The kilogram or kilogramme is the base unit of mass in the International System of Units. Until 20 May 2019, it remains defined by a platinum alloy cylinder, the International Prototype Kilogram, manufactured in 1889, stored in Saint-Cloud, a suburb of Paris. After 20 May, it will be defined in terms of fundamental physical constants; the kilogram was defined as the mass of a litre of water. That was an inconvenient quantity to replicate, so in 1799 a platinum artefact was fashioned to define the kilogram; that artefact, the IPK, have been the standard of the unit of mass for the metric system since. In spite of best efforts to maintain it, the IPK has diverged from its replicas by 50 micrograms since their manufacture late in the 19th century; this led to efforts to develop measurement technology precise enough to allow replacing the kilogram artifact with a definition based directly on physical phenomena, now scheduled to take place in 2019. The new definition is based on invariant constants of nature, in particular the Planck constant, which will change to being defined rather than measured, thereby fixing the value of the kilogram in terms of the second and the metre, eliminating the need for the IPK.
The new definition was approved by the General Conference on Weights and Measures on 16 November 2018. The Planck constant relates a light particle's energy, hence mass, to its frequency; the new definition only became possible when instruments were devised to measure the Planck constant with sufficient accuracy based on the IPK definition of the kilogram. The gram, 1/1000 of a kilogram, was provisionally defined in 1795 as the mass of one cubic centimetre of water at the melting point of ice; the final kilogram, manufactured as a prototype in 1799 and from which the International Prototype Kilogram was derived in 1875, had a mass equal to the mass of 1 dm3 of water under atmospheric pressure and at the temperature of its maximum density, 4 °C. The kilogram is the only named SI unit with an SI prefix as part of its name; until the 2019 redefinition of SI base units, it was the last SI unit, still directly defined by an artefact rather than a fundamental physical property that could be independently reproduced in different laboratories.
Three other base units and 17 derived units in the SI system are defined in relation to the kilogram, thus its stability is important. The definitions of only eight other named SI units do not depend on the kilogram: those of temperature and frequency, angle; the IPK is used or handled. Copies of the IPK kept by national metrology laboratories around the world were compared with the IPK in 1889, 1948, 1989 to provide traceability of measurements of mass anywhere in the world back to the IPK; the International Prototype Kilogram was commissioned by the General Conference on Weights and Measures under the authority of the Metre Convention, in the custody of the International Bureau of Weights and Measures who hold it on behalf of the CGPM. After the International Prototype Kilogram had been found to vary in mass over time relative to its reproductions, the International Committee for Weights and Measures recommended in 2005 that the kilogram be redefined in terms of a fundamental constant of nature.
At its 2011 meeting, the CGPM agreed in principle that the kilogram should be redefined in terms of the Planck constant, h. The decision was deferred until 2014. CIPM has proposed revised definitions of the SI base units, for consideration at the 26th CGPM; the formal vote, which took place on 16 November 2018, approved the change, with the new definitions coming into force on 20 May 2019. The accepted redefinition defines the Planck constant as 6.62607015×10−34 kg⋅m2⋅s−1, thereby defining the kilogram in terms of the second and the metre. Since the second and metre are defined in terms of physical constants, the kilogram is defined in terms of physical constants only; the avoirdupois pound, used in both the imperial and US customary systems, is now defined in terms of the kilogram. Other traditional units of weight and mass around the world are now defined in terms of the kilogram, making the kilogram the primary standard for all units of mass on Earth; the word kilogramme or kilogram is derived from the French kilogramme, which itself was a learned coinage, prefixing the Greek stem of χίλιοι khilioi "a thousand" to gramma, a Late Latin term for "a small weight", itself from Greek γράμμα.
