Monday, December 30, 2019

The Vector Autoregressive Model Finance Essay - Free Essay Example

Sample details Pages: 7 Words: 2164 Downloads: 7 Date added: 2017/06/26 Category Finance Essay Type Narrative essay Did you like this example? Researches on the causal relationship between equity prices and exchange rates have been conducted with various econometric methods. In this study, I employ the vector autoregressive model and dynamic Granger (1969) causality test to examine the relationship between the variables under study. Empirical studies which are premised on time series data assume that the underlying time series is stationary. Don’t waste time! Our writers will create an original "The Vector Autoregressive Model Finance Essay" essay for you Create order On the contrary, many empirical studies have shown that this assumption is not always true and that a significant number of time series variables are non-stationary (Engle and Granger, 1987). Thus, employing a non-stationary time series data in a regression analysis may result in spurious results (Granger and Newbold (1974)). Therefore, embarking on studies involving time series data necessitates that stationary test is conducted to establish the underlying process of the data series. 3.1 Stationarity Test A data generating process is considered stationary if it has time-invariant first and second moments, and the covariance of two time periods is constant notwithstanding which time periods are used and the distance between them, Gujarati (1995). The process is said to be weakly stationary if the two first conditions are fulfilled but the covariance between two time periods depends on the distance between the time periods, but not on when it is calculated. If the process is stationary around a trend, it is said to be trend-stationary. There are a variety of unit root tests used in the econometric literature principally Augmented Dickey-Fuller (ADF), Dickey-Fuller, Phillip-Perron, Ng-Perron tests, etc to investigate whether the time series data used in a study are stationary or not. I employ the Augmented Dickey-Fuller to examine the stationarity of the variables. 3.1.1 Augmented Dickey-Fuller (ADF) Test The ADF model tests the null hypothesis that there is unit root, against the alternative hypothesis that there is no unit root in the regression. The regression for the ADF test is estimated as follows: (1) where represents the variable that we are examining its properties, is the difference operator, , and are the coefficients to be estimated, p is the chosen lag length, t is the time trend, and t is the white-noise error term. has a stochastic trend under the null hypothesis but under the alternative hypothesis is stationary. Generally, the lag length for conducting the ADF test is unknown but can be estimated using information criteria such as the Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC) applied to the regressions of the form in equation (1). If the Data Generating Process (DGP) is stationary in the data series at levels, then it will be concluded to be integrated of order zero, I (0). On the contrary, it is not always the case and the un derlying process of the data series may be non-stationary. In effect, the original series need to be transformed into a stationary state by taking difference (d) times. If after taking first difference of the series, it is found that they are all stationary then we can conclude that the DGP is integrated at order one, I (1). Moreover, if the original series used in the study are found out to be integrated of the same order, it is useful to test for cointegration relationship between the integrated variables. 3.2 Cointegration Test It is generally accepted that regression which involves non-stationary time series will lead to spurious results. However, Engle-Granger (1987) proposed that a linear combination of these non-stationary series may be stationary in which case we can say that the series are cointegrated. To compute the Engle-Granger test, let the vector denote the tth observation on N time series, each of which is known to be I (1). If these times series are cointegrated, there exists a vector such that the stochastic process with observation is I (0). However, if they are not cointegrated, there will be no vector with this property, and any linear combination of y1 through yN and a constant will still be I(1). The cointegration regression is estimated as follows: (2) With respect to this regression, it is assumed that all the variables are I (1) and might cointegrate to form a stationary relationship, and thus will result in a stationary residual term. The null hypothesis of non-cointegrati on is that the residual term is non-stationary. Unit root test is conducted on the residuals to find out whether they are stationary or otherwise. To this end, the ADF test is employed to conduct the unit root test. If the residuals are stationary, then one rejects the null hypothesis of non-cointegration. However, if they are non-stationary, then one accepts the null hypothesis of non-cointegration. 3.3 Vector Autoregressive (VAR) Model A vector autoregression is a set of k series of regressions in which the regressors are lagged values of all the k series. The underlying assumption of the model is that all variables are endogenous a priori, and allowance is made for rich dynamics. VAR models offer some level of flexibility and therefore easy to use for analysing multiple time series. This is against the backdrop that one needs not to specify which variables are exogenous or endogenous. However, there are still some difficulties associated with VAR models. In the first place, it is not easy to identify which variables have significant effect on the dependent variable. Also, there is a strict condition that all the data series in the VAR should be stationary. However, most financial time series are non-stationarity. In case the variables are found not to be stationary at levels, then according to Granger (1969), it is more appropriate to estimate VAR or Vector Error Correction Model depending on whether the series are cointegrated or not. The vector error correction model is discussed in the subsequent section. The simplest form of the VAR is the bivariate model. The bivariate model can generally be estimated as follows: (3) where ÃÆ'Æ’Â °Ãƒâ€šÃ‚ Ãƒâ€šÃ‚ ¢it is a white noise term with E (ÃÆ'Æ’Â °Ãƒâ€šÃ‚ Ãƒâ€šÃ‚ ¢it) = 0, E (u1tu2t) =0. 