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90-512: Collotype originates from the Greek word kolla for (flour paste) glue. Poitevin patented collotype printing the same year it was invented in 1855. The process was shown in 1859 by F. Joubert. In Poitevin's process, a lithographic stone was coated with a light-sensitive gelatin solution and exposed through a photographic negative. The gelatin would harden in exposed areas, leading to the stone becoming hydrophobic in light areas (and thus receptive to

180-414: A spans many orders of magnitude, a more manageable constant, p K a is more frequently used, where p K a = −log 10 K a . Stronger acids have a smaller p K a than weaker acids. Experimentally determined p K a at 25 °C in aqueous solution are often quoted in textbooks and reference material. Arrhenius acids are named according to their anions . In the classical naming system,

270-425: A tympan before slight pressure is applied. The collotype process uses much less pressure than other types of printing, such as lithography, letterpress or intaglio. While it is possible to print by hand using a roller or brayer, the best consistency in pressure and even distribution of ink is most effectively achieved on a mechanized press. The collotype printing process was used for volume mechanical printing before

360-450: A values are small, but K a1 > K a2 . A triprotic acid (H 3 A) can undergo one, two, or three dissociations and has three dissociation constants, where K a1 > K a2 > K a3 . An inorganic example of a triprotic acid is orthophosphoric acid (H 3 PO 4 ), usually just called phosphoric acid . All three protons can be successively lost to yield H 2 PO 4 , then HPO 4 , and finally PO 4 ,

450-404: A CTP ( computer-to-plate ) device known as a platesetter. The positive image is the emulsion that remains after imaging. Non-image portions of the emulsion have traditionally been removed by a chemical process, though in recent times, plates have become available that do not require such processing. The plate is affixed to a cylinder on a printing press. Dampening rollers apply water, which covers

540-488: A Lewis acid explicitly as such. Modern definitions are concerned with the fundamental chemical reactions common to all acids. Most acids encountered in everyday life are aqueous solutions , or can be dissolved in water, so the Arrhenius and Brønsted–Lowry definitions are the most relevant. The Brønsted–Lowry definition is the most widely used definition; unless otherwise specified, acid–base reactions are assumed to involve

630-447: A Lewis acid, H , but at the same time, they also yield an equal amount of a Lewis base (acetate, citrate, or oxalate, respectively, for the acids mentioned). This article deals mostly with Brønsted acids rather than Lewis acids. Reactions of acids are often generalized in the form HA ⇌ H + A , where HA represents the acid and A is the conjugate base . This reaction is referred to as protolysis . The protonated form (HA) of an acid

720-634: A Lewis base and transfers a lone pair of electrons to form a bond with a hydrogen ion. The species that gains the electron pair is the Lewis acid; for example, the oxygen atom in H 3 O gains a pair of electrons when one of the H—O bonds is broken and the electrons shared in the bond become localized on oxygen. Depending on the context, a Lewis acid may also be described as an oxidizer or an electrophile . Organic Brønsted acids, such as acetic, citric, or oxalic acid, are not Lewis acids. They dissociate in water to produce

810-580: A benzene solvent and in the third gaseous HCl and NH 3 combine to form the solid. A third, only marginally related concept was proposed in 1923 by Gilbert N. Lewis , which includes reactions with acid–base characteristics that do not involve a proton transfer. A Lewis acid is a species that accepts a pair of electrons from another species; in other words, it is an electron pair acceptor. Brønsted acid–base reactions are proton transfer reactions while Lewis acid–base reactions are electron pair transfers. Many Lewis acids are not Brønsted–Lowry acids. Contrast how

900-426: A brushed or roughened texture and are covered with a photosensitive emulsion . A photographic negative of the desired image is placed in contact with the emulsion and the plate is exposed to ultraviolet light . After development, the emulsion shows a reverse of the negative image, which is thus a duplicate of the original (positive) image. The image on the plate emulsion can also be created by direct laser imaging in

990-531: A center, and some of Géricault's prints were in fact produced there. Goya in Bordeaux produced his last series of prints by lithography— The Bulls of Bordeaux of 1828. By the mid-century the initial enthusiasm had somewhat diminished in both countries, although the use of lithography was increasingly favored for commercial applications, which included the prints of Daumier , published in newspapers. Rodolphe Bresdin and Jean-François Millet also continued to practice

