Determination of Vitamin C Concentration by Titration

Determination of Vitamin C Concentration by Titration Vitamin C (Ascorbic acid) is a necessary nutrient in the human diet. Fruit juices are among the most common consumer items taken to meet our daily requirements of ascorbic acid. Vitamin C can be determined in food by use of an oxidation-reduction reaction. The redox reaction is preferable to an acid-base titration because a number of other species in juice can act as acids, but relatively few interfere with the oxidation of ascorbic acid by iodine. This method determines the vitamin C concentration in a solution by a redox titration with potassium iodate in the presence of potassium iodide. The excess iodine is back titrated with thiosulfate (S2O32-). Starch solution is used as indicator. Iodide ions reduce iodate ions producing iodine in an amount equivalent to the iodate. The principal reactions involved are shown by the following equations. Generation of iodine: IO3- + 5I- + 6H+ → 3I2 + 3H2O Titration of iodine with thiosulfate: I2 + 2S2O32- → 2I- + S4O62- The reaction of iodine with ascorbic acid is shown in the following equation: C6H8O6 + I2 → C6H6O6 + 2I- + 2H+ Ascorbic acid is oxidized to dehydroascorbic acid EXPERIMENT Apparatus burette (50 mL), volumetric flasks (250 mL, 100mL), beaker (400 mL), pipette ( 10 mL, 25 mL), Erlenmeyer flasks (250mL) Reagents oxalic acid, C2H2O4.2H2O, potassium iodate KIO3, sodium carbonate, Na2CO3, sodium thiosulfate pentahydrate, Na2S2O3.5H2O, sulfuric acid, H2SO4, potassium iodide, KI, starch indicator solution (2% w/v in distilled water), apple juice Preparation of Na2S2O3 and KIO3 solution Na2S2O3.5H2O and Na2CO3 were weighed 1.8613 g and 8 mg respectively to prepare exactly 250 mL of 0.03M sodium thiosulfate solution. Dilution of 0.25 g KIO3 in 250 mL volumetric flask was done. Standardization of Sodium Thiosulfate 2 g of KI and 10 mL of 0.6M H2SO4 were added into 250 mL Erlenmeyer flask after 25 mL of KIO3 was pipette. This solution was titrated with sodium thiosulfate solution until the initial brown color of the solution turns to pale yellow. 2 mL of starch indicator was added and the titration was completed at the disappearance of the blue color. Titration was repeated 2 times. Preparation of sample 0.1 gm of oxalic acid was added into 50 mL of apple juice after it was pipette then the sample juice was diluted in a 100 mL volumetric flask. Titration of sample 2 g of KI and 10 mL of 0.6M H2SO4 were added into Erlenmeyer flask after 25 mL of KIO3 and 25 mL of diluted sample were pipette. The solution was titrated with standard Na2S2O3. 2 mL starch indicator was added just before the end point. The titration was repeated 2 times. RESULT AND DISCUSSION The molar concentration of standardize solution and vitamin c studied are shown in summary data report sheet and the all calculations are shown in appendixes. Volumetric analyses based on titrations with reducing or oxidizing agents are very useful for many determinations one of the example is iodometry titration. It was performed using visual indicator that is starch indicator to determine the end point. Starch forms a not very reversible complex with I2 that is a very dark-blue color. The color reaction is sensitive to very small amounts of iodine. Iodine is a moderately strong oxidizing agent and a weak reducing agent. When an excess of iodide is added to a solution of an oxidizing agents, I2 is produced in an amount equivalent to the oxidizing agent present. This I2 can therefore, be titrated with a reducing agent and the result will be the same as if the oxidizing agent were titrated directly. The titrating agent used is sodium thiosulfate. The oxidizing agent not directly titrate with the thiosulfate because strong oxidizing agents oxidize thiosulfate to a oxidation states higher than that of tetrathionate. The end point is detected with starch. The starch is not added in the beginning of the titration when the iodine concentration is high. Instead, it is added just before the end point when the dilute iodine color becomes pale yellow. The reason for using acid is that reactions between many oxidizing agents and iodide are promoted by high acidity. Sodium thiosulfate solution is standardized iodometrically against a pure oxidizing agent that is KIO3. from the volume of titrant used to titrate the primary standard, the molar concentration of the titrant can be calculated. The calculations that involve in these data are base on volumetric analysis which consists of titration and standard solution that means need stoichiometric calculations. The data of standardization of thiosulfate in term of volumes sodium thiosulfate have low accuracy because the differentiation between readings quite obvious compare to volumes of sodium thiosulfate in determination of vitamin C. The data of the experiment is compared to the true data. The true data state that the content of vitamin C mg per 100 mL is 15 mg but in the experiment is 0.8096 mg / 100 mL. This is because the vitamin C is decompose by heat. The diluted sample is prepared too earlier. There are several errors that might be occurred in this experiment. One of that is systematic error which means error in burette reading. The sources of systematic error consists of three types ; instrument error, method error, and personal error. Personal error occurred to the operator of equipment especially in sensitivity in color changes. For example in this experiment the color changes involve is brownish to pale yellow. Whereas the method error occurred when the reaction does not complete. Even the instrument also can cause the error especially when the end of burette and pipette are blocked by something. Instrument errors can minimize by good maintenance of equipment. To observe the color changes when do titration in analyte put the plain white paper at the bottom of conical flask. When taking burette reading always read at the meniscus and the reading of pipette as well. The error in data can be overcome by applying statistical tests on data for example find the standard division and mean. To apply this test carries out replicate measurements. In this experiment we do triplicate. CONCLUSION The molarity of KIO3 is 4.6728 x 10-3 M. The molarity of standardize thiosulfate is 0.0278 M and the content of vitamin C in mg/100 mL is 0.8096.