3.4 The Granger Causality Test According to Granger (1969) a variable X could be defined as causal to a time series variable Yif the former helps to improve the forecast of the latter. Thus, X does not Granger-cause Y if Pr (|) = Pr (|) (4) where Pr (.) is the conditional probability, is the information set at time t on past values of Y and is the information set containing values of both Xand Yup to time point t. If the variables are found not to be cointegrated, then the following VAR will be estimated and the Granger causality test is consequently conducted: (5) (6) where SI is the stock price, ER is the exchange rate of the Ghana cedi to the US dollar andare uncorrelated white noise terms, ln represents the natural log, ÃŽ difference operator and t denotes the time period. If the lagged coefficient of vector in equation (5) is significant but that of vector of in equation (6) is not significant then the results imply that there is unidirectional causality from exchange rate to stock price retur ns. However, if the lagged coefficient vector in equation (6) is statistically significant but the lagged coefficient vector in equation (5) is not statistically significant then the results imply that there is unidirectional causality from stock prices returns to exchange rate returns. Moreover, if the lagged coefficient vectors of both equations (5 and 6) are statistically significant then the results imply that there is a bidirectional causality from the stock returns and exchange rate returns. Finally, if both lagged coefficient vectors are statistically insignificant, then this implies that there is no causality between these variables. 3.5 Vector Error Correction Model (VECM) According to Engle and Granger (1987), the VECM is a preferable model to the VAR in equations (5 and 6) if it is found that there is cointegration relation between and or among the data series. The VECM discriminates between both the dynamic short-run and long-run Granger causality. The VECM equations are written as follows: where SI is the stock price, ER is the exchange rate, is the error correction term lagged one period; and are uncorrelated white noise terms. The error correction term () is derived from the long-run cointegration relationship between the variables. The estimates of the error correction term of () also shows how much of the deviation from the equilibrium state is corrected in each short period. To find out the presence of long-run causality between the two data series, one will test for the significance of the coefficient of the error correction term in equations (7 and 8) by employing the t-test. Finally the Wald or F-statistic is used to test for the joint significance of both the error correction term and the various interactive terms in equations (7 and 8). If the lagged coefficient vector of equation (7) is statistically significant but the lagged coefficient vector in equation (8) is not significant then the results imply that there is a unidirectional causality from exchange rate to stock price returns. However, if the lagged coefficient vector in equation (8) is statistically significant but the lagged coefficient vector in equation (7) is not statistically significant then the results imply that there is a unidirectional causality from stock prices returns to exchange rate returns. Moreover, if the lagged coefficient vectors of both equations (7 and 8) are statistically significant then the results imply that there is a bidirectional causality from the stock returns and exchange rate returns. Finally, if both lagged coefficient vectors are statistically insignificant, then this implies that there is no causality between the se variables. 3.6 Lag Length selection Criteria To estimate the VAR/VECM model requires choosing the lag length that reduces the information loss. Thus, choosing the lag length involves neutralizing the trade-off between adding more lags against the marginal benefit of additional estimation uncertainty. Thus, too many lags included in the model will lead to additional estimation errors and whiles too few lags may leave out potentially valuable information. To contain this problem, there are so many models to use to select the lag order, namely the Akaike Information (AIC) and Bayes Information Criteria (BIC). I use the BIC to determine the lag order to the estimate model and therefore I will discuss it briefly. The BIC and AIC are expressed as follows: (9) (10) where SSR(p) is the sum of squared residuals of the estimated AR(p). The BIC estimator of , is the value that minimizes BIC(p) out of the range of lags available. The SSR decreases as more lags are introduced, however the second term increases as more lags are introduced. Moreover, the amount of penalty in the second term of the AIC is relatively smaller to that of the BIC. Thus, the BIC awards more penalty factor relative to the AIC. This implies that BIC gives a consistent estimate of the true lag length unlike the BIC. This makes the BIC preferable to AIC which tends to overestimate the lag order with positive probability. Thus, the second term of the AIC is smaller compared to the BIC. 3.7 Test for Structural Breaks To test for structural breaks in the regression coefficients, I estimate an autoregressive distributed lag (ADL) with dummy variables to represent the periods before and after the redenomination of the cedi. Moreover, to choose the appropriate lag length for both the dependent and independent variables to include in the ADL, I estimate the regression equations with different lag lengths and compare the resulting BICs. In effect, the lag length that resulted in the lowest BIC is chosen to estimate the ADL and then the structural break test is conducted. The ADL is estimated as below: where SIt = stock price returns ERt = exchange rate returns Dt = Dummy variable where Dt = 1 if t à ¢ÃƒÆ' ¢Ãƒ ¢Ã¢â‚¬Å¡Ã‚ ¬Ã‚ °Ãƒâ€šÃ‚ ¥ 3 July, 2007; Dt = 0 if t à ¢ÃƒÆ' ¢Ãƒ ¢Ã¢â‚¬Å¡Ã‚ ¬Ã‚ °Ãƒâ€šÃ‚ ¤ 3 July, 2007 à ¢ÃƒÆ'†¹Ãƒ ¢Ã¢â€š ¬Ã‚  ÃƒÆ' ¢Ãƒ ¢Ã¢â‚¬Å¡Ã‚ ¬Ãƒâ€šÃ‚   = difference operator T = time period; d, are the coefficients of the parameters Chow (1960) model test s for structural break in which case the break dates must be known a priori and the decision is made on the F-statistic that tests the null hypothesis of no break; against the alternate hypothesis that at least one of d is nonzero. Thus, in case of the Chow (1960) test, the investigator has to pick an arbitrary break date or pick a known date based on the feature of the data series. In effect, the