polymer chains (18). In very dilute solution, polyacrylamide exists as unassociated coils which can have an eUipsoidal or beanlike stmcture (19). Large aggregates of polymer chains have been observed in hydrolyzed polyacrylamides (20) and in copolymers containing a small amount of hydrophobic groups (21). 

Sodium monofluorophosphate, mp 625°C, is soluble ia water to the extent of 42 g/100 g solution. The pH of a 2% solution is between 6.5 and 8.0. Dilute solutions are stable indefinitely ia the absence of acid or cations that form iasoluble fluorides. 

Hafnium is readily soluble in hydrofluoric acid and is slowly attacked by concentrated sulfuric acid. Hafnium is unaffected by nitric acid in all concentrations. It is resistant to dilute solutions of hydrochloric acid and sulfuric acid. Hafnium is attacked by all mineral acids if traces of fluorides are present. Hafnium is very resistant to attack by alkaUes. 

A.cetohexamide. Acetohexamide or l-[(p-acetylphenyl)sulfon5l]-3-cyclohex-ylurea, mol wt 324.42, is a white, practically odorless crystalline powder that has the trade name Dymelor. It is practically insoluble in water and in ether, soluble in pyridine and in dilute solutions of alkaU hydroxides, and slightly soluble in alcohol and in chloroform. 

Lead Carbonate. Lead carbonate [598-63-0] PbCO, mol wt 267.22, d = 6.6g/cm, forms colorless orthorhombic crystals it decomposes at about 315°C. It is nearly insoluble in cold water (0.00011 g/100 mL at 20°C), but is transformed in hot water to the basic carbonate, 2PbC03 Pb(OH)2. Lead carbonate is soluble in acids and alkalies, but insoluble in alcohol and ammonia. It is prepared by passing CO2 iuto a cold dilute solution of lead acetate, or by shaking a suspension of a lead salt less soluble than the carbonate with ammonium carbonate at a low temperature to avoid formation of basic lead carbonate. 

Evolution of ammonia from a boiling dilute solution of diammonium phosphate gradually reduces the pH. This process is used commercially to control the precipitation of alkaH-soluble—acid-insoluble coUoidal dyes on wool. Other ammonium orthophosphate salts of interest are ammonium hemiphosphate [28537-48-6] NH4H2PO4 H3PO4, and its hydrate [28037-74-3], as well as the trihydrate [78436-07-4] of DAP. 

The extraction of metal ions depends on the chelating ability of 8-hydroxyquinoline. Modification of the stmcture can improve its properties, eg, higher solubility in organic solvents (91). The extraction of nickel, cobalt, copper, and zinc from acid sulfates has been accompHshed using 8-hydroxyquinohne in an immiscible solvent (92). In the presence of oximes, halo-substituted 8-hydroxyquinolines have been used to recover copper and zinc from aqueous solutions (93). Dilute solutions of heavy metals such as mercury, ca dmium, copper, lead, and zinc can be purified using quinoline-8-carboxyhc acid adsorbed on various substrates (94). 

Silver Chloride. Silver chloride, AgCl, is a white precipitate that forms when chloride ion is added to a silver nitrate solution. The order of solubility of the three silver halides is Cl" > Br" > I. Because of the formation of complexes, silver chloride is soluble in solutions containing excess chloride and in solutions of cyanide, thiosulfate, and ammonia. Silver chloride is insoluble in nitric and dilute sulfuric acid. Treatment with concentrated sulfuric acid gives silver sulfate. 

Choline is a strong base (pif = 5.06for0.0065-0.0403 Afsolutions ) (3). It crystallizes with difficulty and is usually known as a colorless deHquescent sympy hquid, which absorbs carbon dioxide from the atmosphere. Choline is very soluble in water and in absolute alcohol but insoluble in ether (4). It is stable in dilute solutions but in concentrated solutions tends to decompose at 100°C, giving ethylene glycol, poly(ethylene glycol), and trimetbylamine (5). 

Figure 4.3 The variation of the solubility of a dilute solutes in an A-B alloy...

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