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1080-433: A class of strong acids. A common example is toluenesulfonic acid (tosylic acid). Unlike sulfuric acid itself, sulfonic acids can be solids. In fact, polystyrene functionalized into polystyrene sulfonate is a solid strongly acidic plastic that is filterable. Superacids are acids stronger than 100% sulfuric acid. Examples of superacids are fluoroantimonic acid , magic acid and perchloric acid . The strongest known acid

1170-506: A covalent bond with an electron pair. An example is boron trifluoride (BF 3 ), whose boron atom has a vacant orbital that can form a covalent bond by sharing a lone pair of electrons on an atom in a base, for example the nitrogen atom in ammonia (NH 3 ). Lewis considered this as a generalization of the Brønsted definition, so that an acid is a chemical species that accepts electron pairs either directly or by releasing protons (H ) into

1260-406: A flatbed machine, where the plate is made square, level and fixed on the bed. The plate is then dampened with a slightly acidic glycerine –water mixture which is selectively absorbed by the different gel hardnesses, blotted before inking with collotype ink using a leather nap or velvet rollers. Best results are achieved with hard finished paper such as Bristol, placed upon the plate and covered with

1350-406: A flexible plastic or metal plate. The printing plates, made of stone or metal, can be created by a photographic process, a method that may be referred to as "photolithography" (although the term usually refers to a vaguely similar microelectronics manufacturing process ). Offset printing or "offset lithography" is an elaboration of lithography in which the ink is transferred from the plate to

1440-469: A gelatin- albumen mixture to glass , which was then coated with light-sensitized gelatin. This allowed print runs of up to 1,000. This patent was later purchased by Edward Bierstadt , who developed one of the first commercial collotype companies in New York City. The collotype plate is made by coating a plate of glass or metal with a substrate composed of gelatin or other colloid and hardening it. Then it

1530-534: A pH of less than 7. While the Arrhenius concept is useful for describing many reactions, it is also quite limited in its scope. In 1923, chemists Johannes Nicolaus Brønsted and Thomas Martin Lowry independently recognized that acid–base reactions involve the transfer of a proton. A Brønsted–Lowry acid (or simply Brønsted acid) is a species that donates a proton to a Brønsted–Lowry base. Brønsted–Lowry acid–base theory has several advantages over Arrhenius theory. Consider

1620-482: A practical description of an acid. Acids form aqueous solutions with a sour taste, can turn blue litmus red, and react with bases and certain metals (like calcium ) to form salts . The word acid is derived from the Latin acidus , meaning 'sour'. An aqueous solution of an acid has a pH less than 7 and is colloquially also referred to as "acid" (as in "dissolved in acid"), while the strict definition refers only to

1710-415: A printing technology, lithography is different from intaglio printing (gravure), wherein a plate is engraved , etched , or stippled to score cavities to contain the printing ink; and woodblock printing or letterpress printing , wherein ink is applied to the raised surfaces of letters or images. Lithography uses simple chemical processes to create an image. For instance, the positive part of an image

1800-590: A proton to ammonia (NH 3 ), but does not relate to the Arrhenius definition of an acid because the reaction does not produce hydronium. Nevertheless, CH 3 COOH is both an Arrhenius and a Brønsted–Lowry acid. Brønsted–Lowry theory can be used to describe reactions of molecular compounds in nonaqueous solution or the gas phase. Hydrogen chloride (HCl) and ammonia combine under several different conditions to form ammonium chloride , NH 4 Cl. In aqueous solution HCl behaves as hydrochloric acid and exists as hydronium and chloride ions. The following reactions illustrate

1890-521: A rubber blanket , which squeezes away the water, picks up the ink and transfers it to the paper with uniform pressure. The paper passes between the blanket cylinder and a counter-pressure or impression cylinder and the image is transferred to the paper. Because the image is first transferred, or offset to the rubber blanket cylinder, this reproduction method is known as offset lithography or offset printing . Many innovations and technical refinements have been made in printing processes and presses over

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1980-461: A simple solution of an acid compound in water is determined by the dilution of the compound and the compound's K a . Lewis acids have been classified in the ECW model and it has been shown that there is no one order of acid strengths. The relative acceptor strength of Lewis acids toward a series of bases, versus other Lewis acids, can be illustrated by C-B plots . It has been shown that to define

