Coal tar creosotes products Essays

Coal tar creosotes products Essays Coal tar creosotes products Essay Coal tar creosotes products Essay Coal pitch is among the byproducts when coal is carbonized to do coke or gasified to do coal gas. Coal pitch creosotes are distillation merchandises of coal pitch, while coal pitch pitch is a residue produced during the distillment of coal pitch. Coal pitch pitch volatiles are compounds given off from coal pitch pitch when it is heated. Coal pitch creosotes, coal pitch, coal pitch pitch, and coal pitch pitch volatiles are composed of many single compounds of changing physical and chemical features. In add-on, the composing ofe ach, although referred to by specific name ( e.g. , coal pitch creosote ) is non consistent. For case, the constituents and belongingss of the mixture depend on the temperature of the destructive distillment ( carbonisation ) and on the nature of the carbon-containing stuff used as a feedstock for burning Usually ; coal pitchs are syrupy liquids or semisolids that are black or dark brown with a naphthalene-like olfactory property. Coal pitchs are complex combin ations of polycyclic aromatic hydrocarbons ( PAHs ) , phenols, heterocyclic O, S, and nitrogen compounds. { 1 } Although several hundred chemical compounds have been isolated from coal pitch, a comparatively little figure are present in appreciable sums. These may be grouped as in the tabular array. All the compounds in the tabular array except the monomethylnaphthalenes are of some commercial importance. The byproducts from coal carbonization, particularly coal pitch, have been the chief beginning of chemicals worldwide in the latter half of the nineteenth century. However, during the past four decennaries, crude oil and natural gas have mostly replaced coal as the basic natural stuffs for the production of chemicals. As crude oil and gas militias are worsening quickly, due to their progressively high demand, coal is expected to finally recover its place as a major beginning of chemicals and other non-fuel merchandises in the twenty-first century. Traditionally, Cresylic acids have been obtained from coal pitch. In the United Kingdom, methyl phenols have been conventionally produced from low temperature coal pitchs as a consequence of carbonisation of coal. The chief manufacturer has been Coalite Chemicals. In Germany, Rutgers VFT AG have about perfected coal pitch chemical science and have been bring forthing cresylic acids and 3 5-xylenols for old ages. CdF Chime in France and Nippon Steel chemical co. of Japan has besides been bring forthing some coal tar-based methyl phenols. The most outstanding manufacturer in the field of methyl phenols from coal pitch had been SASOL of South Africa that has been runing coal chemical workss utilizing force per unit area gasification of bitumious coals based on lurgi procedure. In these workss, ab initio phenol and ortho-cresol are separated from the cresylic acid mixture utilizing fractional process, and a mixture rich in methyl phenols ( up to 94 % ) incorporating some xylenols is produced and the merchandise is marketed as assorted methyl phenols ( chiefly para methyl phenol, meta methyl phenol, and little per centum of assorted xylenols and a really small measure of unrecovered phenol ) . Bituminous coal or even lignite pitchs have been used in Germany, Czech Republic, Russia, Ukraine and India for recovery of assorted methyl phenols and xylenols. However, many of these workss, particularly in Germany, are being closed down since coal carbonisation procedures are considered to be harmful to the environment. The Procedure The industry of coke in the byproduct coke ovens normally consequences in the production of 10 to 16 gal of pitch and light oil per ton of coal. ( 1 ) . The petroleum coal pitch is so farther distillated to give 5 % of light oil, 17 % of creosote oil, 17 % of heavy oil and 61 % pitch. Cresols and xylenols recovered from coal pitchs are normally in the signifier of cresylic acid, the cresylic acid is normally approximately 2 to 3 % of the original pitch and it is normally present in the light oil ( up to 200 C ) and the in-between oil ( 200 to 250 ) . The cured cresylic acid typically contains 45 % phenol, 35 % methyl phenols, 15 % xylenols and 5 % other phenolic homologs ( 1 ) Cresols can be obtained by polishing tar acids. These acids consist of the phenolic components present in coal pitch. The byproduct coking of coal outputs an norm of 42 litres of coal pitch. The pitch is distilled ( ! ! ! ) and a fraction known as creosote oil or tar-acid oil is collected. The fraction containing of approximately 17 % is foremost processed to take the naphthalene. The phenols and methyl phenols, nowadays in the pitch to the extent of 0.3 % to 1.1 % , are so removed as follows. The tar-acids, after naphthalene remotion, are charged into a wash armored combat vehicle, where the phenolic organic structures are extracted with Na hydrated oxide solution. Acerb concentrations changing from 8 to 50 % may be utilized, although the higher concentrations are in more general usage. The pitch acids are converted to their several salts, Na phenate and cresylate, which are soluble in the aqueous bed. This bed incorporating the tar-acid salts is allowed to settle in the wash armored combat vehicle and is so discharged from the underside. The nonaqueous ( neutral-oil ) bed is distilled and sent to the pyridine-recovery works ( ! ! ! ) . The Na cresylate from the wash armored combat vehicle is freed of entrained and dissolved oils and the bases by vaporization ( under vacuity ) to controlled concentrations. The concentrated cresylate solution is run from the evaporator into a neutralizer or carbonating armored combat vehicle. Here most of the salts are converted to free pitch acids by intervention with C dioxide. The acids are decanted from the ensuing Na carbonate solution and are so charged into an acidifier. Sulfuric acid, in changing concentrations, is added to finish the procedure of springing the pitch acids. Carbon dioxide intervention can be eliminated by utilizing merely merely sulphuric acid, but this pattern is non common. The released phenols and methyl phenols are separated from aqueous Na sulphate solution in the acidifier by decantation. The top bed, incorporating the phenolic organic structures, is distilled either intermittently or continuously through a fractioning column. Here the H2O is removed an d several fractions such as petroleum phenols methyl phenols and xylenols are taken. The phenol fraction is sent to the phenol-refining works for farther processing. The petroleum methyl phenol cut is farther purified by fractional distillment to give o-cresol and a mixture dwelling of m-and p-cresol. The latter methyl phenols were by and large marketed as a mixture, since their separation is well more hard than the isolation of o-cresol due to the fact that there is a sensible difference in boiling points of o-cresol and other isomers. The two isomers may be refined by the formation of the oxalic-acid add-on merchandise or by the alkylation with an alkene to give compounds that are more readily separated. Hydrolysis and dealkylation, severally, output refined m- and p- methyl phenols. However merely a little fraction of the m-cresol-p-cresol mixture is used to fix the single isomers Until World War 2 about all the cresylic acid was produced from coal pitch by merchandise. The addition in demand during the war led top crude oil refiners to put in installations for recovery the cresylic acid formed in the thermic snap procedures. This was extended to catalytically cracked napthas after the war. These yearss the production of methyl phenols and xylenols are chiefly produced from man-made paths.