The Cyclic Relationship Between Culture And Technology :: Environment Environmental Pollution Preservation

Trying to determine the effect of culture on technology is a difficult task. This is due to the cyclic nature of the relationship between culture and technology. Working with the general notion of culture (1), it is easy to see why the task of analyzing the effect of culture on technology is hard. This is because technology itself is part of this definition of culture, â€Å"all other products of human work and thought† (2). In a sense, we are trying to find the effect of culture on culture itself, which initially sounds strange. However, considering technology as one of the venues that a given culture utilizes to transform itself, the challenge to examine the effect of culture on technology can be narrowed down to the investigation of the cyclic relationship between culture and technology. Thus, this paper discusses, what we will label, ‘technology-induced cultures’ and ‘culture-induced technologies’, in order to show the feedback loop between cultur e and technology. The class readings provide several instances of how technology affects and transforms its encompassing culture (i.e. the culture that was responsible for bringing forth the very same technology). One such technology is agriculture. The hunting and gathering way of life was already being saturated when the world population was about 4 million. With human population reaching 200 million by 200 B.C., it would have been difficult, if not impossible, to survive by just gathering and hunting. (3). Even though it is hard to claim that early man consciously pursued agriculture as the solution to this problem, it is uncontested that the hunter-gatherer society is the culture that was responsible for the invention of agriculture, as Ehrlich points out, â€Å"agriculture was thus invented gradually, piecemeal, and quite probably sometime reluctantly as groups changed time-honored lifestyles†(Ehrlich 15/26). The effect of this technology on the hunter-gatherer society was phenomenal, as it â€Å"put humanity on the road to sociopolitical complexity†(Ehrlich 17/26). The constant mobility as well as the scarce resources involved with the hunting and gathering way of life did not allow for the development of a complex society, as Ehrlich explicitly mentions, â€Å"Without the ensuring agricultural revolution and the sedentary life and divisions of labor it eventually made possible, cultural evolution could never have produced our complex modern civilization. Without farming, which freed some people of the chore of wrestling nourishment from the environment, there would be no cities, no states, no science, and no mayors†(4).

Essay --

Myocardial infarction is defined as pathological myocardial cell death due to a prolonged interruption of the blood supply to the heart, leading to a permanent loss of cardiomyocytes (Kristian Thygesen et al., 2012). The impact of myocardial infarction brought about a cascade of events followed by scar formation conferring protection to the insulted heart from being ruptured due to high pressure. Although it offers cardiac protection, scar tissues are instead acellular and lack the normal biochemical properties of cardiac cell, thus enhancing the possibilities of disrupting the contractile function of the heart. These then may eventually leads to the depressed left ventricular (LV) systolic and diastolic function of the injured heart (Joggerst & Hatzopoulos, 2009). Heart, has been considered as a terminally differentiated organ with an almost absent self-regenerative capacity back in the early days. The dogma was then broken by the findings documented on the presence of a small cluster of a clonogenic endogenous cardiac stem cell pooling within the heart. These cluster of endogenous cardiac stem cell demonstrates self-renewal capacity and multi-lineage differentiation potential suggesting that heart possess own intrinsic repair mechanism (Antonio P. Beltrami et al., 2003; Bearzi et al., 2007; Ellison, Nadal-Ginard, & Torella, 2012; Koudstaal et al., 2013). However the number of the endogenous cardiac stem cell is too low, rendering the self-repair mechanism to fail (Beltrami et al., 2001). Stem cell based therapy holds promise in participating in the myocardial regeneration replacing the lost functional cardiomyocyte in the damaged myocardium. The roles of bone marrow stem cell transplantation in myocardial therapy too, have long... ... outcome of cardiac therapy. The main idea behind this novel therapeutic approach is the possibility to constrain the limitations of the administration of stem cells in stem cell-based therapy. Taking the advantage of the conditioned medium and the benefit of paracrine signaling factors in promoting endogenous cardiac repair mechanism, we are trying to look at the best culture conditioned in terms of cell seeding density, glucose concentration, serum replacement and incubation time in order to generate conditioned medium that employs a potent paracrine signaling action that might enhance the ex vivo expansion of cardiac stem cell and potentially to be marketed as an ‘off-the-shelf’ cardiac stem cell culture medium in the near future. Yet, more effort should be considered carefully before this novel noninvasive idea is implemented in a more complex clinical setting.