2070-498: A solution with pH 7.0, which is only the case with similar acid and base strengths during a reaction. Neutralization with a base weaker than the acid results in a weakly acidic salt. An example is the weakly acidic ammonium chloride , which is produced from the strong acid hydrogen chloride and the weak base ammonia . Conversely, neutralizing a weak acid with a strong base gives a weakly basic salt (e.g., sodium fluoride from hydrogen fluoride and sodium hydroxide ). In order for

2160-444: A substance that increases the concentration of hydronium ions when added to water. Examples include molecular substances such as hydrogen chloride and acetic acid. An Arrhenius base , on the other hand, is a substance that increases the concentration of hydroxide (OH ) ions when dissolved in water. This decreases the concentration of hydronium because the ions react to form H 2 O molecules: Due to this equilibrium, any increase in

2250-455: A very large number of acidic protons. A diprotic acid (here symbolized by H 2 A) can undergo one or two dissociations depending on the pH. Each dissociation has its own dissociation constant, K a1 and K a2 . The first dissociation constant is typically greater than the second (i.e., K a1 > K a2 ). For example, sulfuric acid (H 2 SO 4 ) can donate one proton to form the bisulfate anion (HSO 4 ), for which K a1

2340-418: Is helium hydride ion , with a proton affinity of 177.8kJ/mol. Superacids can permanently protonate water to give ionic, crystalline hydronium "salts". They can also quantitatively stabilize carbocations . While K a measures the strength of an acid compound, the strength of an aqueous acid solution is measured by pH, which is an indication of the concentration of hydronium in the solution. The pH of

2430-504: Is a dilute aqueous solution of this liquid), sulfuric acid (used in car batteries ), and citric acid (found in citrus fruits). As these examples show, acids (in the colloquial sense) can be solutions or pure substances, and can be derived from acids (in the strict sense) that are solids, liquids, or gases. Strong acids and some concentrated weak acids are corrosive , but there are exceptions such as carboranes and boric acid . The second category of acids are Lewis acids , which form

2520-408: Is a substance that, when added to water, increases the concentration of H ions in the water. Chemists often write H ( aq ) and refer to the hydrogen ion when describing acid–base reactions but the free hydrogen nucleus, a proton , does not exist alone in water, it exists as the hydronium ion (H 3 O ) or other forms (H 5 O 2 , H 9 O 4 ). Thus, an Arrhenius acid can also be described as

2610-488: Is a water-repelling (" hydrophobic ") substance, while the negative image would be water-retaining ("hydrophilic"). Thus, when the plate is introduced to a compatible printing ink and water mixture, the ink will adhere to the positive image and the water will clean the negative image. This allows a flat print plate to be used, enabling much longer and more detailed print runs than the older physical methods of printing (e.g., intaglio printing, letterpress printing). Lithography

2700-514: Is also called an ink pyramid because the ink is transferred through several layers of rollers with different purposes. Fast lithographic 'web' printing presses are commonly used in newspaper production. The advent of desktop publishing made it possible for type and images to be modified easily on personal computers for eventual printing by desktop or commercial presses. The development of digital imagesetters enabled print shops to produce negatives for platemaking directly from digital input, skipping

2790-426: Is also sometimes referred to as the free acid . Acid–base conjugate pairs differ by one proton, and can be interconverted by the addition or removal of a proton ( protonation and deprotonation , respectively). The acid can be the charged species and the conjugate base can be neutral in which case the generalized reaction scheme could be written as HA ⇌ H + A . In solution there exists an equilibrium between

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2880-416: Is coated with a thick coat of dichromated gelatin and dried carefully at a controlled temperature (a little over 50° Celsius ) so it "reticulates" or breaks up into a finely grained pattern when washed later in approximately 16 °C water. The plate is then exposed in contact with the negative using an ultraviolet (UV) source which changes the ability of the exposed gelatin to absorb water later. The plate

2970-516: Is developed by carefully washing out the dichromate salt and dried without heat. The plate is left in a cool dry place to cure for 24 hours before using it to print. Related processes, or processes developed from collotype, or even alternate names for collotype include albertype, alethetype, autocopyist, artotype, gelatinotypy, heliotype, hydrotype, indotint, ink-photo, leimtype, lichtdruck, papryrotype, photogelatin, photophane, phototype, Roto-Collotype, Rye's, and Sinop. In 1874, Joseph Albert produced