Presentation,Practice and Production approach to language teaching Dissertation

Presentation,Practice and Production approach to language teaching between the critiques and the proposed alternative methods - Dissertation Example Cook (2011) maintained that the term foreign language refers to â€Å"a language acquired in a milieu where it is normally in use† (p. 140). Meanwhile, a second language may be defined as â€Å"one that becomes another tool of communication alongside the first language †¦ [and] is typically acquired in a social environment in which it is actually spoken† (Cook, 2011, p. 140). The aforementioned distinction, therefore, is grounded on two dimensions: social and location. The social dimension deals with meeting the communicative need of the learner whereas the location dimension has something to do with the usage of the language in the native locale of the learner (Cook, 2011). Richards and Rodgers (2001) emphasized that current issues in language teaching has been around for centuries and has remained unchanged. Throughout the centuries, the study of foreign languages has shifted importance from one language to the next. In a world where six out of ten individuals sp eak a language which is different from their mother tongue, speaking two or more languages has become the norm rather than an exception. Five hundred years ago, Latin was the prominent language used for education, commerce, religion, and government, particularly in the Western World. During the 16th century, other languages rose to prominence such as French, Italian, and English. These languages eventually supplanted Latin as the language of choice for verbal and written communication (Richards and Rodgers, 2001). Though Latin was relegated as a subject of study in schools, it has become a model for instruction for foreign languages. Instruction was composed of grammar rules, declensions and conjugations, translation, and writing sample sentences. In addition, parallel bilingual texts and dialogues are utilized in teaching. For modern languages, the mode of instruction remained the same in most aspects. Students are provided textbooks on abstract grammar rules, vocabulary lists, and sentences for translation. However, this approach was grounded on the grammatical system of the language, limiting its ability to facilitate genuine communication. This traditional approach to foreign language instruction was referred to as the grammar-translation method (Richards and Rodgers, 2001). In the United States, the grammar-translation method was known as the Prussian method, due to its German scholarly origins. This method has seven characteristics: (1) the goal of foreign language study is grounded on mental discipline and intellectual development; (2) reading and writing is prioritized over speaking or listening; (3) vocabulary instruction is confined to reading bilingual word lists, dictionary study, and memorization; (4) the sentence is the basic unit of teaching and practice; (5) accuracy is prioritized; (6) grammar instruction is deductive in nature; and (7) the speakers native language is utilized as the medium of instruction (Richards and Rodgers, 2001). The gram mar-translation method was widely used for European and foreign language instruction until the 1940s. However, it has been subject to much criticism, mainly on the grounds that its approach to teaching foreign languages mostly involved pointless memorization of vague grammar rules and vocabulary, and translation of stilted or literary prose, much to the frustration of countless students. Mounting opposition to this approach led to the development of new methods of

History vs. Hollywood Cleopatra VII Term Paper Example | Topics and Well Written Essays - 1000 words

History vs. Hollywood Cleopatra VII - Term Paper Example Hence, Hollywood’s version of history is a combination of both fact and fiction. The substance of this prose will focus on Cleopatra, one of the most celebrated personalities both in the ‘real world’ and the silver screen. The latter was portrayed by Elizabeth Taylor in the 1963 adaptation titled â€Å"Cleopatra†. The movie closely follows the actual events but as is expected, there are some aspects that are spiced up, exaggerated or simply omitted due to the lack of appeal. Contrary to eminent historians, Cleopatra’s flawless beauty is the prime theme of the movie that is actually why men were drawn towards her. However, in reality Cleopatra’s beauty was neither jaw-dropping nor capable of driving men insane. In truth, Cleopatra wasn’t the beautiful lass that Elizabeth Taylor depicted her to be; in fact, she was a physically unattractive woman, who used her wit and wisdom as her primary tools of seduction (Grout 2012). The characterization of Caesar was also erroneous as he had never wished to be made emperor or dictator; it had been one of the fears held by the senate that eventually lead to his assassination. Furthermore, the movie also depicted how Caesar and Cleopatra’s affair had become increasingly public and the fact that Cleopatra bore him a son named Caes arion. In the movie, it is shown that Caesar publicly accepts his illegitimate son, Caesarion. Whereas in reality, Caesarion was never acknowledged by Caesar and much to Cleopatra’s ire, Octavian; Caesar’s nephew was proclaimed his heir. Caesar and Cleopatra had never married each other unlike the movie depiction. Historians have stated that Cleopatra’s and Caesar’s relationship was more of a political alliance than a romantic one that suited both individuals; their relationship is greatly dramatized in the movie. Nevertheless, the movie plot still followed the actual events closely and it did incorporate some very interesting details of history. The method through