results can be highly sensitive to these arbitrary choices and as the true break date can be missed. However, in this study, the break date is identified by the redenomination of the cedi. 3.8 The CUSUM of Squares Test In an attempt to test for the constancy of the variance, I employ the CUSUM of square test Brown et al. (1975). This test is principally based on the square of the residuals on the plot of the quantities. This test involves drawing a pair of critical lines on the diagram which is parallel to the mean value line so that the probability that the sample path crosses one or both critical lines is the significance level. If the sample path stays between the pair of critical lines without crossing any of the two lines, then one can conclude that the variance is constant over the period. However, movement outside of the critical lines implies parameter or variance instability. The CUSUM of squares test is based on the test statistic: (12) where the mean value of is given by: . (13)

Sunday, December 22, 2019

Descriptive Essay - Original Writing - 914 Words

Dreamy I thought. Standing on the corner is a young guy with a smile. I see him here almost every day, so I linger for a while. He tells me his name, and I tell him mine. I m Ester, what s your name? I enquired. My names David .,He replied. We end up talking for a while and I asked him if he had ever left this city. He tells me of all these stories of the places where he s been, the distant lakes and mountains, and in valleys oh so green. I can see it in his eyes, he really has been there, travelled in those distant lands, seen sights beyond compare. I am so honoured just to get to know him, and hear him tell his tales. He makes me laugh and smile, stuff I have never been able to do. I want to go and see the world through†¦show more content†¦I m sure it is because my hearts racing quicker than a train or because my hands are sweatier that the pacific ocean. I felt like a jigsaw puzzle in my heart was complete, but whether this is good or bad I do not know, but honestly , I don t care, I was off to find me and who I think is him, off to find our souls waiting for us to find them. All of a sudden, I saw a dark figure in front of me for about five seconds, but it quickly vanished. I told David but, he didn t believe me and thought I was seeing things. I saw it again, but this time it had increased to twice it is size. My eyes flicker back and forth. Every slight movement or wind caused me to jump. My hand unconsciously clenched into a tight fist. I started to uncontrollably breathe heavily. My mouth was dry and I was unable to swallow. I couldn t make out whether it was a person, animal or shadow. I was so confused and when the figure started to come closer, I was about to scream, but just before I could, he held my mouth and whispered to me, I m here and as long as I am here, you are safe. I took a deep breath and stayed quiet and still. My heart was racing. It was coming closer to me inch by inch. Closer and closer. David, I m scared . He turned me around, pulled my shirt s sleeve up and took something sharp out of his pocket. He held the sharp object up and then slashed it through the middle of my

Saturday, December 14, 2019

Recrystallization of Benzoic Acid Free Essays

Recrystallization of Benzoic acid Chemistry 204-002 Date: 4/9/2011 Hector Ortega Recrystallization is a method used to purify compounds, and this is a very important procedure because compounds are naturally impure. Polarity and solubility play a big role in this experiment and these characteristics are exploited in order to have a crystallization of the desired compound. In this experimented benzoic acid was crystallize using ethanol and water. We will write a custom essay sample on Recrystallization of Benzoic Acid or any similar topic only for you Order Now I chose these solvents based on part C of the experiment (table 1. 1). The compound is too soluble in ethanol but too insoluble in water. Benzoic acid is a polar compound in comparison with ethanol which is a less polar compound. However at low temperatures benzoic acid is insoluble in water. Compounds are soluble in solvents with the same polarity, like dissolves like. Table 1. 1 Benzoic Acid solubility Dissolve Heat Ice H2O No No No Ethanol Yes Yes Yes Hexane No No Acetone Yes Yes Toluene No Yes No The benzoic Acid was dissolved in a very small amount of hot ethanol once dissolved water was added drop wise using a disposable pipet until it got cloudy. Once it reached this point the substance was removed from the steam bed and let cool down at room temperature. It is important to let this cool down slowly so impurities don’t get trapped in between the crystals. After 20 minutes the crystals were filtered out using a vacuum filter method. The crystals were carefully removed from the filter paper and weighted. These crystals were dried out for a period of 2 weeks, to later get a melting point. The MSDS value was compared with the experimental value to verify purity of the crystals Page | 1 Recrystallization of Benzoic acid Chemistry 204-002 Date: 4/9/2011 Hector Ortega Data Collected: Ethanol and Water used as solvents Benzoic acid Grams Started 0. 154 Recovered 0. 126 Final Recovered 0. 064 Percent Recovery 81. 81% *Before Drying for two weeks Final Recovery 41. 52% Melting Point 118. 9 ° C – 119. 9 ° C MSDS MP 122. 4 ° C Percent difference 3. 684% Crystallizing benzoic acid using a mixture of solvents is the most efficient procedure compared to using one solvent alone. By comparing the experimental and MSDS melting points we can see that our recovered crystals had very little impurities only a 3. 8 % difference. If I was to repeat the experiment I would improve the recovery process by letting the substance cool down even more slowly to avoid impurities to get trapped in the crystals. When the crystals were moved from the filter paper to the weighing boat some of the crystals were lost. This could be improved by letting the sample dry longer so the crystals would not stick to the filter p aper or the spatula. Another possible error could have happened when taking the melting point, the rate at which the temperature was rising was a little too high. In the future slowly and gradually rising the temperature would give better more accurate results. Page | 2 Recrystallization of Benzoic acid Chemistry 204-002 Date: 4/9/2011 Hector Ortega 3D embedded Structures  « Che m 3 D E m b e d  » Benzoic Acid  « Che m 3 D E m b e d  » Water Page | 3 Recrystallization of Benzoic acid Chemistry 204-002 Date: 4/9/2011 Hector Ortega  « Che m 3 D E m b e d  » Ethanol References Zubrick (8th ed. ) Chs. 6, 11 and 13 Chemdraw Ultra Version 12. 