The word kilogramme was written into French law in 1795, in the Decree of 18 Germinal, which revised the older system of units introduced by the French National Convention in 1793, where the gravet had been defined as weight of a cubic centimetre of water, equal to 1/1000 of a grave. In the decree of 1795, the term gramme thus replaced gravet, kilogramme replaced grave; the French spelling was adopted in Great Britain when the word was used for the first time in English in 1795, with the spelling kilogram being adopted in the United States. In the United Kingdom both spellings are used, with "kilogram" having become by far the more common. UK law regulating the units to be used when trading by weight or measure does not prevent the use of either spelling. In the 19th century the French word kilo, a shortening of kilogramme, was imported into the English language where it has been used to mean both kilogram and kilometre. While kilo is acceptable in many generalist texts
A clamp is a fastening device used to hold or secure objects together to prevent movement or separation through the application of inward pressure. In the United Kingdom and Australia, the term cramp is used instead when the tool is for temporary use for positioning components during construction and woodworking. There are many types of clamps available for many different purposes; some are temporary, as used to position components while fixing them together, others are intended to be permanent. In the field of animal husbandry, using a clamp to attach an animal to a stationary object is known as "rounded clamping." A physical clamp of this type is used to refer to an obscure investment banking term. Anything that performs the action of clamping may be called a clamp, so this gives rise to a wide variety of terms across many fields; these clamps are used to position components temporarily for various tasks: Band clamp or web clamp Bar clamp, F-clamp or sliding clamp Bench clamp The bench forms the fixed jaw.
Cardellini clamp – jaw-style clamp that clamps onto round, square, or rectangular tubing. Forked clamp stainless steel for ST ground glass joints with/without setscrew. Sizes for: ST 14, 19, 24, 29 and 45. Gripe Handscrew Kant-Twist clamp Magnetic clamp Mitre clamp Pipe clamp Sash clamp Set screw Spring clamp Speed clamp Step clamp, a type of serrated-edged clamp used in conjunction with step blocks when machining or milling parts in metalworking Toggle clamp Toolmakers' clamp Pinch Dog Clip hangers are a subset of clothes hangers Hose clamp Marman clamp Wire rope clamp Joiner's dog Foerster clamp Hemostatic clamp Pennington clamp Gomco clamp Mogen clamp Wheel clamp Pandrol clip Tube clamp Nipple clamp Fixture Vise Patrick Spielman. Gluing and Clamping: A Woodworker’s Handbook. Sterling Publishing. ISBN 0-8069-6274-7 Lee Jesberger. Pro Woodworking Tips
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, 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. There are a consistent set of colour codes and markings used to identify the contents of wash bottles. Red is used for acetone, White for ethanol or sodium hypochlorite, green for Methanol is yellow for isopropanol and blue for distilled water.
Safety warning labels are used to identify potential hazards. Where reagents with high vapour pressure are used such as ethanol or methanol, small pressure release holes are incorporated into the cap to release and excess vapour pressure and avoid material being ejected through the nozzle when not in use; the use of wash bottles helps rusers measure the precise amount of liquid used. In addition, unwanted substances or particles cannot pass through wash bottles; the use of wash bottles is more convenient than using graduated cylinders. Wash bottles are kept on the laboratory bench in a secure way so that they can be located and so that they do not interfere with other work taking place; such containment may be by the use of two ring clamps which have similar size attached to a lattice rod. Different types of wash bottles are suitable with different types of substances. A spiral gas-lift wash bottle, for example, is suitable for eliminating gas with the liquid system having two phases like bromide and water.
In addition, a Simple graduated. A type of strong solvent and a type of destructive substance can be dealt with Nalgene Teflon FEP wash bottles since the special type of plastic is used to produce this type of wash bottles. Squeeze bottle
Incubator is a device used to grow and maintain microbiological cultures or cell cultures. The incubator maintains optimal temperature and other conditions such as the CO and oxygen content of the atmosphere inside. Incubators are essential for a lot of experimental work in cell biology and molecular biology and are used to culture both bacterial as well as eukaryotic cells. Louis Pasteur used the small opening underneath his staircase as an incubator. Incubators are used in the poultry industry to act as a substitute for hens; this results in higher hatch rates due to the ability to control both temperature and humidity. Various brands of incubators are commercially available to breeders; the simplest incubators are insulated boxes with an adjustable heater going up to 60 to 65 °C, though some can go higher. The most used temperature both for bacteria such as the used E. coli as well as for mammalian cells is 37 °C, as these organisms grow well under such conditions. For other organisms used in biological experiments, such as the budding yeast Saccharomyces cerevisiae, a growth temperature of 30 °C is optimal.
More elaborate incubators can include the ability to lower the temperature, or the ability to control humidity or CO2 levels. This is important in the cultivation of mammalian cells, where the relative humidity is >80% to prevent evaporation and a acidic pH is achieved by maintaining a CO2 level of 5%. From aiding in hatching chicken eggs to enabling scientists to understand and develop vaccines for deadly viruses, the laboratory incubator has seen numerous applications over the thousands of years it has been in use; the incubator has provided a foundation for medical advances and experimental work in cellular and molecular biology. An incubator is made up of a chamber with a regulated temperature; some incubators regulate humidity, gas composition, or ventilation within that chamber. While many technological advances have occurred since the primitive incubators first used in ancient Egypt and China, the main purpose of the incubator has remained unchanged: to create a stable, controlled environment conducive to research and cultivation.