If I Were a Poor Black Kid

English 112 20 February 2013 If I were a poor black kid Gene Marks is a contributor to Forbes and the author of the article, â€Å"If I were a poor black kid. † In the beginning of his article he agrees with Mr. Obama and quotes the president’s statement, â€Å"This is the defining issue of our time†¦This is a make-or-break moment for the middle class, and for all those who are fighting to get into the middle class. Because what’s at stake is whether this will be a country where working people can earn enough to raise a family, build a modest savings, own a home, secure their retirement. It is hard not to agree with the president and Mr. Marks that these are important times for the middle class. However, Marks seems to think that technology is the way forward, which oversimplifies this complex problem. He refers, over nine times in the article, that â€Å"technology† is the way out of poverty. Marks’ contends that, â€Å"The biggest challenge we face isn’t inequality. It’s ignorance. †Ã‚   He makes this statement in spite of having no experience of being black nor poor.Mind you, this is coming from a white guy who was raised in the suburbs and was the former owner of Marks Group PC, a 10 person customer relationship management consulting firm based outside Philadelphia. The point he refers to as â€Å"being poor† are black children that reside in West Philadelphia. He lacks any knowledge regarding these individuals, considering his only understanding of â€Å"West Philadelphia† is not from him his own personal experience but only from a few teachers he knows, which he openly states.It is easy to agree with Marks when he talks about all of the technology enabling things he would do if he were a â€Å"poor black† kid: * Use homework tools like Backpack, and Diigo * Purchased hardware at outlets like Tiger Direct and Dell’s Outlet. * Study sites like SparkNotes and CliffsNote s * Watch relevant teachings on Academic Earth, TED and the Khan Academy. * Get free books from Project Gutenberg * Do research on sites such as, CIA World, Factbook, and Wikipedia These are great ideas for everyone to use whether you are from West Philadelphia or a student at Thomas Nelson.However, these are not cures to grow the middle class. The articles effectiveness is directly calling attention to a national problem, due to the fact that this article was written in Forbes which is intended for wealthy people. The affluent are a key part to any solution for issues of this magnitude. He fails to suggest to his readers any steps they can take to help the situation, but focuses his article on kids who will never pick up a copy of this magazine.What makes this sad is that Gene Marks’ is stating all of these things he would do if he were a poor black kid, yet has failed to actually reach out to these children. For example, Marks’ explains how his kids are just â€Å"l ucky enough to have parents and a well funded school system†¦Ã¢â‚¬  If Marks’ made more of an active attempt to help these children he would be tackling the problem. Marks’ could bridge the span of division by not only talking about the situation but actually doing something about it. Marks’ has an abundance of words, however no action which makes him apart of the great divide.Though this may not be his intent, this article is full of â€Å"between the lines† racial stupidity and arrogance. Marks writes as if poor and black are the same, he states this eight times in the article. Poor does not discriminate among races, bigotry is what discriminates. Unfortunately, Marks under emphasizes the most important elements of success even though he clearly states them, â€Å"It takes brains. It takes hard work. It takes a little luck. † These are well understood methods for success; they are easier said than done.Marks may have good intentions, yet th ey seem underwhelming and overly simplistic to move his audience into appropriate action. Just explaining that there is a problem is not motivating enough to help the situation. Kids don’t just wake up one day, nor do any, and know how to set goals for their futures or what tools are available to help themselves academically. These children need mentors, role models, people who are actively involved in helping them become successful, and not contributors to Forbes who think they are â€Å"rich† lecturing them on a way out of their condition.