Misplaced Pages

#316683

82-446: Rubric can also mean the red ink or paint used to make rubrics, or the pigment used to make it. Although red was most often used, other colours came into use from the late Middle Ages onwards, and the word rubric was used for these also. Medievalists can use patterns of rubrication to help identify textual traditions. Various figurative senses of the word have been extended from its original meaning. Usually these senses are used within

164-461: A cave at Twin Rivers, near Lusaka , Zambia . Ochre , iron oxide, was the first color of paint. A favored blue pigment was derived from lapis lazuli . Pigments based on minerals and clays often bear the name of the city or region where they were originally mined. Raw sienna and burnt sienna came from Siena , Italy , while raw umber and burnt umber came from Umbria . These pigments were among

246-518: A mercury sulfide , was originally made by grinding a powder of natural cinnabar . From the 17th century on, it was also synthesized from the elements. It was favored by old masters such as Titian . Indian yellow was once produced by collecting the urine of cattle that had been fed only mango leaves. Dutch and Flemish painters of the 17th and 18th centuries favored it for its luminescent qualities, and often used it to represent sunlight . Since mango leaves are nutritionally inadequate for cattle,

328-501: A solution with another substance, the solvent . Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubility of a substance in a specific solvent is generally measured as the concentration of the solute in a saturated solution, one in which no more solute can be dissolved. At this point, the two substances are said to be at the solubility equilibrium . For some solutes and solvents, there may be no such limit, in which case

410-564: A black pigment since prehistoric times. The first known synthetic pigment was Egyptian blue , which is first attested on an alabaster bowl in Egypt dated to Naqada III ( circa 3250 BC). Egyptian blue (blue frit), calcium copper silicate CaCuSi 4 O 10 , made by heating a mixture of quartz sand, lime , a flux and a copper source, such as malachite . Already invented in the Predynastic Period of Egypt , its use became widespread by

492-410: A computer display. The appearance of a pigment may depend on the brand and even the batch. Furthermore, pigments have inherently complex reflectance spectra that will render their color appearance greatly different depending on the spectrum of the source illumination , a property called metamerism . Averaged measurements of pigment samples will only yield approximations of their true appearance under

574-421: A given compound may increase or decrease with temperature. The van 't Hoff equation relates the change of solubility equilibrium constant ( K sp ) to temperature change and to reaction enthalpy change. For most solids and liquids, their solubility increases with temperature because their dissolution reaction is endothermic (Δ H  > 0). In liquid water at high temperatures, (e.g. that approaching

656-447: A large increase in solubility with temperature (Δ H  > 0). Some solutes (e.g. sodium chloride in water) exhibit solubility that is fairly independent of temperature (Δ H  ≈ 0). A few, such as calcium sulfate ( gypsum ) and cerium(III) sulfate , become less soluble in water as temperature increases (Δ H  < 0). This is also the case for calcium hydroxide ( portlandite ), whose solubility at 70 °C

738-422: A lesser extent, solubility will depend on the ionic strength of solutions. The last two effects can be quantified using the equation for solubility equilibrium . For a solid that dissolves in a redox reaction, solubility is expected to depend on the potential (within the range of potentials under which the solid remains the thermodynamically stable phase). For example, solubility of gold in high-temperature water

820-501: A long time to establish (hours, days, months, or many years; depending on the nature of the solute and other factors). The rate of dissolution can be often expressed by the Noyes–Whitney equation or the Nernst and Brunner equation of the form: where: For dissolution limited by diffusion (or mass transfer if mixing is present), C s {\displaystyle C_{s}}

902-411: A minimum, which is below 120 °C for most permanent gases ), but more soluble in organic solvents (endothermic dissolution reaction related to their solvation). The chart shows solubility curves for some typical solid inorganic salts in liquid water (temperature is in degrees Celsius , i.e. kelvins minus 273.15). Many salts behave like barium nitrate and disodium hydrogen arsenate , and show