The earliest incubators were found thousands of years ago in ancient Egypt and China, where they were used to keep chicken eggs warm.. Use of incubators revolutionized food production, as it allowed chicks to hatch from eggs without requiring that a hen sit on them, thus freeing the hens to lay more eggs in a shorter period of time. Both early Egyptian and Chinese incubators were large rooms that were heated by fires, where attendants turned the eggs at regular intervals to ensure heat distribution.. The incubator received an update in the 16th century when Jean Baptiste Porta drew on ancient Egyptian design to create a more modern egg incubator. While he had to discontinue his work due to the Spanish Inquisition, Rene-Antoine Ferchault de Reaumur took up the challenge in the middle of the 17th century. Reaumur warmed his incubator with a wood stove and monitored its temperature using the Reaumur thermometer, another of his inventions. In the 19th century, researchers began to recognize that the use of incubators could contribute to medical advancements.
They began to experiment to find the ideal environment for maintaining cell culture stocks. These early incubators were made up of bell jars that contained a single lit candle. Cultures were placed near the flame on the underside of the jar's lid, the entire jar was placed in a dry, heated oven. In the late 19th century, doctors realized another practical use for incubators: keeping premature or weak infants alive; the first infant incubator, used at a women's hospital in Paris, was heated by kerosene lamps. Fifty years Julius H. Hess, an American physician considered to be the father of neonatology, designed an electric infant incubator that resembles the infant incubators in use today; the next innovation in incubator technology came in the 1960s, when the CO2 incubator was introduced to the market. Demand came when doctors realized that they could use CO2 incubators to identify and study pathogens found in patients' bodily fluids. To do this, a sample was placed onto a sterile dish and into the incubator.
The air in the incubator was kept at 37 degrees Celsius, the same temperature as the human body, the incubator maintained the atmospheric carbon dioxide and nitrogen levels necessary to promote cell growth. At this time, incubators began to be used in genetic engineering. Scientists could create biologically essential proteins, such as insulin, with the use of incubators. Genetic modification could now take place on a molecular level, helping to improve the nutritional content and resistance to pestilence and disease of fruits and vegetables. Incubators serve a variety of functions in a scientific lab. Incubators maintain a constant temperature, however additional features are built in. Many incubators control humidity. Shaking incubators incorporate movement to mix cultures. Gas incubators regulate the internal gas composition; some incubators have a means of circulating the air inside of them to ensure distribution of temperatures. Many incubators built for laboratory use have a redundant power source, to ensure that power outages do not disrupt experiments.
Incubators are made in a variety of sizes, from tabletop models, to warm rooms, which serve as incubators for large numbers of samples. Egyptian egg oven
A glass stirring rod, glass rod, stirring rod or stir rod is a piece of laboratory equipment used to mix chemicals and liquids for laboratory purposes. They are made of solid glass, about the thickness and longer than a drinking straw, with rounded ends. Stir rods are made of borosilicate or polypropylene, they are between 10 and 40 centimeters in length and about half a centimeter thick. They are created from a single length of thin glass, cut into smaller segments; the ends are rounded by flame polishing to prevent scratching the surface of glassware during use, which may lead to cracks on when glassware are 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. While remarkably sturdy due to their construction, they can break and care should be taken when putting them under stress. A stirring rod is used for mixing liquid. Chemical reactions require agitation to proceed, the stir rod serves as a way for a scientist to provide controlled agitation without interacting with the chemicals directly.
Stir rods are used as part of proper laboratory technique when decanting supernatants because the contact helps to negate the adhesion between the side of the glassware and the supernatant, responsible for the liquid running down the side. Using a stir rod grants more control over the rate of flow, important in cases where chemicals may react violently; this process is used to pour a large-mouthed flask or beaker into a test tube. Glass rods can be used to induce crystallization in a recrystallization procedure, when they are used to scratch the inside surface of a test tube or beaker, they can break up an emulsion during an extraction. It is recommended. Glass rods can be cleaned by placing them in a beaker of clean water and stirring; these are two classic experiments performed using glass rods. This experiment introduces students to the concept of an index of refraction in a liquid. Glass rods are placed in this case oil and water. In water, the glass rods are visible because the refractive index of water is different for water and glass.