3060-472: Is simply added to the name of the ionic compound. Thus, for hydrogen chloride, as an acid solution, the IUPAC name is aqueous hydrogen chloride. The strength of an acid refers to its ability or tendency to lose a proton. A strong acid is one that completely dissociates in water; in other words, one mole of a strong acid HA dissolves in water yielding one mole of H and one mole of the conjugate base, A , and none of

3150-415: Is still used on older presses, using rollers covered with molleton (cloth) that absorbs the water. This increased control of the water flow to the plate and allowed for better ink and water balance. Recent dampening systems include a "delta effect or vario", which slows the roller in contact with the plate, thus creating a sweeping movement over the ink image to clean impurities known as "hickies". This press

3240-422: Is very large; then it can donate a second proton to form the sulfate anion (SO 4 ), wherein the K a2 is intermediate strength. The large K a1 for the first dissociation makes sulfuric a strong acid. In a similar manner, the weak unstable carbonic acid (H 2 CO 3 ) can lose one proton to form bicarbonate anion (HCO 3 ) and lose a second to form carbonate anion (CO 3 ). Both K

3330-425: The citrate ion. Although the subsequent loss of each hydrogen ion is less favorable, all of the conjugate bases are present in solution. The fractional concentration, α (alpha), for each species can be calculated. For example, a generic diprotic acid will generate 3 species in solution: H 2 A, HA , and A . The fractional concentrations can be calculated as below when given either the pH (which can be converted to

3420-400: The solute . A lower pH means a higher acidity , and thus a higher concentration of positive hydrogen ions in the solution. Chemicals or substances having the property of an acid are said to be acidic . Common aqueous acids include hydrochloric acid (a solution of hydrogen chloride that is found in gastric acid in the stomach and activates digestive enzymes ), acetic acid (vinegar

3510-563: The United States, and as of 1997, there were no commercial collotype printers in the United States. As of 2015, there were two commercial collotype printers in Kyoto, Japan. In Europe, the firm Fratelli Alinari ( Florence ) and Lichtdruck-Kunst ( Leipzig ) still produce collotypes, primarily as high-quality art reproductions for museums. In 2010, only a small number of facilities in the United States, primarily art studios or organizations, still have

3600-406: The [H ]) or the concentrations of the acid with all its conjugate bases: A plot of these fractional concentrations against pH, for given K 1 and K 2 , is known as a Bjerrum plot . A pattern is observed in the above equations and can be expanded to the general n -protic acid that has been deprotonated i -times: where K 0 = 1 and the other K-terms are the dissociation constants for

3690-402: The ability to create collotypes. Lithography Lithography (from Ancient Greek λίθος ( líthos )  'stone' and γράφω ( gráphō )  'to write') is a planographic method of printing originally based on the immiscibility of oil and water. The printing is from a stone ( lithographic limestone ) or a metal plate with a smooth surface. It

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3780-424: The acid and its conjugate base. The equilibrium constant K is an expression of the equilibrium concentrations of the molecules or the ions in solution. Brackets indicate concentration, such that [H 2 O] means the concentration of H 2 O . The acid dissociation constant K a is generally used in the context of acid–base reactions. The numerical value of K a is equal to the product (multiplication) of

3870-435: The acid. Neutralization is the reaction between an acid and a base, producing a salt and neutralized base; for example, hydrochloric acid and sodium hydroxide form sodium chloride and water: Neutralization is the basis of titration , where a pH indicator shows equivalence point when the equivalent number of moles of a base have been added to an acid. It is often wrongly assumed that neutralization should result in

3960-416: The artist. The serilith technique is used primarily to create fine art limited print editions. Acidic An acid is a molecule or ion capable of either donating a proton (i.e. hydrogen ion, H ), known as a Brønsted–Lowry acid , or forming a covalent bond with an electron pair , known as a Lewis acid . The first category of acids are the proton donors, or Brønsted–Lowry acids . In

4050-513: The artists' work. Grant Wood , George Bellows , Alphonse Mucha , Max Kahn , Pablo Picasso , Eleanor Coen , Jasper Johns , David Hockney , Susan Dorothea White , and Robert Rauschenberg are a few of the artists who have produced most of their prints in the medium. M. C. Escher is considered a master of lithography, and many of his prints were created using this process. More than other printmaking techniques, printmakers in lithography still largely depend on access to good printers , and