SECTION 10

#1732845226317

984-517: A more complex pattern is observed, as with sodium sulfate , where the less soluble deca hydrate crystal ( mirabilite ) loses water of crystallization at 32 °C to form a more soluble anhydrous phase ( thenardite ) with a smaller change in Gibbs free energy (Δ G ) in the dissolution reaction. The solubility of organic compounds nearly always increases with temperature. The technique of recrystallization , used for purification of solids, depends on

1066-426: A percentage in this case, and the abbreviation "w/w" may be used to indicate "weight per weight". (The values in g/L and g/kg are similar for water, but that may not be the case for other solvents.) Alternatively, the solubility of a solute can be expressed in moles instead of mass. For example, if the quantity of solvent is given in kilograms , the value is the molality of the solution (mol/kg). The solubility of

1148-406: A percentage, and the abbreviation "v/v" for "volume per volume" may be used to indicate this choice. Conversion between these various ways of measuring solubility may not be trivial, since it may require knowing the density of the solution — which is often not measured, and cannot be predicted. While the total mass is conserved by dissolution, the final volume may be different from both the volume of

1230-514: A priest explaining what he must do during a liturgy were also rubricated in missals and the other liturgical books, and the texts to be spoken aloud were in black. From this, "rubric" has a secondary denotation of an instruction in a text, regardless of how it is actually inscribed. This is the oldest recorded definition in English, found in 1375. Less formally, "rubrics" may refer to any liturgical action customarily performed, whether or not pursuant to

1312-471: A simple ionic compound (with positive and negative ions) such as sodium chloride (common salt) is easily soluble in a highly polar solvent (with some separation of positive (δ+) and negative (δ-) charges in the covalent molecule) such as water , as thus the sea is salty as it accumulates dissolved salts since early geological ages. The solubility is favored by entropy of mixing (Δ S ) and depends on enthalpy of dissolution (Δ H ) and

1394-821: A single grade or mark. Rubrics, therefore, help teachers grade more objectively and "they improve students' ability to include required elements of an assignment". Pigment A pigment is a powder used to add color or change visual appearance. Pigments are completely or nearly insoluble and chemically unreactive in water or another medium; in contrast, dyes are colored substances which are soluble or go into solution at some stage in their use. Dyes are often organic compounds whereas pigments are often inorganic . Pigments of prehistoric and historic value include ochre , charcoal , and lapis lazuli . In 2006, around 7.4 million tons of inorganic , organic , and special pigments were marketed worldwide. According to an April 2018 report by Bloomberg Businessweek ,

1476-409: A slightly more greenish or reddish blue. The following are some of the attributes of pigments that determine their suitability for particular manufacturing processes and applications: Swatches are used to communicate colors accurately. The types of swatches are dictated by the media, i.e., printing, computers, plastics, and textiles. Generally, the medium that offers the broadest gamut of color shades

1558-463: A solute's different solubilities in hot and cold solvent. A few exceptions exist, such as certain cyclodextrins . For condensed phases (solids and liquids), the pressure dependence of solubility is typically weak and usually neglected in practice. Assuming an ideal solution , the dependence can be quantified as: where the index i {\displaystyle i} iterates the components, N i {\displaystyle N_{i}}

1640-449: A solvent depends primarily on its polarity . For example, a very polar ( hydrophilic ) solute such as urea is very soluble in highly polar water, less soluble in fairly polar methanol , and practically insoluble in non-polar solvents such as benzene . In contrast, a non-polar or lipophilic solute such as naphthalene is insoluble in water, fairly soluble in methanol, and highly soluble in non-polar benzene. In even more simple terms

1722-403: A specific source of illumination. Computer display systems use a technique called chromatic adaptation transforms to emulate the correlated color temperature of illumination sources, and cannot perfectly reproduce the intricate spectral combinations originally seen. In many cases, the perceived color of a pigment falls outside of the gamut of computer displays and a method called gamut mapping

