|
Deniges' Method
A range of qualitative and quantitative tests have been developed to detect phosphate ions (PO43-) in solution. Such tests find use in industrial processes, scientific research, and environmental water monitoring. Quantitative method A quantitative method to determine the amount of phosphate present in samples, such as boiler feedwater, is as follows. A measured amount of boiler water is poured into a mixing tube and ammonium heptamolybdate reagent is added. The tube is then stoppered and vigorously shaken. The next step is to add dilute stannous chloride reagent, which has been freshly prepared from concentrated stannous chloride reagent and distilled water, to the mixture in the tube. This will produce a blue colour (due to the formation of molybdenum blue) and the depth of the blue colour indicates the amount of phosphate in the boiler water. The absorbance of the blue solution can be measured with a colorimeter and the concentration of phosphate in the original solution can b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Environmental Monitoring
Environmental monitoring describes the processes and activities that need to take place to characterize and monitor the quality of the environment. Environmental monitoring is used in the preparation of environmental impact assessments, as well as in many circumstances in which human activities carry a risk of harmful effects on the natural environment. All monitoring strategies and programs have reasons and justifications which are often designed to establish the current status of an environment or to establish trends in environmental parameters. In all cases, the results of monitoring will be reviewed, analyzed statistically, and published. The design of a monitoring program must therefore have regard to the final use of the data before monitoring starts. Environmental monitoring includes monitoring of air quality, soils and water quality. Air quality monitoring Air pollutants are atmospheric substances—both naturally occurring and anthropogenic—which may potentially ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phosphate
In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phosphoric acid by the removal of three protons . Removal of one or two protons gives the dihydrogen phosphate ion and the hydrogen phosphate ion ion, respectively. These names are also used for salts of those anions, such as ammonium dihydrogen phosphate and trisodium phosphate. File:3-phosphoric-acid-3D-balls.png, Phosphoricacid File:2-dihydrogenphosphate-3D-balls.png, Dihydrogenphosphate File:1-hydrogenphosphate-3D-balls.png, Hydrogenphosphate File:0-phosphate-3D-balls.png, Phosphate In organic chemistry, phosphate or orthophosphate is an organophosphate, an ester of orthophosphoric acid of the form where one or more hydrogen atoms are replaced by organic groups. An example is trimethyl phosphate, . The term also refers to the triv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boiler Feedwater
Boiler feedwater is an essential part of boiler operations. The feed water is put into the steam drum from a feed pump. In the steam drum the feed water is then turned into steam from the heat. After the steam is used it is then dumped to the main condenser. From the condenser it is then pumped to the deaerated feed tank. From this tank it then goes back to the steam drum to complete its cycle. The feed water is never open to the atmosphere. This cycle is known as a closed system or Rankine cycle. History of feedwater treatment During the early development of boilers, water treatment was not so much of an issue, as temperatures and pressures were so low that high amounts of scale and rust would not form to such a significant extent, especially if the boiler was “ blown down”. It was general practice to install zinc plates and/or alkaline chemicals to reduce corrosion within the boiler. Many tests had been performed to determine the cause (and possible protection) from corrosi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ammonium Heptamolybdate
Ammonium heptamolybdate is the inorganic compound whose chemical formula is (NH4)6Mo7O24, normally encountered as the tetrahydrate. A dihydrate is also known. It is a colorless solid, often referred to as ammonium paramolybdate or simply as ammonium molybdate, although "ammonium molybdate" can also refer to ammonium orthomolybdate, (NH4)2MoO4, and several other compounds. It is one of the more common molybdenum compounds. Synthesis Ammonium heptamolybdate is easily prepared by dissolving molybdenum trioxide in an excess of aqueous ammonia and evaporating the solution at room temperature. While the solution evaporates, the excess of ammonia escapes. This method results in the formation of six-sided transparent prisms of the tetrahydrate of ammonium heptamolybdate. Solutions of ammonium paramolybdate react with acids to form molybdic acid and an ammonium salt. The pH value of a concentrated solution will lie between 5 and 6. Structure The compound was first analyzed crystallogra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stannous Chloride
Tin(II) chloride, also known as stannous chloride, is a white crystalline solid with the formula . It forms a stable dihydrate, but aqueous solutions tend to undergo hydrolysis, particularly if hot. SnCl2 is widely used as a reducing agent (in acid solution), and in electrolytic baths for tin-plating. Tin(II) chloride should not be confused with the other chloride of tin; tin(IV) chloride or stannic chloride (SnCl4). Chemical structure SnCl2 has a lone pair of electrons, such that the molecule in the gas phase is bent. In the solid state, crystalline SnCl2 forms chains linked via chloride bridges as shown. The dihydrate is also three-coordinate, with one water coordinated on to the tin, and a second water coordinated to the first. The main part of the molecule stacks into double layers in the crystal lattice, with the "second" water sandwiched between the layers. Chemical properties Tin(II) chloride can dissolve in less than its own mass of water without apparent decomposition ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molybdenum Blue