4140-402: The blank portions of the plate but is repelled by the emulsion of the image area. Hydrophobic ink, which is repelled by the water and only adheres to the emulsion of the image area, is then applied by the inking rollers. If this image were transferred directly to paper, it would create a mirror-type image and the paper would become too wet. Instead, the plate rolls against a cylinder covered with

4230-438: The concentration of hydronium is accompanied by a decrease in the concentration of hydroxide. Thus, an Arrhenius acid could also be said to be one that decreases hydroxide concentration, while an Arrhenius base increases it. In an acidic solution, the concentration of hydronium ions is greater than 10 moles per liter. Since pH is defined as the negative logarithm of the concentration of hydronium ions, acidic solutions thus have

4320-423: The concentrations of the products divided by the concentration of the reactants, where the reactant is the acid (HA) and the products are the conjugate base and H . The stronger of two acids will have a higher K a than the weaker acid; the ratio of hydrogen ions to acid will be higher for the stronger acid as the stronger acid has a greater tendency to lose its proton. Because the range of possible values for K

4410-412: The delicacy of the process. As collotype is a hand-printed process, it can be printed on hand-made paper , which differentiates it from other forms of photographic reproduction. The collotype printing process did not achieve commercial viability until Joseph Albert invented the first mechanized collotype press in 1868. Short runs can printed on a proofing press, but longer print runs are carried out on

4500-599: The development of the medium has been greatly influenced by when and where these have been established. An American scene for lithography was founded by Robert Blackburn in New York City. As a special form of lithography, the serilith or seriolithograph process is sometimes used. Seriliths are mixed-media original prints created in a process in which an artist uses the lithograph and serigraph (screen printing). Fine art prints of this type are published by artists and publishers worldwide, and are widely accepted and collected. The separations for both processes are hand-drawn by

4590-487: The durability of the image on the stone depends on the lipid content of the material being used, and its ability to withstand water and acid. After the drawing of the image, an aqueous solution of gum arabic , weakly acidified with nitric acid ( HNO 3 ) is applied to the stone. The function of this solution is to create a hydrophilic layer of calcium nitrate salt, Ca(NO 3 ) 2 , and gum arabic on all non-image surfaces. The gum solution penetrates into

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4680-402: The edges of the print appear as diffuse fine curved lines, unlike the more defined edges of relief or intaglio prints. Richard Benson has described the finnicky nature of collotype printing, primarily problems of registration with damp paper and the varied tones from sheet to sheet. As a young printer during the 1960s, Benson recalled how superstitious the collotype printers were because of

4770-453: The first color collotypes with three collotype plates, each inked in a different color. In 1882, the Hoeschtype, which used six plates, was patented. Mezzograph was a trade name used by Valentine Co. Ltd. of Scotland, for their multicolored postcards, printed in a hybrid process where colors were printed via photolithography and then overprinted in black or blue collotype for the "outlines" of

4860-413: The fluoride nucleus than they are in the lone fluoride ion. BF 3 is a Lewis acid because it accepts the electron pair from fluoride. This reaction cannot be described in terms of Brønsted theory because there is no proton transfer. The second reaction can be described using either theory. A proton is transferred from an unspecified Brønsted acid to ammonia, a Brønsted base; alternatively, ammonia acts as

4950-449: The following reactions are described in terms of acid–base chemistry: In the first reaction a fluoride ion , F , gives up an electron pair to boron trifluoride to form the product tetrafluoroborate . Fluoride "loses" a pair of valence electrons because the electrons shared in the B—F bond are located in the region of space between the two atomic nuclei and are therefore more distant from

5040-427: The following reactions of acetic acid (CH 3 COOH), the organic acid that gives vinegar its characteristic taste: Both theories easily describe the first reaction: CH 3 COOH acts as an Arrhenius acid because it acts as a source of H 3 O when dissolved in water, and it acts as a Brønsted acid by donating a proton to water. In the second example CH 3 COOH undergoes the same transformation, in this case donating

5130-437: The greasy ink) and hydrophilic under dark areas (ink-repelling). The stone was then printed via the standard lithographic process, producing a monochrome print. In 1865, Tessie du Motay and C. R. Marechal applied the gelatin to a copper plate, which was easier to handle than a lithographic stone. However, the gelatin did not adhere well and limited print runs to about 100. In 1868, Joseph Albert and Jakub Husník applied