SECTION 20

#1732845226317

1804-427: A substance in a liquid may also be expressed as the quantity of solute per quantity of solution , rather than of solvent. For example, following the common practice in titration , it may be expressed as moles of solute per litre of solution (mol/L), the molarity of the latter. In more specialized contexts the solubility may be given by the mole fraction (moles of solute per total moles of solute plus solvent) or by

1886-433: A synthetic form of lapis lazuli . Ultramarine was manufactured by treating aluminium silicate with sulfur . Various forms of cobalt blue and Cerulean blue were also introduced. In the early 20th century, Phthalo Blue , a synthetic metallo-organic pigment was prepared. At the same time, Royal Blue , another name once given to tints produced from lapis lazuli, has evolved to signify a much lighter and brighter color, and

1968-510: A trademark. Colour Index International resolves all these conflicting historic, generic, and proprietary names so that manufacturers and consumers can identify the pigment (or dye) used in a particular color product. In the CII, all phthalocyanine blue pigments are designated by a generic color index number as either PB15 or PB16, short for pigment blue 15 and pigment blue 16; these two numbers reflect slight variations in molecular structure, which produce

2050-452: A written instruction. The history, status, and authority of the content of rubrics are significant, and sometimes controversial, among liturgical scholars. In the past, some theologians distinguished between rubrics they considered of Divine origin and those merely of human origin. Rubrics were probably originally verbal, and then written in separate volumes. The earliest extant liturgical books do not contain them, but from references in texts of

2132-432: Is about half of its value at 25 °C. The dissolution of calcium hydroxide in water is also an exothermic process (Δ H  < 0). As dictated by the van 't Hoff equation and Le Chatelier's principle , lowe temperatures favorsf dissolution of Ca(OH) 2 . Portlandite solubility increases at low temperature. This temperature dependence is sometimes referred to as "retrograde" or "inverse" solubility. Occasionally,

2214-566: Is also often used to distinguish words spoken by the celebrant and those by the congregation, or by other specific persons involved in the liturgy, e.g. those marrying. With the arrival of printing , other typographic effects such as italic type , bolded type, or different sizes of type were used to emphasize a section of text, and as printing in two colours is more expensive and time consuming, rubrication has tended to be reserved for sacred and liturgical books or luxury editions of other works. William Morris 's medievally inspired typography for

2296-399: Is defined for specific phases . For example, the solubility of aragonite and calcite in water are expected to differ, even though they are both polymorphs of calcium carbonate and have the same chemical formula . The solubility of one substance in another is determined by the balance of intermolecular forces between the solvent and solute, and the entropy change that accompanies

2378-407: Is difficult to replicate on a computer display . Approximations are required. The Munsell Color System provides an objective measure of color in three dimensions: hue, value (or lightness), and chroma. Computer displays in general fail to show the true chroma of many pigments, but the hue and lightness can be reproduced with relative accuracy. However, when the gamma of a computer display deviates from

2460-656: Is equal to the solubility of the substance. When the dissolution rate of a pure substance is normalized to the surface area of the solid (which usually changes with time during the dissolution process), then it is expressed in kg/m s and referred to as "intrinsic dissolution rate". The intrinsic dissolution rate is defined by the United States Pharmacopeia . Dissolution rates vary by orders of magnitude between different systems. Typically, very low dissolution rates parallel low solubilities, and substances with high solubilities exhibit high dissolution rates, as suggested by

2542-433: Is less than 0.1 g per 100 mL of solvent. Solubility occurs under dynamic equilibrium, which means that solubility results from the simultaneous and opposing processes of dissolution and phase joining (e.g. precipitation of solids ). A stable state of the solubility equilibrium occurs when the rates of dissolution and re-joining are equal, meaning the relative amounts of dissolved and non-dissolved materials are equal. If