0 Page | 4 How to cite Recrystallization of Benzoic Acid, Essay examples Recrystallization of Benzoic Acid Free Essays The objective of this experiment was to observe multi-step purification of benzoic acid after performing the extraction from a mixture containing benzoic acid, cellulose, and methyl orange. Recrystallization was done to remove impurities from the sample. The amount of BA recovered during recrystallization is much less than the extracted amount of BA. We will write a custom essay sample on Recrystallization of Benzoic Acid or any similar topic only for you Order Now The difference between the pure and impure samples was observed by comparison of melting points. It was found that impure samples will have a lower and wider melting point range.The experiment performed was important because it provides important knowledge about the chemical nature and reactivity’s of various compounds that can be used in everyday life. Introduction Now that the desired compound is extracted, it still contains impurities. These impurities can be removed through a process called recrystallization. Recrystallization is a method for purifying solid compounds which are frequently the products of organic reactions. This theory is based on three important concepts. The first is that a compound is always more soluble in hot solvents than in cold solvents.Secondly, molecules have unique solubility properties. Lastly, a growing crystal will only accept similar entities into its lattice. This is related to the crystal lattice theory which states crystal formation is anti-entropic based on the equation ? G =? H-T? S. There are three stages of solubility: collision, dissociation, and solvation. In order to raise the probability of collision between the solute and solvent, heat is added to the system. When this occurs, the solute will attack the crystalline structure of the solute and start dissociation. As dissociation continues until all the molecules are free, solvation occurs.Choosing the right solvent is important when considering recrystallization. The solute must have a high temperature coefficient in the solvent: it must be soluble at high temperatures and insoluble at low temperatures, satisfying the first principle stated above. Also the boiling point of the solvent must be lower than the melting point of the solute. This will ensure that the solute dissolves in the solvent and does not melt. The solvent must also be inert to prevent chemical interactions with the solute. Impurities must either be readily dissolved in the solvent or be insoluble.The solvent must also be volatile, and finally, it would be beneficial to the experimenter if the solvent is relatively inexpensive. Once the color and most impurities are removed, the crystals can be formed in the solution through a process called nucleation. Nucleation can be induced by slowly cooling the solution to room temperature. It is important to do this slowly so that small solute resembling impurities do not enter the crystal lattice, as described by the third principle of recrystallization. Chemists often add already pure crystals of the solute to the solution in order to provide a pre-formed lattice for other molecules to enter. This is called seeding. Scratching the glass container in which the solution is contained with a glass stir rod will also induce nucleation on microscopic glass particles. The concept of scratching is similar to that of seeding. Finally, nucleation can be induced by cooling the solution farther in an ice bath; however, this is only a last resort option due to its least efficiency to bring forth crystals. The crystallized solute can then be collected by vacuum filtration. There is a difference observed in the physical properties of the pure compound and the impure mixture. One of the tests of purity is melting point. Melting point is an intrinsic, or intensive, property; the value is independent of the quantity of the substance. Melting point is the temperature at which a substance changes physical state from solid to liquid. Because the substance will have a certain shape and surface area exposure, there will be a time interval in which the melting occurs. Thus, it is more accurate to refer to this as melting range. Melting range encompasses the temperature at which the first particles can be seen turning from solid to liquid until all the sample is in the liquid state. Purer samples have smaller melting ranges.Perfectly pure compounds will have ranges of only 1-2 °C. Impurities lower melting point below literature values and also widen the range between which melting occurs. New techniques and equipment used were used during both parts of the purification process. Activated charcoal was used to adsorb impure colored products. Gravity filtration was used to remove insoluble products which were impurities. Fluted filter paper was used to catch more of the impurities. A heating mantel was introduced during recrystallization. It is a heat source used for solutions. For determining the melting point of benzoic acid, a Mel-Temp apparatus was use.It is used for determining when a small amount of a solid begins to melt and when the melting ends while recording the temperatures, respectively. Experimental: Recrystallization Lab: Initially, took a small amount of impure BA to the side for following week’s lab. The impure BA crystals were weighed, using an analytical balance, and then placed in a 250 mL Erlenmeyer flask. 200 mL of water was boiled (with boiling stones) in a 250 mL round bottom flask using a heating mantel. The boiled water was added slowly to the benzoic acid crystals. Only enough water was added to dissolve the BA crystals. For the rest of the lab the Erlenmeyer flask was kept on a steam bath. Charcoal was added to the BA solution and then gravity filtered using a funnel with fluted filter paper. The filtrate was collected in a 250 mL Erlenmeyer flask. If color in the BA solution still remained then charcoal should be added again. The BA solution was removed from the steam bath and cooled, preferably on a window sill. If crystals did not form while cooling on window sill, use another method to induce nucleation to the start the formation of crystals. The crystals were collects by vacuum filtration and placed on a watch glass to dry. Melting Point of Benzoic Acid: A melting point tube was loaded with BA crystals by inverting the tube into the BA crystals on the watch glass. The tube was packed by dropping through a funnel. The Mel-Temp apparatus was used to determine the melting point range. A rapid melting range experiment was done first and then a slow melting range experiment was carried out to get a better range. Results: Recrystallization lab: Observations: Not much charcoal was used to adsorb the colored molecules The BA crystals were small, shiny, flaky, and white. Almost comparable to texture of dandruff. Data: Mass of extracted Benzoic Acid = 2. 