5220-410: The gum arabic surfaces and was repelled by the oily parts, while the oily ink used for printing did the opposite. Lithography works because of the mutual repulsion of oil and water . The image is drawn on the surface of the print plate with a fat or oil-based medium (hydrophobic) such as a wax crayon , which may be pigmented to make the drawing visible. A wide range of oil-based media is available, but

5310-420: The gum-treated parts, making them even more oil-repellant. An oil-based ink was then applied, and would stick only to the original drawing. The ink would finally be transferred to a blank sheet of paper , producing a printed page. This traditional technique is still used for fine art printmaking. In modern commercial lithography, the image is transferred or created as a patterned polymer coating applied to

5400-414: The image to be printed was drawn with a greasy substance, such as oil, fat, or wax onto the surface of a smooth and flat limestone plate. The stone was then treated with a mixture of weak acid and gum arabic ("etch") that made the parts of the stone's surface that were not protected by the grease more hydrophilic (water attracting). For printing, the stone was first moistened. The water adhered only to

5490-739: The image. Halftone collotype processes combine halftone printing and collotype. These include the Jaffetype, developed in Vienna; the Aquatone, developed and patented by Robert John in the United States in 1922, in which the gelatin is not reticulated; the Gelatone process, introduced in 1939; and the Optak process, introduced in 1946. Collotype was most often printed in monochrome in various colors of ink, most commonly black, brown, green, blue. In double-rolled collotype,

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5580-449: The intermediate step of photographing an actual page layout. The development of the digital platesetter during the late 20th century eliminated film negatives altogether by exposing printing plates directly from digital input, a process known as computer-to-plate printing. During the early years of the 19th century, lithography had only a limited effect on printmaking , mainly because technical difficulties remained to be overcome. Germany

5670-538: The introduction of simpler and cheaper offset lithography . It can produce results difficult to distinguish from metal-based photographic prints because of its microscopically fine reticulations which compose the image. Many old postcards are collotypes. Its possibilities for fine art photography were first employed in the United States by Alfred Stieglitz and Tong Jixu 's Yanguangshi Publishing House in China in post WWI period. Because of its ability to print fine detail, it

5760-450: The ionic suffix is dropped and replaced with a new suffix, according to the table following. The prefix "hydro-" is used when the acid is made up of just hydrogen and one other element. For example, HCl has chloride as its anion, so the hydro- prefix is used, and the -ide suffix makes the name take the form hydrochloric acid . Classical naming system: In the IUPAC naming system, "aqueous"

5850-464: The limitations of Arrhenius's definition: As with the acetic acid reactions, both definitions work for the first example, where water is the solvent and hydronium ion is formed by the HCl solute. The next two reactions do not involve the formation of ions but are still proton-transfer reactions. In the second reaction hydrogen chloride and ammonia (dissolved in benzene ) react to form solid ammonium chloride in

5940-537: The medium in France, and Adolph Menzel in Germany. In 1862 the publisher Cadart tried to initiate a portfolio of lithographs by various artists, which was not successful but included several prints by Manet . The revival began during the 1870s, especially in France with artists such as Odilon Redon , Henri Fantin-Latour and Degas producing much of their work in this manner. The need for strictly limited editions to maintain

6030-503: The more easily it loses a proton, H . Two key factors that contribute to the ease of deprotonation are the polarity of the H—A bond and the size of atom A, which determines the strength of the H—A bond. Acid strengths are also often discussed in terms of the stability of the conjugate base. Stronger acids have a larger acid dissociation constant , K a and a lower p K a than weaker acids. Sulfonic acids , which are organic oxyacids, are

6120-600: The order of Lewis acid strength at least two properties must be considered. For Pearson's qualitative HSAB theory the two properties are hardness and strength while for Drago's quantitative ECW model the two properties are electrostatic and covalent. Monoprotic acids, also known as monobasic acids, are those acids that are able to donate one proton per molecule during the process of dissociation (sometimes called ionization) as shown below (symbolized by HA): Common examples of monoprotic acids in mineral acids include hydrochloric acid (HCl) and nitric acid (HNO 3 ). On

