Solution, concentrated

For solutions (or rather mixtures) of s at higher concentrations beyond the realms of Henry s law, we depart from the traditional notion of solvation and must use the definition as presented in section 7.2. There exists a variety of data which measures the extent of deviation from dilute ideal solutions. These include tables of activity coefficients, osmotic coefficients, and excess functions. All of these may be used to compute solvation thermodynamic quantities. 

As always, our starting point is the general expression for the chemical potential of s in the liquid phase l, equation (7.16), 

The chemical potential in the same system may be expressed in conventional thermodynamics as 

This quantity is equivalent to the difference between the solvation Gibbs energy of s in the phase l, and the solvation Gibbs energy of s in the same phase except for taking the limit ps — 0. Using the notation of section 7.2, we may rewrite this quantity as 

from the activity coefficient (based on the p-concentration scale), one can compute the solvation Gibbs energy of s in a liquid phase l (containing any quantity of s), relative to the solvation Gibbs energy of s in the same phase but 

All of the examples described above have involved dilute solutions, where transmission IR spectroscopy is relatively easy to use, and there were sufficient windows in the spectrum of the supercritical solvent to permit the detection of the molecules of interest. However, this is not always the case. For example the IR spectrum of SCCO2 is totally absorbing between ca. 3700-3500 and 

2600-2100cm. Hence, for the water in SCCO2 microemulsions study, the bulk of the work was performed with D2O, because the important vibrational lines of H2O were obscured by fundamental modes of SCCO2 [60]. However, such isotopic substitution is not always feasible. 

The behaviour of polymers as one moves from a dilute to a more concentrated regime has excited considerable interest in recent years. Nystrom and co-workers have been particularly active in this area, concentrating mainly on transport 

Fedors has proposed a relationship between ( /l and c, which is valid over a wide concentration range and can be used to measure 1 from the determination of the relative viscosity at a single polymer concentration. Nishio and Wada have observed the transition from intramolecular motion within a polystyrene molecule to a co-operative diffusion process on passing from dilute to concentrated solutions, where D also increased despite a corresponding increase in viscosity. The radius of gyration of polymers in semi-concentrated solutions has been investigated by Aharoni and Walsh.  

Chemical equilibrium in homogeneous systems—Concentrated solutions 

Experimental Results Obtained in the Measurement of High Osmotic Pressures 

These results give some idea ofthe enormous values actually reached in concentrated solutions The curve (Fig 27) shows the osmotic pressure plotted against concentration, so as to show the departure of the P values from the simple linear relation, which holds m dilute solutions The straight line is drawn on the usual assumption that 1 gram molecular weight of solute per liter (solution) should give an osmotic pressure of 22 4 atmospheres 

Other sugars were also employed, and in later papers an account is given of similar very accurate measurements both of osmotic pressure and lowering of vapour pressure, due to calcium ferrocyanide m water, this salt being a very soluble one, and one which at the same time is practically stopped by the copper-ferrocyanide semi-permeable membrane (Earl of Berkeley, E G J Hartley, and C V Burton, PM Trans, 209 A, 177, 1909 Dilute solutions ofthe same solute were also investigated by the Earl of Berkeley, E G J Haitley, and J Stephenson, ibid, p 319 ) For details the reader is again referred to the ongmal papers The object of the work referred to was to test Porter s equation This equation will be taken later 

Theoretical Treatment of the Osmotic Pressure of Concentrated Solutions 

With increasing polymer concentration, the number and structural complexity of crystals and their aggregates increase hence, optical microscopy is often more useful than TEM. Of general interest is the progression toward spherulitic morphology most research with solutions of intermediate and high concentrations has been carried out with polyethylene. 

Wunderlich and Sullivan [53] investigated polyethylene dendrites formed below 80°C by cooling toluene solutions at a rate of ca. 5°C/min. The most dilute solutions gave dendrites with primary growth arms along a 

The transition from solution crystallization to melt crystallization was followed by Keith in a revealing 

Further increase of the concentration results in aphase separation in the melt small drops of undissolved TiCLr are clearly visible on the surface and in the bulk of the electrolyte. 