3 g Mass of recrystallized Benzoic Acid = 1. 84 g Calculations: Percent (%) recovery =(weight after recrystalization)/(mass crude BA) ? 100 Percent (%) recovery =(1. 84 g)/(2. 43 g) ? 100=75. 72% Melting Point lab: Observations: Once the benzoic acid began to melt, it happened very quickly.It was hard was difficult to watch the melting and recording the start and end temperature. The crude BA had a lower and wider melting point range. Data: Melting Point Ranges RunCrude (Impure) Benzoic Acid ( °C)Purified Benzoic Acid ( °C) Fast 110. 2-118. 4 at 4. 5 selectivity (Range: 8. 2)115. 4-118. 5 at 4 selectivity(Range: 3. ) Slow113. 2-117. 3 selectivity (Range:4. 1)117. 5-120. 0 selectivity (Range: 2. 5) Discussion ; The goal of recrystallization and determining melting point labs were to explore the techniques used to obtain pure samples from desired compounds. After the extraction the goal was to recrystallize the benzoic acid and determine the percent recovery. Then the goal was to determine the melting point range of the recrystallized benzoic acid and compare it to the melting range of the small sample of the impure benzoic acid. 1. 84 grams of pure benzoic acid was obtained, which was calculated to be 75. 2% from the 2. 43 grams of impure benzoic acid.The percent recovery from the impure sample shows that about three fourths of the sample was able to be collected as pure benzoic acid, and that 0. 59 g of the impure benzoic acid was impurities. From this the experimenter can infer that the pure benzoic acid accounted for most of the mass or that little benzoic acid was lost with the removal of the impurities. Also, there is always a chance that some of the benzoic acid may have remained in the solution instead of crystallizing. Also, using an ice-bath to induce nucleation could have lowered my results or recrystallization because it was the last resort to crystalize the solute. Maybe adding too much charcoal could have adsorbed some of the solute. The charcoal was used to adsorb any of the cellulose (which is the reason for the color) that was left behind. Not too much charcoal was actually used; however, my benzoic acid solution did not have much color so charcoal may not have been needed. Note that the initial value for percent recovery is slightly less than the extracted mass because of the impure benzoic acid set aside for the melting point comparison. The total composition from the very first starting benzoic acid mixture is only 44. 2% (1. 84 grams / 4. 17 grams). Considering practical purposes of recrystallization, one comes to realize how important it is to make this processes as efficient as possible to save money and gain as much product as possible, for example with ibuprofen purification for the pharmaceutical industry. The purity of the sample is shown by the melting range. As expected, the pure benzoic acid had the smallest melting point range of 2. 5 °C. From this, one can tell that this sample was not perfectly pure because pure compounds have melting point ranges of less than 1 °C.There may have been some impurities left in the sample since activated charcoal was not used for this sample. Human error while scraping the impure mixture from the funnel and also from the Erlenmeyer flask would result in a decreased yield. Also, the nucleation may have had some impurity particles collect in the lattice when recrystallizing. After performing the rapid and slow experiment, the temperatures (especially for the pure BA) were not similar. This was probably due to what is called thermometer lag. If the Mel-Temp apparatus’ selectivity was higher than the temperature readings were not as accurate as the slow experiment.The actual value for the melting range coincides with the literature value of 122. 4 °C given in the reagent table. The impure sample, however, had a significantly larger melting range of 4. 1 °C. Also, the impure sample had a lower temperature. This is because impurities disrupt lattice forces and decrease the energy required to break the intermolecular bonds between benzoic acid molecules. One way that this experiment could have been improved is to have more space to perform the various steps in the lab. A lot of the mistakes and errors committed (i. e. pillage) were due to crowding of various equipment that were closely packed next to each other. Overall, theses labs were a success be the experimenter was able to achieve the goals of each lab. The benzoic acid was able to recrystallize and the melting point was fairly close to the literature value even with possible errors performed in lab. Works Cited Wikipedia: The Free Encyclopedia. Wikimedia Foundation, Inc. 22 July 2004. Thurs. 7 Oct. 2010. Zubrick, James. The Organic Chem Lab Survival Manual. 6th. Pittsburgh: John Wiley Son, Inc. , 2008. Print. How to cite Recrystallization of Benzoic Acid, Papers Recrystallization of Benzoic Acid Free Essays Recrystallization of Benzoic Acid Objective To purify benzoic acid by recrystallization and gain experience with a basic organic laboratory techniques. Background Products of chemical reactions are often contaminated with impurities. One method for purifying chemicals, recrystallization, takes advantage of the differences in the solubilities of the desired products and the impurities and the tendency for the slow formation of crystals to exclude impurities from the crystalline solid. We will write a custom essay sample on Recrystallization of Benzoic Acid or any similar topic only for you Order Now HC HC HC CH C CH MgBr + CO2 + HCl HC HC HC CH C CH CO2H ClMgBr Benzoic acid, the chemical that we will be purifying, can be made by reacting phenylmagnesium bromide with carbon dioxide. When the product of that reaction is treated with hydrochloric acid, benzoic acid is formed. From the balanced chemical equation, it is