6210-423: The orthophosphate ion, usually just called phosphate . Even though the positions of the three protons on the original phosphoric acid molecule are equivalent, the successive K a values differ since it is energetically less favorable to lose a proton if the conjugate base is more negatively charged. An organic example of a triprotic acid is citric acid , which can successively lose three protons to finally form

6300-740: The other hand, for organic acids the term mainly indicates the presence of one carboxylic acid group and sometimes these acids are known as monocarboxylic acid. Examples in organic acids include formic acid (HCOOH), acetic acid (CH 3 COOH) and benzoic acid (C 6 H 5 COOH). Polyprotic acids, also known as polybasic acids, are able to donate more than one proton per acid molecule, in contrast to monoprotic acids that only donate one proton per molecule. Specific types of polyprotic acids have more specific names, such as diprotic (or dibasic) acid (two potential protons to donate), and triprotic (or tribasic) acid (three potential protons to donate). Some macromolecules such as proteins and nucleic acids can have

6390-431: The paper indirectly by means of a rubber plate or cylinder, rather than by direct contact. This technique keeps the paper dry and allows fully automated high-speed operation. It has mostly replaced traditional lithography for medium- and high-volume printing: since the 1960s, most books and magazines, especially when illustrated in colour, are printed with offset lithography from photographically created metal plates. As

6480-415: The plate was first inked with stiff black ink and then re-inked with a softer colored ink; only one impression was taken. This process was most common in fancy postcards. Collotype has a finely reticulated pattern that captures the tonal shifts of photography with a much more subtle effect that other photographic printing processes of the late 19th century, such as halftone engraving. Under magnification ,

6570-410: The pores of the stone, completely surrounding the original image with a hydrophilic layer that will not accept the printing ink. Using lithographic turpentine , the printer then removes any excess of the greasy drawing material, but a hydrophobic molecular film of it remains tightly bonded to the surface of the stone, rejecting the gum arabic and water, but ready to accept the oily ink. When printing,

6660-417: The price had now been realized, and the medium became more accepted. In the 1890s, color lithography gained success in part by the emergence of Jules Chéret , known as the father of the modern poster , whose work went on to inspire a new generation of poster designers and painters, most notably Toulouse-Lautrec , and former student of Chéret, Georges de Feure . By 1900 the medium in both color and monotone

6750-496: The printing of wallpaper; but it was transformed when the founder's grandson, Fernand Mourlot , invited a number of 20th-century artists to explore the complexities of fine art printing. Mourlot encouraged the painters to work directly on lithographic stones in order to create original artworks that could then be executed under the direction of master printers in small editions. The combination of modern artist and master printer resulted in lithographs that were used as posters to promote

6840-423: The protonated acid HA. In contrast, a weak acid only partially dissociates and at equilibrium both the acid and the conjugate base are in solution. Examples of strong acids are hydrochloric acid (HCl), hydroiodic acid (HI), hydrobromic acid (HBr), perchloric acid (HClO 4 ), nitric acid (HNO 3 ) and sulfuric acid (H 2 SO 4 ). In water each of these essentially ionizes 100%. The stronger an acid is,

6930-406: The solution, which then accept electron pairs. Hydrogen chloride, acetic acid, and most other Brønsted–Lowry acids cannot form a covalent bond with an electron pair, however, and are therefore not Lewis acids. Conversely, many Lewis acids are not Arrhenius or Brønsted–Lowry acids. In modern terminology, an acid is implicitly a Brønsted acid and not a Lewis acid, since chemists almost always refer to

7020-434: The special case of aqueous solutions , proton donors form the hydronium ion H 3 O and are known as Arrhenius acids . Brønsted and Lowry generalized the Arrhenius theory to include non-aqueous solvents . A Brønsted or Arrhenius acid usually contains a hydrogen atom bonded to a chemical structure that is still energetically favorable after loss of H . Aqueous Arrhenius acids have characteristic properties that provide

7110-495: The stone and paper are run through a press that applies even pressure over the surface, transferring the ink to the paper and off the stone. Senefelder had experimented during the early 19th century with multicolor lithography; in his 1819 book, he predicted that the process would eventually be perfected and used to reproduce paintings. Multi-color printing was introduced by a new process developed by Godefroy Engelmann (France) in 1837 known as chromolithography . A separate stone