Rubric - Misplaced Pages Continue

2624-497: Is not an instantaneous process. The rate of solubilization (in kg/s) is related to the solubility product and the surface area of the material. The speed at which a solid dissolves may depend on its crystallinity or lack thereof in the case of amorphous solids and the surface area (crystallite size) and the presence of polymorphism . Many practical systems illustrate this effect, for example in designing methods for controlled drug delivery . In some cases, solubility equilibria can take

2706-408: Is observed to be almost an order of magnitude higher (i.e. about ten times higher) when the redox potential is controlled using a highly oxidizing Fe 3 O 4 -Fe 2 O 3 redox buffer than with a moderately oxidizing Ni - NiO buffer. Solubility (metastable, at concentrations approaching saturation) also depends on the physical size of the crystal or droplet of solute (or, strictly speaking, on

2788-434: Is the mole fraction of the i {\displaystyle i} -th component in the solution, P {\displaystyle P} is the pressure, the index T {\displaystyle T} refers to constant temperature, V i , a q {\displaystyle V_{i,aq}} is the partial molar volume of the i {\displaystyle i} -th component in

2870-421: Is the partial pressure (in atm), and c {\displaystyle c} is the concentration of the dissolved gas in the liquid (in mol/L). The solubility of gases is sometimes also quantified using Bunsen solubility coefficient . In the presence of small bubbles , the solubility of the gas does not depend on the bubble radius in any other way than through the effect of the radius on pressure (i.e.

2952-401: Is the same for all viewing angles, whereas structural color is the result of selective reflection or iridescence , usually because of multilayer structures. For example, butterfly wings typically contain structural color, although many butterflies have cells that contain pigment as well. Solubility In chemistry , solubility is the ability of a substance , the solute , to form

3034-536: Is used to approximate the true appearance. Gamut mapping trades off any one of lightness , hue , or saturation accuracy to render the color on screen, depending on the priority chosen in the conversion's ICC rendering intent . In biology , a pigment is any colored material of plant or animal cells. Many biological structures, such as skin , eyes , fur , and hair contain pigments (such as melanin ). Animal skin coloration often comes about through specialized cells called chromatophores , which animals such as

3116-480: Is used to quantify the solubility of gases in solvents. The solubility of a gas in a solvent is directly proportional to the partial pressure of that gas above the solvent. This relationship is similar to Raoult's law and can be written as: where k H {\displaystyle k_{\rm {H}}} is a temperature-dependent constant (for example, 769.2 L · atm / mol for dioxygen (O 2 ) in water at 298 K), p {\displaystyle p}

3198-433: Is usually mixed from Phthalo Blue and titanium dioxide , or from inexpensive synthetic blue dyes. The discovery in 1856 of mauveine , the first aniline dyes , was a forerunner for the development of hundreds of synthetic dyes and pigments like azo and diazo compounds. These dyes ushered in the flourishing of organic chemistry, including systematic designs of colorants. The development of organic chemistry diminished

3280-417: Is widely used across diverse media. Reference standards are provided by printed swatches of color shades. PANTONE , RAL , Munsell , etc. are widely used standards of color communication across diverse media like printing, plastics, and textiles . Companies manufacturing color masterbatches and pigments for plastics offer plastic swatches in injection molded color chips. These color chips are supplied to

3362-592: The 4th Dynasty . It was the blue pigment par excellence of Roman antiquity ; its art technological traces vanished in the course of the Middle Ages until its rediscovery in the context of the Egyptian campaign and the excavations in Pompeii and Herculaneum . Later premodern synthetic pigments include white lead (basic lead carbonate, (PbCO 3 ) 2 Pb(OH) 2 ), vermilion , verdigris , and lead-tin yellow . Vermilion,

