|
Rubber Policeman
A policeman is a hand-held flexible natural-rubber or plastic scraper. The common type of it is attached to a glass rod and used in chemical laboratories to transfer residues of precipitate or solid on glass surfaces when performing gravimetric analysis. This equipment works well under gentle, delicate and precise requirement. A policeman also comes in various sizes, shapes, and types. Some of them come in one-piece flexible plastic version and some in stainless. The origin of the policeman and its name cannot be identified for sure but some clues led back to the 19th century from the chemist named Carl Remigius Fresenius. Origin In chemistry, gravimetric analysis is essential. After precipitating the chemical element of interest, successfully transfer all of the precipitate to the filtration funnel for separation from the supernatant liquid is required. Normally, it used to be done by using a stream of distilled water from a wash bottle. However, such a way is ineffective beca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical
A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., without breaking chemical bonds. Chemical substances can be simple substances (substances consisting of a single chemical element), chemical compounds, or alloys. Chemical substances are often called 'pure' to set them apart from mixtures. A common example of a chemical substance is pure water; it has the same properties and the same ratio of hydrogen to oxygen whether it is isolated from a river or made in a laboratory. Other chemical substances commonly encountered in pure form are diamond (carbon), gold, table salt (sodium chloride) and refined sugar (sucrose). However, in practice, no substance is entirely pure, and chemical purity is specified according to the intended use of the chemical. Chemical substances exist as solids, liquids, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laboratories
A laboratory (; ; colloquially lab) is a facility that provides controlled conditions in which scientific or technological research, experiments, and measurement may be performed. Laboratory services are provided in a variety of settings: physicians' offices, clinics, hospitals, and regional and national referral centers. Overview The organisation and contents of laboratories are determined by the differing requirements of the specialists working within. A physics laboratory might contain a particle accelerator or vacuum chamber, while a metallurgy laboratory could have apparatus for casting or refining metals or for testing their strength. A chemist or biologist might use a wet laboratory, while a psychologist's laboratory might be a room with one-way mirrors and hidden cameras in which to observe behavior. In some laboratories, such as those commonly used by computer scientists, computers (sometimes supercomputers) are used for either simulations or the analysis of data. Scienti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 to precipitation, the chemical reagent causing the solid to form is called the ''precipitant''. The clear liquid remaining above the precipitated or the centrifuged solid phase is also called the 'supernate' or 'supernatant'. The notion of precipitation can also be extended to other domains of chemistry (organic chemistry and biochemistry) and even be applied to the solid phases (''e.g.'', metallurgy and alloys) when solid impurities segregate from a solid phase. Supersaturation The precipitation of a compound may occur when its concentration exceeds its solubility. This can be due to temperature changes, solvent evaporation, or by mixing solvents. Precipitation occurs more rapidly from a strongly supersaturated solution. The formati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravimetric Analysis
Gravimetric analysis describes a set of methods used in analytical chemistry for the quantitative determination of an analyte (the ion being analyzed) based on its mass. The principle of this type of analysis is that once an ion's mass has been determined as a unique compound, that known measurement can then be used to determine the same analyte's mass in a mixture, as long as the relative quantities of the other constituents are known. The four main types of this method of analysis are ''precipitation'', ''volatilization'', ''electro-analytical'' and ''miscellaneous physical method''. The methods involve changing the phase of the analyte to separate it in its pure form from the original mixture and are quantitative measurements. Precipitation method The precipitation method is the one used for the determination of the amount of calcium in water. Using this method, an excess of oxalic acid, H2C2O4, is added to a measured, known volume of water. By adding a reagent, here ammoni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carl Remigius Fresenius
Carl Remigius Fresenius (28 December 1818 – 11 June 1897), was a German chemist, known for his studies in analytical chemistry. Biography Fresenius was born on 28 December 1818, in Frankfurt, Germany. After working for some time for a pharmacy in his native town, he entered Bonn University in 1840, and a year later migrated to Gießen, where he acted as assistant in Liebig's laboratory, and in 1843, became an assistant professor. In 1845, he was appointed to the chair of chemistry, physics and technology at the Wiesbaden Agricultural Institution, and three years later, he became the first director of the chemical laboratory which he induced the Nassau government to establish at that place. Under his leadership and direction, this laboratory continuously increased in size and popularity, a school of pharmacy being added in 1862 (though given up in 1877) and an agricultural research laboratory in 1868. Apart from his administrative duties, Fresenius occupied himself almost ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Filtration
