Ethanol concentrations

To determine the concentration of ethanol in cognac a 5.00-mF sample of cognac is diluted to 0.500 F. Analysis of the diluted cognac gives an ethanol concentration of 0.0844 M. What is the molar concentration of ethanol in the undiluted cognac ... 

Alcohol. The number of driving under the influence of alcohol (DUl) cases reflects the enormity of the dmnken driving problem in the United States (9). Tests to measure blood alcohol concentration are conducted on blood, urine, or breath (10). In the case of urine and breath, the alcohol concentration measured is reported in terms of the equivalent blood alcohol concentration. Most states in the United States presume that a person is under the influence of alcohol with respect to driving a motor vehicle at a blood alcohol concentration of 0.10%, ie, an ethanol concentration >10 g/100 mL of blood. Some states maintain a lower necessary concentration of 0.08%. In some European countries levels are as low as 0.05%. A blood alcohol concentration of 0.10% in a 68-kg (150-lb) person is the equivalent of about four drinks of 80 proof alcohoHc beverage or four 340-g (12-oz) beers in the body at the time of the test (see Beer Beverage spirits, distilled Wine). Ethanol is metabolized at the equivalent rate of about one drink per hour. 

Yeast (qv) metabolize maltose and glucose sugars via the Embden-Meyerhof pathway to pymvate, and via acetaldehyde to ethanol. AH distiUers yeast strains can be expected to produce 6% (v/v) ethanol from a mash containing 11% (w/v) starch. Ethanol concentration up to 18% can be tolerated by some yeasts. Secondary products (congeners) arise during fermentation and are retained in the distiUation of whiskey. These include aldehydes, esters, and higher alcohols (fusel oHs). NaturaHy occurring lactic acid bacteria may simultaneously ferment within the mash and contribute to the whiskey flavor profile. 

Ethanol removed by the vapor stream can be recovered by condensation, vapor recompression, or scmbbiag. Ia the first two methods, the coaceatratioa of the recovered ethanol depends on the relative humidity of the sweep stream and the ratio of sweep and permeation rates. In scmbbiag, the rate of water deflvery to the Hquid-gas coatactor affects the ethanol concentration ia the recovered stream. 

A typical apphcatiou of a simple batch still might be distillation of an ethanol-water mixture at 101.3 kPa (1 atm). The initial charge is 100 mol of ethanol at 18 mole percent, aud the mixture must be reduced to a maximum ethanol concentration in the stiU of 6 mole percent. By using equilibrium data interpolated from Table 13-1,... 

Assume that at t = 0 the feed rate to tray 23 is disturbed by increasing it by 30 percent to 130 moVmin without a change in composition. The resulting ethanol liquid mole frac tion on severaltrays is tracked in Fig. 13-109. Above tray 16, ethanol concentration remains veiy small. Below tray 9, ethanol concentration initially decreases fairly rapidly but... 

System Typical time (h) Typical ethanol concentration (%)... 

The effect of temperature, although significant, is not nearly as great as that from the ethanol content and is greatest at low concentrations of the polar solvent. It is clear, that the solute retention is the least at high ethanol concentrations and high temperatures, which would provide shorter analysis times providing the selectivity of the phase system was not impaired. The combined effect of temperature and solvent composition on selectivity, however, is more complicated and to some extent... 

Reactor productivity was obtained by dividing final ethanol concentration with respect to sugar concentration at a fixed retention time. It was found that the rates of 1.3, 2.3 and 2.8 g 1 1 h 1 for 25, 35 and 50 g 1 1 glucose concentrations were optimal. Ethanol productivities with various substrate concentrations were linearly dependent on retention time (Figure 8.12). The proportionality factor may have increased while the substrate... 

A high glucose concentration of 150 g l 1 was used in continuous fermentation with immobilised S. cerevisiae the obtained data for sugar consumption and ethanol production with retention time are shown in Figure 8.13. As the retention time gradually increased the glucose concentration chopped, while the ethanol concentration profile showed an increase. The maximum ethanol concentration of 47 g l 1 was obtained with a retention time of 7 hours. The yield of ethanol production was approximately 38% compared with batch data, where only an 8% improvement was achieved. 

Time, h Absorbance, 4520nm Cell concentration, g/1 Concentration of carbohydrates, g/1 Ethanol concentration, g/1... 

Ethanol concentration in the fermentation broth is determined by using gas chromatography (HP 5890 series II with HP Chemstation data processing software, Hewlett-Packard, Avondale, PA) with a Poropak Q Column, and a Hewlett-Packard model 3380A integrator. A flame ionisation detector (FID) is used to determine ethanol. The oven temperature is maintained at 180 °C, and the injector and detector temperature are maintained at 240 °C. The sample taken from the fermentation media has to be filtered and any internal standard must be added for analysis based on internal standard methods otherwise, the area under the peak must be compared with known standard samples for calculation based on external standard methods. 

A 5 ml sample is adequate to analyse optical density, glucose/sucrose concentration and ethanol concentration. For sugar analysis you may dilute 1 ml of sample and 9 ml of distilled water to have a suitable concentration range for DNS analysis. 

For each run, calculate and plot the cell biomass concentration, glucose concentration, ethanol concentration, and pH as a function of time. Identify the major phases in batch fermentation lag, exponential, stationary and death. 

Media flow rate, ml/h Retention time, t, h Cell Density, gd Substrate concentration (S), gd 1/5, 1/g - rA, Rate of substrate uptake, g/l.h l/-rA Ethanol concentration, gd... 

Fig. E.5.1. Ethanol concentration profile with respect to fermentation time in batch mode of operation.

Ethanol distributes rapidly, with concentrations in body water 10 times higher than in body fat. The tissues with the greatest blood supply equdibrate most rapidly with arterial blood circulation. Shortly after alcohol ingestion, the ethanol concentration in the brain is higher than the venous concentration. 

The efficiency of the silanization reaction is increased by aU measures enhancing devolatilization of ethanol from the silica compound in the mixer. One possible measure is the reduction of the ethanol concentration in the void space of the mixer, thus increasing the driving force for mass... 

FIG. 3 Plots of half the range of attraction (see Fig. 2) and the apparent thickness of the ethanol adsorption layer vs. the ethanol concentration. 

FIG. 4 FTIR-ATR spectra of ethanol on a silicon oxide surface in ethanol-cyclohexane binary liquids at various ethanol concentrations 0.0, 0.1, 0.3, 0.5, 1.0, and 2.0 mol%. 

At higher ethanol concentrations, ATR spectra should contain the contribution from bnUc species, becanse of the long penetration depth of the evanescent wave, 250 nm. To examine the bulk contribution, the integrated peak intensities of polymer OH peaks of transmission (Ats) and ATR (Aatr) spectra are plotted as a function of the ethanol concentration in Figure 5. The former monitors clnster formation in the bulk liquid, and the latter contains contributions of clusters both on the snrface and in the bulk. A sharp increase is seen in A tr... 

FIG. 5 Plots of integrated peak intensities of polymer OH (3600-3000 cm ) as a function of the ethanol concentration. Filled circles represent the value obtained from the transmission spectra (Ats)> while filled squares represent those from ATR (Aatr)-... 

Fermentation processes typically produce a product with an ethanol concentration of between 7% and 15%. Above this level the yeasts find it difficult to perform. The usual method of concentration is by distillation, which is a very expensive and energy-intensive. This high energy use reduces the overall CO2 neutral benefit often claimed for renewable feedstocks. 

---