Salting-out of carbon dioxide

To apply the correlation of Figure 10 for prediction of the salting out of carbon dioxide by ammonium hydrosulfide and bicarbonate solutions we need to correct for the differences of their partial molar volumes from that of sodium chloride. Partial molar volumes were obtained from Ellis and McFadden(53). Volume change of the hydrosulfide and bicarbonate are equal within 0.2 cm3/mol at temperatures up to 100 C and differ very little at still higher temperatures thus, we assume that the changes with temperature of the salting-out coefficients of the two salts are equal up to... 

Table VIII. EFFECT OF TEMPERATURE ON SALTING-OUT OF CARBON DIOXIDE BY SODIUM CHLORIDE AND CALCIUM CHLORIDE SOLUTIONS... 

Weak acids with weak bases. The titration of a weak acid and a weak base can be readily carried out, and frequently it is preferable to employ this procedure rather than use a strong base. Curve (c) in Fig. 13.2 is the titration curve of 0.003 M acetic acid with 0.0973 M aqueous ammonia solution. The neutralisation curve up to the equivalence point is similar to that obtained with sodium hydroxide solution, since both sodium and ammonium acetates are strong electrolytes after the equivalence point an excess of aqueous ammonia solution has little effect upon the conductance, as its dissociation is depressed by the ammonium salt present in the solution. The advantages over the use of strong alkali are that the end point is easier to detect, and in dilute solution the influence of carbon dioxide may be neglected. 

The synthesis of DMC from EC and methanol was carried out in a batch reactor using various quaternary ammonium salt catalysts under carbon dioxide pressure. 

The microalgae are cultured in bioreactors under solar or artiflcial light in the presence of carbon dioxide and salts. The bioreactors may be closed systems made of polyethylene sleeves rather than open pools. Optimal conditions for pigment production are low to medium light intensity and medium temperatures (20 to 30°C). Pigment extraction is achieved by cell breakage, extraction into water or buffered solution, and centrifugation to separate out the filtrate. The filtrate may then be partly purified and sterilized by microfiltration and spray dried or lyophilized. 

A second type of ternary electrolyte systems is solvent -supercritical molecular solute - salt systems. The concentration of supercritical molecular solutes in these systems is generally very low. Therefore, the salting out effects are essentially effects of the presence of salts on the unsymmetric activity coefficient of molecular solutes at infinite dilution. The interaction parameters for NaCl-C02 binary pair and KCI-CO2 binary pair are shown in Table 8. Water-electrolyte binary parameters were obtained from Table 1. Water-carbon dioxide binary parameters were correlated assuming dissociation of carbon dioxide in water is negligible. It is interesting to note that the Setschenow equation fits only approximately these two systems (Yasunishi and Yoshida, (24)). 

Table IX. CORRELATION EQUATIONS FOR SALTING-OUT OF AMMONIA, CARBON DIOXIDE, AND HYDROGEN SULFIDE...

Data on the effect of temperature on salting out of ammonia are even less satisfactory than those for carbon dioxide. Perman obtained some data on a potassium sulfate solution at temperatures of 40° to 59°C and on two ammonium chloride solutions at temperatures from 19° to 58°C.(54). His ammonia concentrations were in the range of 5 to 13 molal. His data indicate only small changes in the salting-out coefficient, but the coefficient for ammonium chloride increases with temperature, which is contrary to the effect found with carbon dioxide. 

The partial molar volume of hydrogen sulfide is nearly equal to that of carbon dioxide (Table 1), and we tentatively assume that changes in its salting-out coefficients with temperature are the same as those of carbon dioxide. 

J. J. Watts and W. A. Richards patented the preparation of this salt by removing the proper quantity of carbon dioxide from sodium hydrocarbonate by adding sodium hydroxide, sodium carbonate, or the hydroxides of the alkaline earths, and crystallizing the soln. at about 35° C. Winkler obtained it from carbonated liquor of the ammonia-soda process and T. M. Chatard by the spontaneous evaporation of soln. of normal sodium carbonate which had been exposed to the air some time and thereby absorbed carbon dioxide. There is a fairly general agreement that a temp, below 35° is not favourable to the formation of trona and that the crystals develop better in sodium chloride soln. and excess of the normal carbonate also favours the formation of trona. J. J. Watts and W. A. Richards say that if an excess of the hydrocarbonate be used, it crystallizes out unchanged. T. M. Chatard studied the influence of the composition of the soln. on the formation of trona, and obtained the results indicated in Table LIV with soln. containing a mol. of the normal carbonate. H. N. McCoy and C. D. Test have studied the conditions under which the sesquiearbonate is formed, and their results are summarized in Fig. 73. 