Investigation of resistivity of nichrome wire Essay Example for Free

Investigation of resistivity of nichrome wire Essay 32 Gauge 28 Gauge Voltage Recorded Percentage Uncertainty % Ammeter The ammeter recorded the current of the circuit with the wire connected to it. 32 Gauge 28 Gauge Current Recorded Percentage Uncertainty %( Current Recorded Percentage Uncertainty. Resistance Thus, as the resistance is calculated using the voltage and current obtained, we have the following resistance percentage uncertainties. 32 Gauge Resistance Uncertainty %( Gauge Resistance Uncertainty % Resistivity This is calculated using the resistance, area and the length. The uncertainties of the resistance and length are used to calculate the uncertainty of the resistivity. The area was not used as it was found by using the gauge value and checked against a referenced site, where diameters were published. As this value was given, the uncertainty was not counted as the method of measurement was not stated. 32 Gauge 28 Gauge Resistivity Uncertainty %(Discussion As the investigation took place, the voltage was increased slowly. This increased the current passing through the circuit. From these values obtained for each of the wires, the resistance and resistivity were calculated. The resistance was calculated from both the values obtained from the experiments and also from the gradient of the graph drawn. This was done so that separate set of resistivities can be obtained and evaluated. As seen from the calculations of the resistance, it is proportional to the length of the wire. The longer the nichrome wire is, the larger the resistance will be. This was certainly the case here as the resistance for the 1 metre wire was more than double that of the 0. 5 metre wire. This larger resistance would be due to the cross-sectional area of the wires. Were the 1 metre wire had a cross-sectional area of 5. 9 x 10-8 m2, the 0. 5 metre was 1. 1 x 10-7 m2, therefore the first nichrome being longer and thinner, causes the resistance to be much larger. The resistivity was calculated for each of the nichrome wires and was found to be very close to one another. The slight difference could be due to experimental errors. The 32gauge wire had a much larger resistance, while being the longer wire and had the thinner cross-sectional area. Taking this all into consideration, the resistivity was calculated at varying voltages and the mean value was 1. 0149 x 10-6 ? m. The gradient from the graph is the resistance, this again was used to calculate a separate value of the resistivity, which was 1. 01496 x 10-6 ? m. This was done as the trend line of the graph was set to the intercept of zero, as when there is no power through the circuit there would be no voltage or current. This value is the same as the value found from the obtained tabulated results. The calculated resistivities for the 28gauge gave similar values. Here the mean value from the obtained current and voltage was 1. 095 x 10-6 ? m, where as the resistivity calculated from the gradient of the graph was 1. 12 x 10-6 ? m. Although these values looking different they are of the standard form of negative 6, meaning they are very small numbers, and therefore this slight difference is minute. Again this resistivity for the 28 gauge in comparison to the resistivity for the 32 gauge is the same, where very small decimal places are slightly out. This investigation led to determining a good value for the resistivity by using two wires of different dimensions. The accepted value for the resistivity of nichrome is 1. 50 i 10-6 ? m. This in ratio to the values obtained is as follows: 32 Gauge 1 This shows that the values obtained are very close to that of the accepted value. To improve the accuracy of the results the experiment should be repeated. In doing so, some variables should be kept constant i. e. the length, gauge or temperature so that an average can be obtained. Bibliography http://www. 8886. co. uk/ref/standard_wire_gauge. htm http://hyperphysics. phy-astr. gsu. edu/hbase/electric/resis. html http://en. wikipedia. org/wiki/Electrical_resistivity Physics Assignment 3 Show preview only The above preview is unformatted text This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