Rubric - Misplaced Pages Continue

3444-683: The Colour Index International (CII) as a standard for identifying the pigments that they use in manufacturing particular colors. First published in 1925—and now published jointly on the web by the Society of Dyers and Colourists ( United Kingdom ) and the American Association of Textile Chemists and Colorists (US)—this index is recognized internationally as the authoritative reference on colorants. It encompasses more than 27,000 products under more than 13,000 generic color index names. In

3526-626: The Kelmscott Press at the end of the 19th century included chapter titles and other accents in red, or rarely blue, ink, and was influential on small press art typography associated with the Arts and Crafts movement in both England and the United States , particularly the work of the Ashendene , Doves , and Roycroft Presses. Around 1900, rubrication was incorporated into a Red letter edition of

3608-620: The Munsell color system became the foundation for a series of color models, providing objective methods for the measurement of color. The Munsell system describes a color in three dimensions, hue , value (lightness), and chroma (color purity), where chroma is the difference from gray at a given hue and value. By the middle 20th century, standardized methods for pigment chemistry were available, part of an international movement to create such standards in industry. The International Organization for Standardization (ISO) develops technical standards for

3690-497: The critical temperature ), the solubility of ionic solutes tends to decrease due to the change of properties and structure of liquid water; the lower dielectric constant results in a less polar solvent and in a change of hydration energy affecting the Δ G of the dissolution reaction. Gaseous solutes exhibit more complex behavior with temperature. As the temperature is raised, gases usually become less soluble in water (exothermic dissolution reaction related to their hydration) (to

3772-485: The hydrophobic effect . The free energy of dissolution ( Gibbs energy ) depends on temperature and is given by the relationship: Δ G = Δ H – TΔ S . Smaller Δ G means greater solubility. Chemists often exploit differences in solubilities to separate and purify compounds from reaction mixtures, using the technique of liquid-liquid extraction . This applies in vast areas of chemistry from drug synthesis to spent nuclear fuel reprocessing. Dissolution

3854-427: The mass fraction at equilibrium (mass of solute per mass of solute plus solvent). Both are dimensionless numbers between 0 and 1 which may be expressed as percentages (%). For solutions of liquids or gases in liquids, the quantities of both substances may be given volume rather than mass or mole amount; such as litre of solute per litre of solvent, or litre of solute per litre of solution. The value may be given as

3936-612: The octopus and chameleon can control to vary the animal's color. Many conditions affect the levels or nature of pigments in plant, animal, some protista , or fungus cells. For instance, the disorder called albinism affects the level of melanin production in animals. Pigmentation in organisms serves many biological purposes, including camouflage , mimicry , aposematism (warning), sexual selection and other forms of signalling , photosynthesis (in plants), and basic physical purposes such as protection from sunburn . Pigment color differs from structural color in that pigment color

4018-412: The reagents have been dissolved in a suitable solvent. Water is by far the most common such solvent. The term "soluble" is sometimes used for materials that can form colloidal suspensions of very fine solid particles in a liquid. The quantitative solubility of such substances is generally not well-defined, however. The solubility of a specific solute in a specific solvent is generally expressed as

4100-518: The specific surface area or molar surface area of the solute). For quantification, see the equation in the article on solubility equilibrium . For highly defective crystals, solubility may increase with the increasing degree of disorder. Both of these effects occur because of the dependence of solubility constant on the Gibbs energy of the crystal. The last two effects, although often difficult to measure, are of practical importance. For example, they provide

4182-475: The CII schema, each pigment has a generic index number that identifies it chemically, regardless of proprietary and historic names. For example, Phthalocyanine Blue BN has been known by a variety of generic and proprietary names since its discovery in the 1930s. In much of Europe, phthalocyanine blue is better known as Helio Blue, or by a proprietary name such as Winsor Blue. An American paint manufacturer, Grumbacher, registered an alternate spelling (Thanos Blue) as