Salt effects of lithium chloride and calcium chloride on the solubility of carbon dioxide in a mixture of methanol and water were observed at 25°C and 1 atm. Experimental results can be correlated by the Setschenow equation for a fixed solvent composition of salt-free basis. The salting-out parameter is not linear with solvent composition, which is opposite to the results obtained when a mixed salt is used. 

Potassium niobate, 8K20.7Nb20B.82H2Q, predpitates out on slow evaporation of solutions of either the 4 3 salt or the 7 6 salt. It forms rhombic bipyramids which can be recrystallised unchanged a b c=0 9584 1 0 7083. Twenty-three molecules of water are lost at 100° C. It readily yields supersaturated solutions. When its aqueous solutions are treated with a current of carbon dioxide they predpitate salts which contain a larger proportion of niobic add.9... 

Potassium Metatantalate, K20.Ta205, is produced when the 4 3 salt is heated and the product washed with water. It is insoluble in water. The 2 8 salt, 2K20.3Ta205.6H20, is precipitated out by the action of carbon dioxide on the aqueous extract of a fused mixture of tantalum pentoxide and potassium carbonate.5 Continued boiling of this salt with water yields the 1 2 salt, K20.2Ta20,.8H20. The anhydrous 3 7 salt has also been reported. 

The reaction mixture is then cooled by an ice-salt mixture. The separatory funnel is replaced by a two-hole rubber stopper containing a thermometer (bulb immersed in the reaction mixture) and a glass tube drawn out to make a fine capillary (Note 5). When the temperature of the reaction mixture has reached — 7°, the condenser is replaced by an entry tube, 10 mm. in diameter and adjusted so the end is about 50 mm. above the surface of the reaction mixture (Note 6). The reaction mixture is stirred, and dry carbon dioxide is added through this tube (Note 7). The rate of flow of the carbon dioxide is regulated so that the temperature of the reaction mixture does not rise above —2°. The time required for the completion of the reaction varies from one and one-fourth to one and one-half hours. When the reaction is complete, the temperature falls below —7° and does not rise on increasing the rate of flow of carbon dioxide. 

Of other examples which yield leuco compounds, Indigo may be estimated by titrating the sulphonated dye in presence of Rochelle salt Magenta in Rochelle salt solution Eosin and Rhodamine in presence of Rochelle salt and alcohol, the latter to keep the leuco compound in solution. All these titrations are carried out on the boiling dye solution and in presence of carbon dioxide. 

This method can be used with any metal carbonate and any acid, providing the salt produced is soluble. The typical experimental procedure is similar to that carried out for an acid and a metal. For example, copper(n) carbonate would be added in excess to dilute nitric acid. Effervescence would be observed due to the production of carbon dioxide. 

The formula of carbon dioxide is C02, that of carbon disulphide CS2 and it is evident that an intermediate substance should exist of the formula COS. This substance is carbon oxysulphide. It is a gas, prepared by heating thiocyanic acid, HSCN, the ammonium salt of il which is produced when ammonia is passed through a mixture of carbon disulphide and alcohol CS2 + 2NHg.Alc = H2S + (NH4) SCN.Alc. On evaporation of the alcohol the ammonium thiocyanate crystallises out. This salt, distilled with sulphuric acid, yields in passing the acid HSCN, which, on account of the high temperature, reacts with water, forming ammonia (which yields ammonium sulphate with the sulphuric acid) and carbon oxysulphide, COS HSCN + H20 = NHS + COS. 

Barium Iridicyanide, Ba3(IrC6N6)a.18H20, was obtained by Martius 1 as the result of treating the copper salt with excess of barium hydroxide solution. The excess of barium is removed by passage of carbon dioxide through the liquid, and upon slow evaporation the salt separates out in large trimetric crystals. Exposed to dry air the crystals effloresce, still, however, containing six molecules of water, which are completely expelled at 100° C. 

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