clear that the benzoic acid will not be pure since the byproduct MgClBr, an ionic solid, forms at the same time the desired product forms. Benzoic acid can be separated from ionic solids because the materials have different solubilities in water. At room temperature, benzoic acid is not particularly soluble in water, whereas ionic solids like MgClBr are. Thus, adding water to the crude reaction products will dissolve the ionic solid, and nearly all of the benzoic acid will remain undissolved. If the suspension were filtered, much of the impurity would be washed away; however, the resulting product wouldn’t be as pure as a recrystallized product. To take advantage of the extra purity garnered by crystallization, all of the benzoic acid must be dissolved. On the other hand, the benzoic acid needs to come back out of solution to crystallize. Simply adding room-temperature water cannot accomplish this goal; once the benzoic acid is dissolved there would be no reason for it crystallize. Since benzoic acid is much more soluble in hot water as compared to cold, small amounts of hot water are added to dissolve the benzoic acid. If the hot, saturated, aqueous solution of benzoic acid is cooled, the solution becomes supersaturated, and the supersaturated solution crystallizes. Procedure 1. Obtain a sample of copper(II) sulfate contaminated benzoic acid. 2. Add approximately 0. g (record the actual mass) of the contaminated benzoic acid and 5 mL of water to a 25-mL Erlenmeyer flask. 3. Warm the flask and its contents on a hot plate and slowly add near-boiling water to dissolve the solids. 4. Continue to warm the flask and add near-boiling water until all of the solids have disolved 5. Remove the flask from the hot plate and allow it to cool slowly on the bench top. Covering the flask with a beaker can help slow the rate at which the solution cools. After approximately twenty minutes, crystals will have formed. Cool the suspension further using an ice bath. If crystals have not formed after 20 minutes, there are a few techniques that can be used to coax the crystals out of solution. Often scratching the glass container with a glass rod will induce crystallization. Alternatively, a seed crystal can be obtained by evaporating a drop of the solution on the tip of a stirring rod or spatula. Returning this seed crystal to the super saturated solution will cause crystals to form. 6. Transfer the crystals to a Hirsch funnel, and filter the benzoic acid–water suspension. . Wash the benzoic acid crystals with ice-cold water by pouring ice-cold water over the crystals. 8. Dry the crystals on the Hirsch funnel; that is, allow the vacuum filtration system to draw air through the crystals until the mass of the crystals remains relatively constant. Place the benzoic acid in your drawer and allow it to dry completely. 9. While the benzoic acid is drying, evaporate the water from the aqueous CuSO4 s olution. Remember to add a magnetic stir bar to your flask to lower the risk of spattering. 10. Note the appearance of your CuSO4, and, if possible, record the mass of the CuSO4 that you obtained. 11. After allowing the benzoic acid crystals to dry for a week, determine the mass and the melting point of the benzoic acid. Experimental Report Write an â€Å"experimental† describing the procedure that you followed to recrystallize the benzoic acid. A first draft of the experimental is due one week after steps 1–10 have been completed. A final copy that includes the final mass and the melting point of the benzoic acid is due one week after step 11 is completed. How to cite Recrystallization of Benzoic Acid, Papers

Friday, December 6, 2019

Heart Of Darkness (3810 words) Essay Example For Students

Heart Of Darkness (3810 words) Essay Heart of DarknessHeart of DarknessConrads novel, Heart of Darkness, relieson the historical period of imperialism in order to describe its protagonist,Charlie Marlow, and his struggle. Marlows catharsis in the novel, as hegoes to the Congo, rests on how he visualizes the effects of imperialism. This paper will analyze Marlows change, as caused by his exposure tothe imperialistic nature of the historical period in which he lived. Marlow is asked by the company, the organizationfor whom he works, to travel to the Congo river and report back to themabout Mr. Kurtz, a top notch officer of theirs. When he sets sail, he doesntknow what to expect. When his journey is completed, this little tripwill have changed Marlow forever!Heart of Darkness is a story of one mansjourney through the African Congo and the enlightenment of his soul. It begins withCharlie Marlow, along with a few of his comrades, cruisingaboard the Nellie, a traditional sailboat. On the boat, Marlow begins totell of his experiences in the Congo. Conrad uses Marlow to reveal allthe personal thoughts and emotions that he wants to portray while Marlowgoes on this voyage of a lifetime. Marlow begins his voyage as an ordinaryEnglish sailor who is traveling to the African Congo on a business trip. He is an Englishmen through and through. Hes never been exposed to anyalternative form of culture, similar to the one he will encounter in Africa,and he has no idea about the drastically different culture that existsout there. Throughout the book, Conrad, via Marlowsobservations, reveals to the reader the naive mentality shared by everyEuropean. Marlow as well, shares this naivete in the beginning ofhis voyage. However, after his first few moments in the Congo, he realizesthe ignorance he and all his comrades possess. We first recognize the generalnaivete of the Europeans when Marlows aunt is seeing him for thelast time before he embarks on his journey. Marlows aunt is under theassumption that the voyage is a mission to wean those ignorant millionsfrom their horrid ways(18-19). In reality, however, the Europeans arethere in the name of imperialism and their sole objective is to earn asubstantial profit by collecting all the ivory in Africa. Another manifestation of the Europeansobliviousness towards reality is seen when Marlow is recounting his adventureaboard the Nellie. He addresses his comrades who are on board saying:When you have to attend to things of thatsort, to the mere incidents of the surface, the reality-the reality I tellyoufades. The inner truth is hidden luckily, luckily. But I felt itall the same; I felt often its mysterious stillness watching over me atmy monkey tricks, just as it watches you fellows performing on your respectivetight