Filtration is a physical separation process that separates solid matter and fluid from a mixture using a ''filter medium'' that has a complex structure through which only the fluid can pass. Solid particles that cannot pass through the filter medium are described as ''oversize'' and the fluid that passes through is called the ''filtrate''. Oversize particles may form a filter cake on top of the filter and may also block the filter lattice, preventing the fluid phase from crossing the filter, known as ''blinding''. The size of the largest particles that can successfully pass through a filter is called the effective ''pore size'' of that filter. The separation of solid and fluid is imperfect; solids will be contaminated with some fluid and filtrate will contain fine particles (depending on the pore size, filter thickness and biological activity). Filtration occurs both in nature and in engineered systems; there are biological, geological, and industrial forms. Filtration is als ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wash Bottle
A wash bottle is a squeeze bottle with a nozzle, used to rinse various pieces of laboratory glassware, such as test tubes and round bottom flasks. Wash bottles are sealed with a screw-top lid. When hand pressure is applied to the bottle, the liquid inside becomes pressurized and is forced out of the nozzle into a narrow stream of liquid. Most wash bottles are made up of polyethylene, which is a flexible solvent-resistant petroleum-based plastic. Most bottles contain an internal dip tube allowing upright use. Wash bottles may be filled with a range of common laboratory solvents and reagents, according to the work to be undertaken. These include deionized water, detergent solutions and rinse solvents such as acetone, isopropanol or ethanol. In biological labs it is common to keep sodium hypochlorite solution in a wash bottle to disinfect unneeded cultures. Colour codes on wash bottles There are a consistent set of colour codes and markings used to identify the contents of wash ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plastic Policeman
Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptability, plus a wide range of other properties, such as being lightweight, durable, flexible, and inexpensive to produce, has led to its widespread use. Plastics typically are made through human industrial systems. Most modern plastics are derived from fossil fuel-based chemicals like natural gas or petroleum; however, recent industrial methods use variants made from renewable materials, such as corn or cotton derivatives. 9.2 billion tonnes of plastic are estimated to have been made between 1950 and 2017. More than half this plastic has been produced since 2004. In 2020, 400 million tonnes of plastic were produced. If global trends on plastic demand continue, it is estimated that by 2050 annual global plastic production will reach over 1,100 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stainless Laboratory Spatula , the second national flag of the Confederate States of America
{{Disambiguation ...
Stainless may refer to: * Stainless steel, a corrosion-resistant metal alloy * Stainless Games, a British video game developer * Stainless Broadcasting Company, a TV broadcaster based in Michigan, US * Stainless Banner The flags of the Confederate States of America have a history of three successive designs during the American Civil War. The flags were known as the "Stars and Bars", used from 1861 to 1863; the "Stainless Banner", used from 1863 to 1865; and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Use Of A Plastic Policeman
''The'' () is a grammatical article in English, denoting persons or things that are already or about to be mentioned, under discussion, implied or otherwise presumed familiar to listeners, readers, or speakers. It is the definite article in English. ''The'' is the most frequently used word in the English language; studies and analyses of texts have found it to account for seven percent of all printed English-language words. It is derived from gendered articles in Old English which combined in Middle English and now has a single form used with nouns of any gender. The word can be used with both singular and plural nouns, and with a noun that starts with any letter. This is different from many other languages, which have different forms of the definite article for different genders or numbers. Pronunciation In most dialects, "the" is pronounced as (with the voiced dental fricative followed by a schwa) when followed by a consonant sound, and as (homophone of the archaic pron ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glass Rod
A glass stirring rod, glass rod, stirring rod or stir rod is a piece of laboratory equipment used to mix chemicals. They are usually made of solid glass, about the thickness and slightly longer than a drinking straw, with rounded ends. Structure Stir rods are generally made of borosilicate (commonly known as Pyrex) glass or polypropylene plastic. They are usually between 10 and 40 centimeters in length and about half a centimeter in diameter. Glass rods are created from a single length of thin glass that is then cut into smaller segments. The ends are generally rounded (for example, by flame polishing) to prevent scratching the surface of glassware during use, which may lead to cracks if the glassware is later heated. Other shapes are possible, such as a flat paddle which can be used to circulate sediment, a triangular paddle to imitate a rubber policeman or a round button used to crush solids. Uses A stirring rod is used for mixing liquids, or solids and liquids. Stir rods ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
.png "Click for more on -> The Use Of A Plastic Policeman")