Excellence in Education :: essays research papers

The concept of excellence in education is one that, on the surface, seems to be unquestionable. After all, who would not accede that students within our schools should, in fact, excel? Certainly teachers, parents, and administrators can agree on excellence as an aim to shoot for. The interpretation of the term "excellence" is, however, less obvious. How do we regard excellence? Is it the college bound student with a broad liberal arts education? Is it the student who graduates high school trained in a specific trade? Many in the field of education cannot come to an agreement on how our schools can best achieve excellence for and from our students. One of the many authorities who have contributed a model for what schools should be is Robert L. Ebel. According to Ebel, knowledge is the single most significant and most important goal in the education of children. In his article "What are schools for?" Ebel answers "that schools are for learning, and that what ought to be learned mostly is useful knowledge" (3). He builds this declaration in answer to trends in education that focus upon other aspects of learning in schools. Ebel states in the beginning of his article, that he does not assume schools should be social research agencies, recreational facilities, adjustment centers, or custodial institutions. (3). While he does not deny that our nation is currently wrestling with a dreary array of social ailments, he does argue that the answer to such problems can or should lie within the jurisdiction of our schools. In discussing education’s mission to provide useful knowledge, Ebel defines what he means by the word knowledge: "It is an integrated structure of relationships among concepts and propositions" (5). Knowledge, the way Ebel describes it is not the same as information. Ebel states that "knowledge is built out of information by thinking". Knowledge, according to Ebel, must be constructed from information by each individual learner; it cannot be looked up, or given to students by a parent or teacher. " A student must earn the right to say ‘I know’ by his own thoughtful efforts to understand" (Ebel, 5). The intellectual proficiencies many educators hope to teach are, like information, essentially useless to Ebel without a knowledge base on which to draw from. Ebel feels that a good teacher can "motivate, direct, and assist the learning process to great advantage". Although Ebel feels that good teachers are essential to providing a "favorable learning environment," he puts much of the accountability for learning on the students themselves. Ebel feels that teachers are there to facilitate students in their learning, not to coerce those who are indifferent and unmotivated and do not wish to learn, against their will.