Molybdenum blue is a term applied to: *reduced heteropolymolybdate complexes, polyoxometalates containing Mo(V), Mo(VI), and a hetero atom such as phosphorus or silicon *reduced isopolymolybdate complexes, polyoxometalates containing Mo(V), Mo(VI) formed when solutions of Mo(VI) are reduced *a blue pigment containing molybdenum(VI) oxide The "heteropoly-molybdenum blues", are used extensively in analytical chemistry and as catalysts. The formation of "isopoly-molybdenum blues" which are intense blue has been used as a sensitive test for reducing reagents. They have recently been shown to contain very large anionic species based on the so-called "big wheel" containing 154 Mo atoms, with a formula o154O462H14(H2O)70sup>14−.''From Scheele and Berzelius to MÜller: polyoxometalates (POMs) revisited and the "missing link" between the bottom up and top down approaches'' P. Gouzerh, M. Che; ''L'Actualité Chimique'', 2006, 298, 9 The molybdenum blue pigment is historically documented' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Absorbance
Absorbance is defined as "the logarithm of the ratio of incident to transmitted radiant power through a sample (excluding the effects on cell walls)". Alternatively, for samples which scatter light, absorbance may be defined as "the negative logarithm of one minus absorptance, as measured on a uniform sample". The term is used in many technical areas to quantify the results of an experimental measurement. While the term has its origin in quantifying the absorption of light, it is often entangled with quantification of light which is “lost” to a detector system through other mechanisms. What these uses of the term tend to have in common is that they refer to a logarithm of the ratio of a quantity of light incident on a sample or material to that which is detected after the light has interacted with the sample. The term absorption refers to the physical process of absorbing light, while absorbance does not always measure only absorption; it may measure attenuation (of trans ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Colorimeter (chemistry)
A colorimeter is a device used in Colorimetry (chemical method), colorimetry that measures the absorbance of particular wavelengths of light by a specific Solution (chemistry), solution. It is commonly used to determine the concentration of a known solute in a given solution by the application of the Beer–Lambert law, which states that the concentration of a solute is proportional to the absorbance. Construction The essential parts of a colorimeter are: * a light source (often an ordinary low-voltage filament lamp); * an adjustable aperture; * a set of colored Filter (optics), filters; * a cuvette to hold the working solution; * a detector (usually a photoresistor) to measure the transmitted light; * a meter to display the output from the detector. In addition, there may be: * a voltage regulator, to protect the instrument from fluctuations in Mains power systems, mains voltage; * a second light path, cuvette and detector. This enables comparison between the working solut ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lovibond Comparator
The Lovibond comparator is an example of a colorimeter made in Britain by The Tintometer Ltd. It was invented in the 19th century by Joseph Williams Lovibond anupdated versionsare still available. Description The device is used to determine the color of liquids. A sample is put in a glass tube. The tube is inserted in the comparator and compared with a series of coloured glass discs until the nearest possible match is found. Among other things, the device is used to determine the concentration of certain chemicals in solution. In this use, some assumptions are made about what is in the sample. Given those assumptions, the concentration will be indicated by the disc which best matches the color of the solution. There are a number of standard tests in which a sample to be tested is mixed a colour reagent. In such tests, the resulting color indicates the concentration of the sample under test. Results can be approximate compared to other testing techniques, but the comparator i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitric Acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitric acid has a concentration of 68% in water. When the solution contains more than 86% , it is referred to as ''fuming nitric acid''. Depending on the amount of nitrogen dioxide present, fuming nitric acid is further characterized as red fuming nitric acid at concentrations above 86%, or white fuming nitric acid at concentrations above 95%. Nitric acid is the primary reagent used for nitration – the addition of a nitro group, typically to an organic molecule. While some resulting nitro compounds are shock- and thermally-sensitive explosives, a few are stable enough to be used in munitions and demolition, while others are still more stable and used as pigments in inks and dyes. Nitric acid is also commonly used as a strong oxidizing agen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ammonium Orthomolybdate
Ammonium orthomolybdate is the inorganic compound with the chemical formula (NH4)2MoO4. It is a white solid that is prepared by treating molybdenum trioxide with aqueous ammonia. Upon heating these solutions, ammonia is lost, to give ammonium heptamolybdate ((NH4)6Mo7O24·4H2O). Uses Ammonium orthomolybdate is used as a corrosion inhibitor and is an intermediate in some schemes to win molybdenum from its ores.Roger F. Sebenik et al. "Molybdenum and Molybdenum Compounds" in Ullmann's Encyclopedia of Chemical Technology 2005; Wiley-VCH, Weinheim. It is also used for decorating ceramics, and for colorimetric analysis of phosphates and arsenates. Chemical reactions Heating ammonium orthomolybdate solid or treatment with acid gives molybdenum trioxide. Such reactions proceed via ammonium dimolybdate. This equilibrium is exploited in the purification of molybdenum from its ores. Aqueous solutions of ammonium orthomolybdate react with hydrogen sulfide to give ammonium tetrathiomol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ammonium Phosphomolybdate
Ammonium phosphomolybdate is the inorganic salt of phosphomolybdic acid with the chemical formula (NH4)3PMo12O40. The salt contains the phosphomolybdate anion, a well known heteropolymetalate of the Keggin structural class. Synthesis Ammonium phosphomolybdate can be made by heating ammonium orthomolybdate combined with phosphoric acid and nitric acid, yielding ammonium nitrate, water, and a yellow precipitate In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading ... of ammonium phosphomolybdate is obtained. : Normally, it often is as a hexahydrate, which is a dark yellow fine crystal, and poorly soluble in water. References {{Ammonium salts Ammonium compounds Molybdates Inorganic phosphorus compounds Heteropoly acids ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
-chloride-xtal-1996-3D-balls-front.png "Click for more on -> Stannous Chloride")
