Constant volume distillation

This distillation equipment is as described in Sec. 3.3.3.2. For convenience a column containing seven theoretical plates and reboiler is assumed, together with constant volume conditions in the reflux drum. The example is based on that of Luyben (1973, 1990). 

In a 1-1. flask arranged for steam distillation (Note 1), 50 g (0.31 mole) of isonitrosopropioplienone (Org. Syn. 16, 44 Coll. Vol. 2,1943,363) and 500 g. of 10 per cent sulfuric acid are mixed, and the mixture is distilled with steam until about 21. of distillate is collected. During the distillation the flask is heated so that the volume of the reaction mixture is kept roughly constant. The distillation requires about six hours, and at the end of this time the liquid in the flask is dear (Note 2). 

Dissolution was carried out with the paddle method according to USP XXI, using a Prolabo dissolution tester. The dissolution medium was 1000 ml of distilled water at 37 0.5°C and 50 rev min-1. At appropriate time intervals, 5 ml of sample was withdrawn and an equal volume of medium was added to maintain a constant volume. Sample were filtered, diluted with lithium carbonate solution as an internal standard, and analysed using a Dr Lange MD 70 flame photometer. Each dissolution profile is the average of six separate tablets. 

In a 5-1. flask fitted with a long condenser (about 40 cm.) connected to an ice-cooled receiver is placed 2 1. of 7% (by volume) sulfuric acid. The solution is heated to boiling, and the crude monoformate of 1,2-indanediol is added. Steam is introduced and the mixture is steam distilled, while external heat is applied with a flame in order to maintain the boiler contents at a constant volume of 2 1. The steam distillation is carried out at the rate of about 1 1. per hour until 5-6 1. of distillate have been collected and the 2-indanone has stopped distilling (Note 6). The dark-brown oily residue becomes semisolid at room temperature. 

Industrial analysis of hydrocarbon gases 25 years ago was limited almost to Orsat-type absorptions and combustion, resulting in crude approximations and inadequate qualitative information. The more precise method of Shepherd (56) was available but too tedious for frequent use. A great aid to the commercial development of hydrocarbon gas processes of separation and synthesis was the development and commercialization of high efficiency analytical gas distillation units by Podbielniak (50). In these the gaseous sample is liquefied by refrigeration, distilled through an efficient vertical packed column, the distillation fractions collected as gas and determined manometrically at constant volume. The operation was performed initially in manually operated units, more recently in substantially automatic assemblies. 

Figure 21 -27 Atomic absorption calibration curve for Sr added to distilled wafer and standard addition of Sr to aquarium water. All solutions are made up to a constant volume, so the ordinate is the concentration Of added Sr. [Data from L D. Gilles de PeKchy,...

H. Example Calibration of a Trap and Measurement of a Gas Sample. In contrast to the previous example, the objective here is to measure the amount of an entire gas sample, such as the BF3 recovered in the trap-to-trap distillation discussed in Section 5.3.E. in this type of measurement a manometer is included in the calibrated volume, and it is necessary to account for the change of volume as the mercury level changes with changes in pressure. As described in Chapter 7 a constant-volume gas buret can be used, but this is somewhat cumbersome. So the simpler procedure described here is more frequently used. 

Subjects made complete collections of urine and stools throughout each study. Feces for each subject were divided into period lots representing food eaten during each period by use of fecal dyes (brilliant blue and carmine red) and colored glass beads, composited, mixed and sampled for later analyses. Urine for each subject for each day was composited on the basis of time, diluted to a constant volume with distilled water, mixed, sampled and frozen for later analyses. Fasting blood samples were drawn at the beginning of each study and at the end of each experimental period. 

Starting from total reflux conditions, the distillate rate is incremented from zero to D, thereby lowering the reflux rate to Lq - D. Since negligible fluid dynamic lags are assumed, all the liquid rates are instantly lowered to Lj - D. The vapor rates are maintained at Vj. These flow rates and the steady-state total reflux mole fractions are used to calculate the mole fraction derivatives by Equations 17.29 through 17.31. The molar holdups in these equations are calculated from the assumed constant volume holdups multiplied by calculated molar densities. 

The CATHy catalysts are best used below 40 °C, above this temperature we have observed signs of decomposition. In the I PA system, preventing the back-re-action depends on how efficiently acetone is distilled. Normally this would be best done at around 80 °C, the boiling point of isopropanol, but an optimal performance of the catalyst requires ambient temperature or less, and reduced pressure. Whilst acetone can be fractionally distilled, it is simpler to distil the mixture with isopropanol and to maintain constant volume by continuously charging with fresh solvent. In the TEAF system the reaction is normally operated at ambient temperature. Operating at lower temperatures can improve the enantiomeric excess slightly but gives lower rates, for example with 4-fluoroacetophenone the results described in Tab. 3 were achieved. 

Steam distillation is used in British Magnox plants. There, when the HAW stream has been evaporated to the desired solids content, water is substituted for radioactive feed for about 2 days and evaporation continued at constant volume. In this way the acidity of the concentrate is reduced to about 4 M. 

The dione adduct 25 (440 mg) and aluminum isopropoxide (1.83 g) were dissolved in dry isopropanol (8 mL). The mixture was boiled gently, and acetone and isopropanol were distilled slowly from the reaction mixture through a short column. From time to time isopropanol was added to maintain a constant volume. After one hour no more acetone could be detected in the distillate. The reaction mixture was then concentrated under reduced pressure, treated with ice-cold 2 N hydrochloric acid, and extracted with methylene chloride/ether (1 3). The organic phase was washed with sodium bicarbonate and saturated sodium chloride solution, and concentrated. The residue was crystallized twice from acetone/ether, to give 230 mg of colorless lactone 26. 

Buffle et al (1978) found UF to be better than GPC as the adsorption capacity is lower. Cascade filtration is recommended to avoid MWCO changes due to adsorption effects, and concentrations less than a few hundred mgL are essential. The washing method, where the concentrate volume is kept constant with distilled water, produced better results than the concentration method. Electrolyte concentration, pH, and pressure difference were reported to play a minor role. The major source of error is the membrane itself and a new membrane should be used for each filtration. Belin et al (1993) fractionated samples using UF and XAD and found very similar fluorescence characteristics of the fractions obtained. 

In Vivo Absorption Studies IVIale Wister albino rats, 270 - 310 g, were fasted for 2k h prior to drug administration. Ketoprofen powder or its physical mixture with methyl-3-CD (molar ratio l l) was freshly suspended in distilled water and administrated- into the stomach of a rat through a sonde at a dose of 25 mg/kg (ketoprofen) in a constant volume of 5 ml/kg. Blood samples were obtained from the femoral artery via a cannula and immediately centrifuged at 3000 rpm to obtain plasma samples. The concentration of ketoprofen in plasma was determined... 

The amount of carbon in a sample can be directly determined experimentally by calorimetry. A bomb calorimeter is a constant-volume device made from stainless steel that measures the change in temperature of a known volume of distilled water as a combustible material... 

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