Accordingly, the reduction pattern becomes much more complicated at potentials more negative -1 V mol L . Series of poorly resolved waves appear in potential region about 1 to 2 V in the CVs (Fig. 6.12) and up to five peaks are observed in the derivative curve of the CP data (Fig. 6.20). 

The CP transition times and CV peaks for concentrated solutions can be hardly interpreted in terms of simple stepwise reduction mechanism. The reason of such behaviotu can be related to the phase separation, which is observed in concentrated solutions. In fact, the electrochemical process takes place in heterogeneous system containing two liquid phases—IL saturated with TiCl4 and vice versa. There are no theoretical studies of this case in the literature yet. 

As follows from the results, the overall electrochemical reduction in the system TiCl4-BMMlmBF4 can be represented in terms of general scheme of stepwise reaction mechanism (1.9), which, though simplified, remains very good approximation for the processes in IL media. 

In diluted solutions, the Ti(ll) intermediate is more stable, and also the disproportionation kinetics of Ti(l) can be detected. Total four-electron reduction to Ti(0) is observed with the formation of Ti(lll) and Ti(I) as the relatively stable intermediates. 

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Timmermans, J. "The Physico-Chemical Constants of Binary Systems in Concentrated Solutions," Vol. 1-4, Interscience, New York, 1959-60. 

A logical division is made for the adsorption of nonelectrolytes according to whether they are in dilute or concentrated solution. In dilute solutions, the treatment is very similar to that for gas adsorption, whereas in concentrated binary mixtures the role of the solvent becomes more explicit. An important class of adsorbed materials, self-assembling monolayers, are briefly reviewed along with an overview of the essential features of polymer adsorption. The adsorption of electrolytes is treated briefly, mainly in terms of the exchange of components in an electrical double layer. 

Equation XI-27 shows that F can be viewed as related to the difference between the individual adsorption isotherms of components 1 and 2. Figure XI-9 [140] shows the composite isotherms resulting from various combinations of individual ones. Note in particular Fig. XI-9a, which shows that even in the absence of adsorption of component 1, that of component 2 must go through a maximum (due to the N[ factor in Eq. XI-27), and that in all other cases the apparent adsorption of component 2 will be negative in concentrated solution. 

First-order difference neutron scadermg methods for die analysis of concentrated solutions of anions and... 

Graessley W W 1993 Viscoelasticity and flow in polymer melts and concentrated solutions Physical Properties of Polymers ed J E Mark et al (Washington, DC ACS) pp 97- 143... 

The head element nitrogen does not react. White phosphorus, however, reacts when warmed with a concentrated solution of a strong alkali to form phosphine, a reaction which can be regarded as a disproportionation reaction of phosphorus ... 

The formation of halatefV) and halide ions by reaction (11.4) is favoured by the use of hot concentrated solutions of alkali and an excess of the halogen. 

The bond dissociation energy of the hydrogen-fluorine bond in HF is so great that the above equilibrium lies to the left and hydrogen fluoride is a weak acid in dilute aqueous solution. In more concentrated solution, however, a second equilibrium reaction becomes important with the fluoride ion forming the complex ion HFJ. The relevant equilibria are ... 

Hot concentrated solutions of chloric(VII) acid and chlorates(VlI), however, react vigorously and occasionally violently with reducing agents. 

If it is passed into a concentrated solution of a chloride, however, a chlorochromate( l) is formed ... 

Concentrate each of the two solutions (or eluates) to about 20 ml, by distilling off the greater part of the benzene, the distilling-flask being immersed in the boiling water-bath. Then pour the concentrated solution into an evaporating-basin, and evaporate the remaining benzene (preferably in a fume-cupboard) in the absence of free flames, i.e., on an electrically heated water-bath, or on a steam-bath directly connected to a steam-pipe. Wash the dry residue from the first eluate with petrol and then dry it in a desiccator pure o-nitroaniline, m.p. 72°, is obtained. Wash the second residue similarly with a small quantity of benzene and dry pure />--nitroaniline, m.p. 148" , is obtained. Record the yield and m.p. of each component. 