ropes forwhat is it? half a crown a tumble(56).What Marlow is saying is that while heis in the Congo, although he has to concentrate on the petty little everydaythings, such as overseeing the repair of his boat, he is still aware ofwhat is going on around him and of the horrible reality in which he isin the midst of. On the other hand, his friends on the boat simply dontknow of these realities. It is their ignorance, as well as their innocencewhich provokes them to say Try to be civil, Marlow(57). Not only are they oblivious to the realitywhich Marlow is exposed to, but their naivete is so great, theycant even comprehend a place where this so called reality would evenbe a bad dream! Hence, their response is clearly rebuking the words ofa savage for having said something so ridiculous and uncivilized. Quite surprisingly, this mentality doesnot pertain exclusively to the Englishmen in Europe. At one point duringMarlows voyage down the Congo, his boat hits an enormous patch of fog. At that very instant, a very loud cry is let out(66). After Marlow looksaround and makes sure everything is all right, he observes the contrastsof the whites and the blacks expressions. It was very curious to see the contrastof expression of the white men and of the black fellows of our crew, whowere as much strangers to this part of the river as we, though their homeswere only eight hundred miles away. The whites, of course greatly discomposed,had besides a curious look of being painfully shocked by such an outrageousrow. The others had an alert, naturally interested expression; but theirfaces were essentially quiet. . . (67). Once again, we see the simple-mindednessof the Europeans, even if they were exposed to reality. Their mentalityis engraved in their minds and is so impliable, that even the environmentof the Congo cant sway their belief that people simply dont do the horriblethings Marlow recounts. The whites are dumbfounded and can not comprehendhow people, in this case the natives, would simply attack these innocentpeople. That would just be wrong! The blacks, however, who are cognizantof the reality in which they live, are essentially quiet. They feel rightat home, and are not phased by the shriek. Similarly, the difference of mentalitiesis shown when Marlow speaks of the portion of his crew who are cannibals. While in themidst of his journey, Marlow, quite casually, converses withthese cannibals; even about their animalistic ways! As Jacques Berthoudsaid so accurately in his Joseph Conrad, what would be nspeakable horrorin Londonbecomes, on the Congo river, an unremarkable topic of conversation(47). These unspeakable horrors are hardly unspeakable in the Congo becausethey are normal occurrences there. On the Nellie, Marlow explains to his comrades,the basic difference between living in Europe, and being in the Congo. He states:You cant understand. How could you? Withsolid pavement under your feet, surrounded by kind neighbors ready to cheeryouor to fall you, stepping delicately between the butcher and the policeman,in the holy terror of scandal and gallows and lunatic asylumshow canyou imagine what particular region of the first ages a mans untrammeledfeet may take him into by the way of solitudeutter solitude withouta policemanby the way of silence utter silence, where no warning voiceof a kind neighbor can be heard whispering of public opinion(82)?In Europe, there are kind neighbors whoare there to make sure that everything is all right. The European liveshis life stepping delicately between the butcher and the policeman. Everywherehe looks, there is always someone there who can catch him if he is falling. On the other hand, once a man enters the Congo, he is all alone. No policeman,no warning voice of a kind neighborno one!It is now when Marlow enters the Congoand begins his voyage, that he realizes the environment he comes from isnot reality, and the only way he is going to discover reality is to keepgoing up the river There is one specific theme in Heart ofDarkness in which the reader can follow Marlows evolution from the everydayEuropean to a man who realizes his own naivete and finally to hisuncovering of his own reality. This evolution comes about as a direct resultof Marlows observations of how things are named. This sounds very unusual,that a man would find his true reality by observing the names of certainthings. However, it is precisely these observations which change Marlowforever. Marlow first realizes the Europeans flaw of not being able togive something a name of significance, in the beginning of his voyage,when he has not quite reached the Congo, but he is extremely close. Once, I remember, we came upon a man ofwar anchored off the coast. There wasnt even a shed there, and she wasshelling the bush. It appears the French had one of their wars going onthere-abouts. Her ensign dropped like a limp rag; the muzzles of the longsix inch guns stuck out all over the low hull; the greasy, slimy swellswung her up lazily and let her down, swaying her thin masts. In the emptyimmensity of earth, sky, and water, there she was, incomprehensible, firinginto a continent. Pop, would go one of the six inch guns; a small flamewould dart and vanish, a little white smoke would disappear, a tiny projectilewould give a feeble screechand nothing happened. Nothing could happen. The Career that interest me is being a doctor. EssayNo; you want a deliberate belief. An appeal to me in this fiendish rowisthere? Very well; I hear; I admit, but have a voice too, and for good orevil mine is the voice that can not be silenced (60).This is the lesson which Marlow has learned. Objective standards alone will not lead one to recognize the reality insomething. One can not only depend on anthers principles to find his realityin something because they have not had to bear the pain and responsibilityof creating it. Principles are usually acquisitions, which like other thingswe acquire rather than generate, like clothes are easily shaken off. Thepower of speech which will sustain a man is the power to create or affirmfor ones self a deliberate, or a chosen belief (Bruce Johnson. 