SECTION 50

#1732845226317

4264-491: The Earth orbit and its rotation axis progressively change and modify the solar irradiance at the Earth surface, temperature starts to increase. When a deglaciation period is initiated, the progressive warming of the oceans releases CO 2 into the atmosphere because of its lower solubility in warmer sea water. In turn, higher levels of CO 2 in the atmosphere increase the greenhouse effect and carbon dioxide acts as an amplifier of

4346-559: The King James Version of the Bible to distinguish the Dominical words, i.e., those spoken by Jesus Christ during His corporeal life on Earth, because that translation lacked quotation marks. Other versions of the Bible have since adopted the popular practice. A rubric is an explicit set of criteria used for assessing a particular type of work or performance and provides more details than

4428-461: The Noyes-Whitney equation. Solubility constants are used to describe saturated solutions of ionic compounds of relatively low solubility (see solubility equilibrium ). The solubility constant is a special case of an equilibrium constant . Since it is a product of ion concentrations in equilibrium, it is also known as the solubility product . It describes the balance between dissolved ions from

4510-791: The concentration of a saturated solution of the two. Any of the several ways of expressing concentration of solutions can be used, such as the mass , volume , or amount in moles of the solute for a specific mass, volume, or mole amount of the solvent or of the solution. In particular, chemical handbooks often express the solubility as grams of solute per 100 millilitres of solvent (g/(100 mL), often written as g/100 ml), or as grams of solute per decilitre of solvent (g/dL); or, less commonly, as grams of solute per litre of solvent (g/L). The quantity of solvent can instead be expressed in mass, as grams of solute per 100 grams of solvent (g/(100 g), often written as g/100 g), or as grams of solute per kilogram of solvent (g/kg). The number may be expressed as

4592-471: The concentration of the solute can exceed its usual solubility limit. The result is a supersaturated solution , which is metastable and will rapidly exclude the excess solute if a suitable nucleation site appears. The concept of solubility does not apply when there is an irreversible chemical reaction between the two substances, such as the reaction of calcium hydroxide with hydrochloric acid ; even though one might say, informally, that one "dissolved"

4674-411: The dependence on inorganic pigments. Before the development of synthetic pigments, and the refinement of techniques for extracting mineral pigments, batches of color were often inconsistent. With the development of a modern color industry, manufacturers and professionals have cooperated to create international standards for identifying, producing, measuring, and testing colors. First published in 1905,

4756-441: The designer or customer to choose and select the color for their specific plastic products. Plastic swatches are available in various special effects like pearl, metallic, fluorescent, sparkle, mosaic etc. However, these effects are difficult to replicate on other media like print and computer display. Plastic swatches have been created by 3D modelling to including various special effects. The appearance of pigments in natural light

4838-402: The driving force for precipitate aging (the crystal size spontaneously increasing with time). The solubility of a given solute in a given solvent is function of temperature. Depending on the change in enthalpy (Δ H ) of the dissolution reaction, i.e. , on the endothermic (Δ H  > 0) or exothermic (Δ H  < 0) character of the dissolution reaction, the solubility of

4920-399: The easiest to synthesize, and chemists created modern colors based on the originals. These were more consistent than colors mined from the original ore bodies, but the place names remained. Also found in many Paleolithic and Neolithic cave paintings are Red Ochre, anhydrous Fe 2 O 3 , and the hydrated Yellow Ochre (Fe 2 O 3 H 2 O). Charcoal—or carbon black—has also been used as

5002-418: The estimated value of the pigment industry globally is $ 30 billion. The value of titanium dioxide – used to enhance the white brightness of many products – was placed at $ 13.2 billion per year, while the color Ferrari red is valued at $ 300 million each year. Like all materials, the color of pigments arises because they absorb only certain wavelengths of visible light . The bonding properties of

SECTION 60

#1732845226317

5084-493: The extent of solubility for a given application. For example, U.S. Pharmacopoeia gives the following terms, according to the mass m sv of solvent required to dissolve one unit of mass m su of solute: (The solubilities of the examples are approximate, for water at 20–25 °C.) The thresholds to describe something as insoluble, or similar terms, may depend on the application. For example, one source states that substances are described as "insoluble" when their solubility