7200-404: The stone is kept wet with water. The water is naturally attracted to the layer of gum and salt created by the acid wash. Printing ink based on drying oils such as linseed oil and varnish loaded with pigment is then rolled over the surface. The water repels the greasy ink but the hydrophobic areas left by the original drawing material accept it. When the hydrophobic image is loaded with ink,

7290-439: The transfer of a proton (H ) from an acid to a base. Hydronium ions are acids according to all three definitions. Although alcohols and amines can be Brønsted–Lowry acids, they can also function as Lewis bases due to the lone pairs of electrons on their oxygen and nitrogen atoms. In 1884, Svante Arrhenius attributed the properties of acidity to hydrogen ions (H ), later described as protons or hydrons . An Arrhenius acid

7380-409: The years, including the development of presses with multiple units (each containing one printing plate) that can print multi-color images in one pass on both sides of the sheet, and presses that accommodate continuous rolls ( webs ) of paper, known as web presses. Another innovation was the continuous dampening system first introduced by Dahlgren, instead of the old method (conventional dampening) which

7470-737: Was a quick, cheap process and had been used to print British army maps during the Peninsular War . Most of the commercial maps of the second half of the 19th century were lithographed and unattractive, though accurate enough." High-volume lithography is used to produce posters, maps, books, newspapers, and packaging—just about any smooth, mass-produced item with print and graphics on it. Most books, indeed all types of high-volume text, are printed using offset lithography. For offset lithography, which depends on photographic processes, flexible aluminum , polyester , mylar or paper printing plates are used instead of stone tablets. Modern printing plates have

7560-438: Was also used for business cards and invitations with fine script lettering. Eadward Muybridge's Animal Locomotion: an Electro-Photographic Investigation of Connective Phases of Animal Movements (1883–86, printed 1887) was printed in collotype from photographs transferred to gelatin. After collotype had fallen out of commercial use, artists began to experiment with the process. Pablo Picasso's 1920 artist's book Le Tricorne

7650-515: Was an accepted part of printmaking. During the 20th century, a group of artists, including Braque , Calder , Chagall , Dufy , Léger , Matisse , Miró , and Picasso , rediscovered the largely undeveloped artform of lithography thanks to the Mourlot Studios , also known as Atelier Mourlot , a Parisian printshop founded in 1852 by the Mourlot family. The Atelier Mourlot originally specialized in

7740-520: Was invented by Alois Senefelder in the Kingdom of Bavaria in 1796. In the early days of lithography, a smooth piece of limestone was used (hence the name "lithography": "lithos" ( λιθος ) is the Ancient Greek word for "stone"). After the oil-based image was put on the surface, a solution of gum arabic in water was applied, the gum sticking only to the non-oily surface. During printing, water adhered to

7830-493: Was invented in 1796 by the German author and actor Alois Senefelder and was initially used mostly for musical scores and maps. Lithography can be used to print text or images onto paper or other suitable material. A lithograph is something printed by lithography, but this term is only used for fine art prints and some other, mostly older, types of printed matter, not for those made by modern commercial lithography. Originally,

7920-478: Was printed in (black) collotype with applied pochoir color. Surrealist Max Ernst printed the frottages in the portfolio Natural History (1926) in collotype. Marcel Duchamp's La Boîte-en-valise ( Box in a Suitcase ), produced in the 1930s and 1940s, combines the techniques of collotype and stencil to create its "copies." Gerhard Richter's Mao (1968) is a collotype portrait of Mao Zedong . As of 1983, there were only two commercial collotype firms in

8010-666: Was the main center of production in this period. Godefroy Engelmann , who moved his press from Mulhouse to Paris in 1816, largely succeeded in resolving the technical problems, and during the 1820s lithography was adopted by artists such as Delacroix and Géricault . After early experiments such as Specimens of Polyautography (1803), which had experimental works by a number of British artists including Benjamin West , Henry Fuseli , James Barry , Thomas Barker of Bath , Thomas Stothard , Henry Richard Greville , Richard Cooper , Henry Singleton , and William Henry Pyne , London also became

8100-444: Was used for each color, and a print went through the press separately for each stone. The main challenge was to keep the images aligned ( in register ). This method lent itself to images consisting of large areas of flat color, and resulted in the characteristic poster designs of this period. "Lithography, or printing from soft stone, largely took the place of engraving in the production of English commercial maps after about 1852. It

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