79). This judgment must be from ones own internalstrengths. That is why Marlow says, for good or evil, mine is the speechthat can not be silenced. As Kurtz has taught him with his own judgment,a judgment of truth overpowers morality. To find ones own reality, onemust not rely solely on other peoples morality, others peoples principlesand he must assess his own life. What Kurtz did is that he showed thatregardless of whether the truth is good or bad, one must face up to hisreality. He must face up to his own actions even when the conclusion isthe horror, and by doing so, he will find his true reality. Marlow understands that being true to yourselfis not following anthers moral code, but being able to judge ones selfhonestly and uncover their own reality. It is because of this understandingthat Marlow claims that Kurtzs last words is a moral victory paid forby innumerable defeats(120). Despite Kurtzs immoral ways, he is victoriousbecause he didnt run away from the truth; and that is his moral victory. He is true to himself.!On his voyage, Marlow notices at one ofthe stations, a picture that Kurtz had drawn when he was there. It is asketch in oils on a panel representing a woman draped and blindfolded,carrying a lighted torch. The background was sombrealmost black(40). At the time, Marlow didnt really know what it meant. However, this isa precise representation of Kurtz himself. Firstly, the background wassombrealmost black. This is a manifestation of Kurtz because his lifeis full of darkness. He kills, he steals, and he is worshipped as a god. Kurtz cannot be without blackness and survive. In addition, the picturedisplays the lesson itself. It is a picture of the lady of justice holdinga torch. This is Kurtzs role. Unlike Europe, which imposes their principlesupon others, he is merely there to illuminate(79). Kurtz is there toexpand the peoples minds, to introduce them to a broad new spectrum ofreality. However, he does not impose his own reality upon them. Hence,he is blindfolded in the picture. To him, they make a subjective decisionand they find their own truth, regardless of what that truth may be. Thatis his lesson. Eventually Marlow realizes that Kurtzspicture was in essence, a self portrait. The same thing which Kurtz conveyedwith the horror, he conveyed with this picture. Marlows realizationis evident with this remark. I dont like workno man doesbut I likewhats in the workthe chance to find yourself. Your own realityforyourself, not for others(47). Marlow learns the essence of naming andunderstands what it means to be yourself. However, Marlow has encounteredtwo extremes. The European mentality, which is completely oblivious toreality, and Kurtz, a man who has found his reality, but it is one of horrorand no restraint from any wrongdoing. He is now returning to his home todeal with his former world, however, he now possesses his new understanding. Marlow cannot return to his previous European ways simply because hehas been enlightened and lost his naivete. However, why cant he adapt Kurtzs waysand live the other extreme? At one point, Marlow had peeped over the edge(119). Why didnt he jump over? Marlow is repelled from joining Kurtz for severalreasons. Firstly, Kurtz had kicked himself loose from the earthhe hadkicked the earth to pieces. He was alone, and I before him didnot know whether I stood on the ground or floated in the air(112). Kurtzhad denied any sort of moral convictions in order to be worshipped as agod. Because of this unmonitered power, Kurtz lost all sense of restraintand became the savage that he was. Marlow, however, has not lost his senseof morality. What Marlow rejected in Kurtz was the complete absence inKurtz of any innate or transcendental sanctions (Johnson. 99). It is because of Marlows rejection ofboth the Europeans, who Marlow claims are full of stupid importance,and of Kurtzsinability to establish his own moral code, that Marlow choosesan alternative reality(Berthoud. 60). The first time the reader witnessesMarlows choice and becomes a centrist, is when he first gets back to Europe. Marlow finds himself resenting the way the Europeans went about their life,hurrying through the streets to filch a little money from each other(120).Notonly did he find their lives meaningless, but he mocked them to himself. I had no particular desire to enlighten them, but I had some difficultyrestraining myself from laughing in their faces so full of stupid importance I tottered about the streetsgrinning bitterly at perfectly respectablepeople. I admit my behavior was inexcusable (120). Although Marlowlooked down upon these Europeans, he says something remarkable. He judgedhis own actions and found them inexcusable. This is his manifestationof breaking away from Kurtzs extreme. Unlike Kurtz who lacked all restraintand would never find looking down on people bad, Marlow realized that hecouldnt hold it against them simply because they didnt know better. Clearly,Marlow is edging toward a middle ground. Despite this act of judgment, the readerdoesnt know exactly where Marlow stands. However, Marlow does somethingthat is the quintessential act of affirmation that he has chose the middleof the two extremes. While aboard the Nellie, Marlow tells his comradesthat I hate, detest, and cant bear a liesimply because it appallsme. There is a taint of death, a flavor ofmortality in lies(44). Towards the end of the novel, Marlow is invitedby Kurtzs fiancee to go to her house to speak of her beloved Kurtz. Uponher asking Marlow what his last words were, Marlow responded The lastword he pronounced wasyour name(131). He lies to her. He does somethinghe utterly detests. This is the event that convinces the reader of Marlowsuptaking of a middle position. He does look inside himself and use hisown personal ability to judge this event. He does what Kurtz had told him. Despite his abhorrence of lies, he judges this situation and decides thatit was right to lie. However, he is different from Kurtz. Kurtz did judgeevery event independently, however, he does it solely based on his ownwhims. He could not incorporate any objective principles whatsoever inmaking his decision. Marlow does judge every event independently, however,he can not rely solely on his own creeds. Regardless of his decision, hewill always incorporate some objective principles into his judgment. Marlownow creates his alternative reality and achieves his truth. When Marlow was exposed to the imperialisticenvironment of the congo, it had a tremendous effect upon him. The protagonistof Conrads novel undergoes a drastic change in response to his environment,common only to that specific time period. Kurtz shows Marlow the flawsin the Europeans imperialistic ideals. Kurtz sees the meaninglessness ofEuropean standards of the time, and therefore changes his entire perceptionand behavior.