Add 15 g, of chloroacetic acid to 300 ml. of aqueous ammonia solution d, o-88o) contained in a 750 ml. conical flask. (The manipulation of the concentrated ammonia should preferably be carried out in a fume-cupboard, and great care taken to avoid ammonia fumes.) Cork the flask loosely and set aside overnight at room temperature. Now concentrate the solution to about 30 ml. by distillation under reduced pressure. For this purpose, place the solution in a suitable distilling-flask with some fragments of unglazed porcelain, fit a capillary tube to the neck of the flask, and connect the flask through a water-condenser and receiver to a water-pump then heat the flask carefully on a water-bath. Make the concentrated solution up to 40 ml. by the addition of water, filter, and then add 250 ml. of methanol. Cool the solution in ice-water, stir well, and set aside for ca. I hour, when the precipitation of the glycine will be complete. 

When an aqueous solution of benzenediazonium chloride is added to a cold concentrated solution of potassium hydroxide, the unstable potassium diazo-tate, C(HjN NOK, is formed, and this when heated with alkali to 130° changes to the isomeric but far more stable potassium isodiazotate it is probable that these copipounds have the structures (A) and (B) respectively. 

Chill the concentrated solution of the amine hydrochloride in ice-water, and then cautiously with stirring add an excess of 20% aqueous sodium hydroxide solution to liberate the amine. Pour the mixture into a separating-funnel, and rinse out the flask or basin with ether into the funnel. Extract the mixture twice with ether (2 X25 ml.). Dry the united ether extracts over flake or powdered sodium hydroxide, preferably overnight. Distil the dry filtered extract from an apparatus similar to that used for the oxime when the ether has been removed, distil the amine slowly under water-pump pressure, using a capillary tube having a soda-lime guard - tube to ensure that only dry air free from carbon dioxide passes through the liquid. Collect the amine, b.p. 59-61°/12 mm. at atmospheric pressure it has b.p. 163-164°. Yield, 18 g. 

A concentrated solution of monochloroacetic acid is neutralised with sodium bicarbonate, and then heated with potassium cyanide, whereby sodium cyano-acetate is obtained ... 

Make a concentrated solution of anthracene in hot acetone. To about 2 ml. of this solution add a cold concentrated acetone solution of picric acid drop by drop, and note the formation of a red coloration which becomes deeper on further addition of the acid. If excess of picric acid is added, however, the solution becomes paler in colour, and this is to be avoided if possible. Boil to ensure that both components are in solution and then transfer to a small porcelain basin or watch-glass ruby-red crystals of anthracene picrate separate out on cooling. The product, however, is often contaminated with an excess of either anthracene or of picric acid, which appear as yellowish crystals. 

Then again remove T, and drop a weighed pellet of the solute through the side arm A. Stir the mixture until a clear solution is obtained, and then repeat the above process until three consistent readings of the freezing point of the solution have been obtained. Then add a second weighed pellet of the solute, and determine the freezing-p>oint of this more concentrated solution in the same way. 

As supplied by chemical dealers a concentrated solution of FeCb acidified... 

Iodine Solution. Cold saturated aqueous solution. (If a more concentrated solution is required, add i g. of powdered iodine to a solution of 2 g. of potassium iodide in a minimum of water, and dilute the solution to 100 ml.)... 

Sodium and potassium hydroxides. The use of these efficient reagents is generally confined to the drying of amines (soda lime, barium oxide and quicklime may also be employed) potassium hydroxide is somewhat superior to the sodium compound. Much of the water may be first removed by shaking with a concentrated solution of the alkali hydroxide. They react with many organic compounds (e.g., acids, phenols, esters and amides) in the presence of water, and are also soluble in certain organic liquids so that their use as desiccants is very limited... 

The use of a ternary mixture in the drying of a liquid (ethyl alcohol) has been described in Section 1,5 the following is an example of its application to the drying of a solid. Laevulose (fructose) is dissolved in warm absolute ethyl alcohol, benzene is added, and the mixture is fractionated. A ternary mixture, alcohol-benzene-water, b.p. 64°, distils first, and then the binary mixture, benzene-alcohol, b.p. 68-3°. The residual, dry alcoholic solution is partially distilled and the concentrated solution is allowed to crystallise the anhydrous sugar separates. 