Hope Focused Marriage Counseling Essay

Unlike other explorations insinuated in the context of research, marriage counseling has been one of the unspecialized fields emerged with theoretical assumptions and practice (Stuckert, 2003). This however, has been the challenge to psychologists and practitioners in defying the thought that marriage cannot be taken into research since its hypotheses and results of practice have been acclimated, nevertheless the volume available for study is accumulated. Everett L. Worthington Jr. , a psychology professor and the proponent of over 150 articles tackling issues on marriage, forgiveness and reconciliation was able to find standard procedures on how to keep marriages anchored on Christianity based marital therapy. More specifically, through the light of his year 1999 published book, Hope-Focused Marriage Counseling, couples are to be taken to a self rehabilitation which will give hope to individuals who are living in a room full of skeptic viewpoints about marriage and eventually open a realization that his substantial research shall lead them to a path where â€Å"miracles do happen in the real world. † (Worthington, 1999) Overview Marriage is a shadow of the relationship that we are expected to have with Jesus—permanent, loving, committed. (Eph 5:32) Everett L. Worthington begins his book with a verse in the bible which depicts the meaning of marriage in the most moral and Christian way thus giving a connotation that helping troubled couples is not an easy task. However, she points out the fact that the extent of healing relationships is through developing a character of Christ embodied in every individual’s personality and manifest such with one’s relationships to his or her social network as well (Worthington, 1999). Further, he stresses that when a relationship has Christ as vanguard, life will be inhabited with the verity of love, faith and hope and that then is the start of a bright thing. Strengths What makes his book amazing falls on the grounds of analytic and realistic situations as the core of the gist of the whole scenario. Initially introducing theories then later putting the theories into practice makes readers able to divulge their selves in the dimension that the author intends them to live with. His strategies (advices, so to speak) draws out a hysteria which will make readers know their respective state in life at first, hence, for having been given the momentum to realize what is happening in their lives, they will seek for answers on how to save them from their presumed agony. Further, his approaches through exercises which are efficient to exhibit (Worthington, 1999)—drawing fundamental values, the promotion of confession and forgiveness, communication intensification, aiding conflict resolution, alterations of the pattern of thinking, intimacy development, and the cementing of commitment—gives grandeur to the book as readers can implement these exercises with their partners or core groups. Realistically crafted, he gives marriage counseling a twist by inculcating his own experiences which gives conviction to the statements and recommendations written in his book. One fascinating fact on the book is its distinctiveness in course, since unlike other books on marriage counseling, typically establishing manuals which synonymously suggest divorce or annulment so as not to complicate the situation, this book thinks otherwise. Though the author admitted that is hard and rarely possible in the contemporary society—divorce is legal and other forms of law that allow couples to â€Å"live† without the need of marital rites—still, he fervently believes that the sacred matrimony must be preserved even if others no longer accept as true the tradition and the essence of spiritual intimacy. These ideas represented in the book will coin back the integrity, accountability, prudence and proper teaching among couples. Weaknesses â€Å"Hope-focused rather than problem-focused† (Worthington, 1999) this is the toweringly hopeful campaign of the author. Thus, because of globalization, cultural diversity and the differences of every individual, there may be some who may not appreciate the book for reasons that inhibit the issue on dissimilarity of character, viewpoint in life, tradition and environmental influences. It is evident that the target audiences of the book are Christians—although optimistic individuals would also be interested in reading the book—hence this leads us to a remorseful realization that it will not drive â€Å"naysayer† or a pessimist to read it. Still, fingers are crossed on the intent of the book, and that is to spread the thought that â€Å"change is possible† and in the long run, every couple will be given a new outlook on their marriage for the benefit of their family. Conclusions and further remarks The functions of the husband and the wife bear a multifaceted blueprint of expectations of the responses which are to come from one another. Hence as humans, challenges and trials are inevitable aspects in life and must therefore be taken with full accountability after having vowed under the sacred matrimony and under the blessing of the church. However, in the present era, where several factors influence every person’s character and personality, asking for help and intervention from one who truly understands the quintessence of love and marriage is a an ideal act to do (Stuckert, 2003). Communication mostly is the main problem of couples and Worthington is able to help by producing a masterpiece which, with confidence, he believes will save troubled marriages. Forgive. Reconcile. Change can happen if one will listen while the other speaks. References Stuckert, R. P. (2003). Role Perception and Marital Satisfaction. A Configurational Approach. Marriage and Family Living, 25(4), 415-419. Worthington, E. L. (1999). Hope-Focused Marriage Counseling: A Guide to Brief Therapy. Downers Grove, IL: InterVarsity Press.