5166-551: The first millennium it appears that written versions existed. Full rubrics regarding matters such as vesture , appearance of the altar , timing of specific liturgies, and similar matters still may be published separately. In modern liturgical books, e.g. the Catholic Roman Missal , lengthy general rubrics, probably printed in black, pertain to such matters and preface the actual order of liturgies, which contain shorter, specific rubrics that still are usually rubricated. Red

5248-443: The gaseous state first. The solubility mainly depends on the composition of solute and solvent (including their pH and the presence of other dissolved substances) as well as on temperature and pressure. The dependency can often be explained in terms of interactions between the particles ( atoms , molecules , or ions ) of the two substances, and of thermodynamic concepts such as enthalpy and entropy . Under certain conditions,

5330-479: The general warming. A popular aphorism used for predicting solubility is " like dissolves like " also expressed in the Latin language as " Similia similibus solventur ". This statement indicates that a solute will dissolve best in a solvent that has a similar chemical structure to itself, based on favorable entropy of mixing . This view is simplistic, but it is a useful rule of thumb. The overall solvation capacity of

5412-497: The manufacture of pigments and dyes. ISO standards define various industrial and chemical properties, and how to test for them. The principal ISO standards that relate to all pigments are as follows: Other ISO standards pertain to particular classes or categories of pigments, based on their chemical composition, such as ultramarine pigments, titanium dioxide , iron oxide pigments, and so forth. Many manufacturers of paints, inks, textiles, plastics, and colors have voluntarily adopted

5494-570: The material determine the wavelength and efficiency of light absorption. Light of other wavelengths are reflected or scattered. The reflected light spectrum defines the color that we observe. The appearance of pigments is sensitive to the source light. Sunlight has a high color temperature and a fairly uniform spectrum. Sunlight is considered a standard for white light. Artificial light sources are less uniform. Color spaces used to represent colors numerically must specify their light source. Lab color measurements, unless otherwise noted, assume that

5576-559: The measurement was recorded under a D65 light source, or "Daylight 6500 K", which is roughly the color temperature of sunlight. Other properties of a color, such as its saturation or lightness, may be determined by the other substances that accompany pigments. Binders and fillers can affect the color. Minerals have been used as colorants since prehistoric times. Early humans used paint for aesthetic purposes such as body decoration. Pigments and paint grinding equipment believed to be between 350,000 and 400,000 years old have been reported in

5658-672: The other. The solubility is also not the same as the rate of solution , which is how fast a solid solute dissolves in a liquid solvent. This property depends on many other variables, such as the physical form of the two substances and the manner and intensity of mixing. The concept and measure of solubility are extremely important in many sciences besides chemistry, such as geology , biology , physics , and oceanography , as well as in engineering , medicine , agriculture , and even in non-technical activities like painting , cleaning , cooking , and brewing . Most chemical reactions of scientific, industrial, or practical interest only happen after

5740-459: The practice of harvesting Indian yellow was eventually declared to be inhumane. Modern hues of Indian yellow are made from synthetic pigments. Vermillion has been partially replaced in by cadmium reds. Because of the cost of lapis lazuli , substitutes were often used. Prussian blue , the oldest modern synthetic pigment, was discovered by accident in 1704. By the early 19th century, synthetic and metallic blue pigments included French ultramarine ,

5822-433: The reference value, the hue is also systematically biased. The following approximations assume a display device at gamma 2.2, using the sRGB color space . The further a display device deviates from these standards, the less accurate these swatches will be. Swatches are based on the average measurements of several lots of single-pigment watercolor paints, converted from Lab color space to sRGB color space for viewing on