Absolute diethyl ether. The chief impurities in commercial ether (sp. gr. 0- 720) are water, ethyl alcohol, and, in samples which have been exposed to the air and light for some time, ethyl peroxide. The presence of peroxides may be detected either by the liberation of iodine (brown colouration or blue colouration with starch solution) when a small sample is shaken with an equal volume of 2 per cent, potassium iodide solution and a few drops of dilute hydrochloric acid, or by carrying out the perchromio acid test of inorganic analysis with potassium dichromate solution acidified with dilute sulphuric acid. The peroxides may be removed by shaking with a concentrated solution of a ferrous salt, say, 6-10 g. of ferrous salt (s 10-20 ml. of the prepared concentrated solution) to 1 litre of ether. The concentrated solution of ferrous salt is prepared either from 60 g. of crystallised ferrous sulphate, 6 ml. of concentrated sulphuric acid and 110 ml. of water or from 100 g. of crystallised ferrous chloride, 42 ml. of concentrated hydiochloric acid and 85 ml. of water. Peroxides may also be removed by shaking with an aqueous solution of sodium sulphite (for the removal with stannous chloride, see Section VI,12). 

Silver nitrite. Warm concentrated solutions of silver nitrate (containing 48 g. of AgNOj) and potassium nitrite (containing 30 g. of KNOj) are mixed, and the mixture is allowed to cool. The silver nitrite which separates is filtered off and washed with water. It may be recrystallised from water at 70°, and is dried either in a vacuum desiccator or in an air oven at about 40° the yield is about 90 per cent. Silver nitrite should be stored in an tightly-stoppered amber bottle. 

Saccharic acid. Use the filtrate A) from the above oxidation of lactose or, alternatively, employ the product obtained by evaporating 10 g. of glucose with 100 ml. of nitric acid, sp. gr. 1 15, until a syrupy residue remains and then dissolving in 30 ml. of water. Exactly neutralise at the boiling point with a concentrated solution of potassium carbonate, acidify with acetic acid, and concentrate again to a thick syrup. Upon the addition of 50 per cent, acetic acid, acid potassium saccharate sepa rates out. Filter at the pump and recrystaUise from a small quantity of hot water to remove the attendant oxahc acid. It is necessary to isolate the saccharic acid as the acid potassium salt since the acid is very soluble in water. The purity may be confirmed by conversion into the silver salt (Section 111,103) and determination of the silver content by ignition. 

If acetaldehyde is warmed with a concentrated solution of an alkali hydroxide, it is converted into a resinous product resulting from repeated aldol condensations between aldol, crotonaldehyde and acetaldehyde. 

Undecylenic acid (or 10-undecenoic acid) (I), a comparatively inexpensive commercial product obtained from castor oil, reacts with bromine in dry carbon tetrachloride to give 10 11-dibromoundecoic acid (II), which upon heating with a concentrated solution of potassium hydroxide yields 10-niidecynoic acid (III) ... 

By adding a concentrated solution of sodium borofluoride to a solution of a diazonium salt, the diazonium fluoborate is precipitated this decomposes into the aryl fluoride when cautiously heated, for example ... 

Place 45 g. (43 ml.) of benzal chloride (Section IV,22), 250 ml. of water and 75 g. of precipitated calcium carbonate (1) in a 500 ml. round-bottomed flask fltted with a reflux condenser, and heat the mixture for 4 hours in an oil bath maintained at 130°. It is advantageous to pass a current of carbon dioxide through the apparatus. Filter off the calcium salts, and distil the filtrate in steam (Fig. II, 40, 1) until no more oil passes over (2). Separate the benzaldehyde from the steam distillate by two extractions with small volumes of ether, distil off most of the ether on a water bath, and transfer the residual benzaldehyde to a wide-mouthed bottle or flask. Add excess of a concentrated solution of sodium bisulphite in portions with stirring or shaking stopper the vessel and shake vigorously until the odour of benzaldehyde can no longer be detected. Filter the paste of the benzaldehyde bisulphite compound at the pump... 

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