Understanding and Processing Keyboard Events in Delphi

Keyboard events, along with mouse events, are the primary elements of a users interaction with your program. Below is information on three events that let you capture a users keystrokes in a Delphi application: OnKeyDown, OnKeyUp and OnKeyPress. Down, Up, Press, Down, Up, Press... Delphi applications can use two methods for receiving the input from the keyboard. If a user has to type something in an application, the easiest way to receive that input is to use one of the controls that automatically responds to keypresses, such as Edit. At other times and for more general purposes, however, we can create procedures in a form that handle three events recognized by forms and by any component that accepts keyboard input. We can write event handlers for these events to respond to any key or key combination the user might press at runtime. Here are those events: OnKeyDown - called when any key on the keyboard is pressedOnKeyUp - called when any key on the keyboard is releasedOnKeyPress - called when a key corresponding to an ASCII character is pressed Keyboard Handlers All the keyboard events have one parameter in common. The Key parameter is the key on the keyboard and is used to pass by reference of the value of the pressed key. The Shift parameter (in the OnKeyDown and OnKeyUp procedures) indicates whether the Shift, Alt, or Ctrl keys are combined with the keystroke. The Sender parameter references the control that was used to call the method. procedure TForm1.FormKeyDown(Sender: TObject; var Key: Word; Shift: TShiftState) ; ... procedure TForm1.FormKeyUp(Sender: TObject; var Key: Word; Shift: TShiftState) ; ... procedure TForm1.FormKeyPress(Sender: TObject; var Key: Char) ; Responding when the user presses shortcut or accelerator keys, such as those provided with menu commands, does not require writing event handlers. What Is Focus? Focus is the ability to receive user input through the mouse or keyboard. Only the object that has the focus can receive a keyboard event. Also, only one component per form can be active, or have the focus, in a running application at any given time. Some components, such as TImage, TPaintBox, TPanel and TLabel cannot receive focus. In general, components derived from TGraphicControl are unable to receive focus. Additionally, components that are invisible at run time (TTimer) cannot receive focus. OnKeyDown, OnKeyUp The OnKeyDown and OnKeyUp events provide the lowest level of keyboard response. Both OnKeyDown and OnKeyUp handlers can respond to all keyboard keys, including function keys and keys combined with the Shift, Alt, and Ctrl keys. The keyboard events are not mutually exclusive. When the user presses a key, both the OnKeyDown and OnKeyPress events are generated, and when the user releases the key, the  OnKeyUp event is generated. When the user presses one of the keys that OnKeyPress does not detect, only the  OnKeyDown event occurs, followed by the  OnKeyUp event. If you hold down a key, the OnKeyUp event occurs after all the OnKeyDown and OnKeyPress events have occurred. OnKeyPress OnKeyPress returns a different ASCII character for g and G, but OnKeyDown and OnKeyUp do not make a distinction between uppercase and lowercase alpha keys. Key and Shift Parameters Since the Key parameter is passed by reference, the event handler can change Key so that the application sees a different key as being involved in the event. This is a way to limit the kinds of characters that the user can input, like to prevent users from typing alpha keys. if Key in [a..z] [A..Z] then Key : #0 The above statement checks whether the Key parameter is in the union of two sets: lowercase characters (i.e. a  through z) and uppercase characters (A-Z). If so, the statement assigns the character value of zero to Key to prevent any input into the Edit component, for example, when it receives the modified key. For non-alphanumeric keys, WinAPI virtual key codes can be used to determine the key pressed. Windows defines special constants for each key the user can press. For example, VK_RIGHT is the virtual key code for the Right Arrow key. To get the key state of some special keys like TAB or PageUp, we can use the GetKeyState Windows API call. The key status specifies whether the key is up, down, or toggled (on or off - alternating each time the key is pressed). if HiWord(GetKeyState(vk_PageUp)) 0 then ShowMessage(PageUp - DOWN) else ShowMessage(PageUp - UP) ; In the OnKeyDown and OnKeyUp events, Key is an unsigned Word value that represents a Windows virtual key. In order to get the character value from Key,  we use the Chr function. In the OnKeyPress event, Key is a Char value that represents an ASCII character. Both OnKeyDown and OnKeyUp events use the Shift parameter, of type TShiftState, a set flags to determine the state of the Alt, Ctrl, and Shift keys when a key is pressed. For example, when you press Ctrl A, the following key events are generated: KeyDown (Ctrl) // ssCtrl KeyDown (CtrlA) //ssCtrl A KeyPress (A) KeyUp (CtrlA) Redirecting Keyboard Events to The Form To trap keystrokes at the form level instead of passing them to the forms components, set the forms KeyPreview property to True (using the Object Inspector). The component still sees the event, but the form has an opportunity to handle it first - to allow or disallow some keys to be pressed, for example. Suppose you have several Edit components on a form and the Form.OnKeyPress procedure looks like: procedure TForm1.FormKeyPress(Sender: TObject; var Key: Char) ; begin if Key in [0..9] then Key : #0 end; If one of the Edit components has the Focus,  and the  KeyPreview property of a form is False, this code will not execute. In other words, if the user presses the 5 key, the 5 character will appear in the focused Edit component. However, if the KeyPreview is set to True, then  the forms OnKeyPress event is executed before the Edit component sees the key that is pressed. Again, if the user has pressed the 5 key, then it assigns the character value of zero to Key to prevent numerical input into the Edit component.