5904-405: The salt and undissolved salt. The solubility constant is also "applicable" (i.e. useful) to precipitation , the reverse of the dissolving reaction. As with other equilibrium constants, temperature can affect the numerical value of solubility constant. While the solubility constant is not as simple as solubility, the value of this constant is generally independent of the presence of other species in

5986-444: The set phrase "under [whatever] rubric", for example, "under this rubric, [X is true]", or "[X was done] under the rubric of Y". Such senses include: "an authoritative rule"; "the title of a statute"; "something under which a thing is classed" ; "an explanatory or introductory commentary" ; "an established rule, tradition, or custom"; or "a guide listing specific criteria for grading or scoring academic assignments" . Instructions for

6068-414: The solubility of gas in the liquid in contact with small bubbles is increased due to pressure increase by Δ p  = 2γ/ r ; see Young–Laplace equation ). Henry's law is valid for gases that do not undergo change of chemical speciation on dissolution. Sieverts' law shows a case when this assumption does not hold. The carbon dioxide solubility in seawater is also affected by temperature, pH of

6150-483: The solubility per mole of solution is usually computed and quoted as if the solute does not dissociate or form complexes—that is, by pretending that the mole amount of solution is the sum of the mole amounts of the two substances. The extent of solubility ranges widely, from infinitely soluble (without limit, i.e. miscible ) such as ethanol in water, to essentially insoluble, such as titanium dioxide in water. A number of other descriptive terms are also used to qualify

6232-453: The solute is not recovered upon evaporation of the solvent, the process is referred to as solvolysis. The thermodynamic concept of solubility does not apply straightforwardly to solvolysis. When a solute dissolves, it may form several species in the solution. For example, an aqueous solution of cobalt(II) chloride can afford [Co(H 2 O) 6 ] , [CoCl(H 2 O) 5 ] , CoCl 2 (H 2 O) 2 , each of which interconverts. Solubility

6314-587: The solution, V i , c r {\displaystyle V_{i,cr}} is the partial molar volume of the i {\displaystyle i} -th component in the dissolving solid, and R {\displaystyle R} is the universal gas constant . The pressure dependence of solubility does occasionally have practical significance. For example, precipitation fouling of oil fields and wells by calcium sulfate (which decreases its solubility with decreasing pressure) can result in decreased productivity with time. Henry's law

6396-557: The solution, and by the carbonate buffer. The decrease of solubility of carbon dioxide in seawater when temperature increases is also an important retroaction factor (positive feedback) exacerbating past and future climate changes as observed in ice cores from the Vostok site in Antarctica . At the geological time scale, because of the Milankovich cycles , when the astronomical parameters of

6478-409: The solvation. Factors such as temperature and pressure will alter this balance, thus changing the solubility. Solubility may also strongly depend on the presence of other species dissolved in the solvent, for example, complex-forming anions ( ligands ) in liquids. Solubility will also depend on the excess or deficiency of a common ion in the solution , a phenomenon known as the common-ion effect . To

6560-415: The solvent and the sum of the two volumes. Moreover, many solids (such as acids and salts ) will dissociate in non-trivial ways when dissolved; conversely, the solvent may form coordination complexes with the molecules or ions of the solute. In those cases, the sum of the moles of molecules of solute and solvent is not really the total moles of independent particles solution. To sidestep that problem,

6642-441: The solvent is removed, all of the substance that had dissolved is recovered. The term solubility is also used in some fields where the solute is altered by solvolysis . For example, many metals and their oxides are said to be "soluble in hydrochloric acid", although in fact the aqueous acid irreversibly degrades the solid to give soluble products. Most ionic solids dissociate when dissolved in polar solvents. In those cases where

6724-403: The two substances are said to be " miscible in all proportions" (or just "miscible"). The solute can be a solid , a liquid , or a gas , while the solvent is usually solid or liquid. Both may be pure substances, or may themselves be solutions. Gases are always miscible in all proportions, except in very extreme situations, and a solid or liquid can be "dissolved" in a gas only by passing into

#316683