In the oil, the glass rods seem to disappear because they have a refractive index similar to that of glass, so the light doesn't bend as it crosses the glass/oil interface. Glass rods can be used to demonstrate electrification by friction; this occurs. In this instance, rubbing a glass rod with silk transfers negative charge from it; this effect can be performed with a variety of materials. Because glass rods and silk are common, they are chosen to demonstrate this effect. Magnetic stirrer Rubber policeman Swizzle stick
A heating mantle, or isomantle, is a piece of laboratory equipment used to apply heat to containers, as an alternative to other forms of heated bath. In contrast to other heating devices, such as hotplates or Bunsen burners, glassware containers may be placed in direct contact with the heating mantle without increasing the risk of the glassware shattering, because the heating element of a heating mantle is insulated from the container so as to prevent excessive temperature gradients. Heating mantles may have various forms. In a common arrangement, electric wires are embedded within a strip of fabric that can be wrapped around a flask; the current supplied to the device, hence the temperature achieved, is regulated by a rheostat. This type of heating mantle is quite useful for maintaining an intended temperature within a separatory funnel, for example, after the contents of a reaction have been removed from a primary heat source. Another variety of heating mantle may resemble a paint can and is constructed as a "basket" within a cylindrical canister.
The rigid metal exterior supports a "basket" made of fabric and includes heating elements within the body of the heating mantle. To heat an object, it is placed within the basket of the heating mantle. In further contrast to other methods of applying heat to a flask, such as an oil bath or water bath, using a heating mantle generates no liquid residue to drip off the flask. Heating mantles distribute heat evenly over the surface of the flask and exhibit less tendency to generate harmful hotspots. Heating element Laboratory equipment Wire gauze Double boiler
A kiln is a thermally insulated chamber, a type of oven, that produces temperatures sufficient to complete some process, such as hardening, drying, or chemical changes. Kilns have been used for millennia to turn objects made from clay into pottery and bricks. Various industries use rotary kilns for pyroprocessing—to calcinate ores, to calcinate limestone to lime for cement, to transform many other materials; the word kiln descends from the Old English cylene (/ˈkylene/, adapted from the Latin culīna "kitchen, cooking-stove, burning-place". During the Middle English Period, the "n" was not pronounced, as evidenced by kiln having been spelled without the "n", Another word, "miln", a place where wheat is ground had a silent "n". Whereas the spelling of "miln" was changed to "mill" to match its pronunciation, "kiln" maintained its spelling, which most led to a common mispronunciation, which has now become used. However, there are small bastions. Kiln, Mississippi, a small town known for its wood drying kilns that once served the timber industry, is still referred to as "the Kill" by locals.
Unwittingly adding the "n" sound at the end of "kiln" is due to people being introduced to the word through the written language before hearing the actual pronunciation. Linguists call this phenomenon "reading pronunciation" where an incorrect pronunciation is read aloud, becomes widespread reported by dictionaries, the "original pronunciation, passed from parent to child, mouth to ear, for many generations is lost."Phonetically, the "ln" in "kiln" is categorized as a digraph: a combination of two letters that make only one sound, such as the "mn" in "hymn". From English Words as Spoken and Written for Upper Grades by James A. Bowen 1900: "The digraph ln, n silent, occurs in kiln. A fall down the kiln can kill you." Bowen was pointing out the humorous fact. Pit fired pottery was produced for thousands of years before the earliest known kiln, which dates to around 6000 BC, was found at the Yarim Tepe site in modern Iraq. Neolithic kilns were able to produce temperatures greater than 900 °C. Uses include: Annealing and deforming glass, or fusing metallic oxide paints to the surface of glass Heat treatment for metallic workpieces Ceramics Brickworks Melting metal for casting Smelting ore to extract metal Pyrolysis of chemical materials Heating limestone with clay in the manufacture of Portland cement, the Cement kiln Heating limestone to make quicklime or calcium oxide, the Lime kiln Heating gypsum to make plaster of Paris For cremation Drying of tobacco leaves Drying malted barley for brewing and other fermentations Drying hops for brewing Drying corn before grinding or storage, sometimes called a corn kiln, corn drying kiln.
Drying green lumber so it can be used Drying wood for use as firewood Heating wood to the point of pyrolysis to produce charcoal Kilns are an essential part of the manufacture of all ceramics. Ceramics require high temperatures so chemical and physical reactions will occur to permanently alter the unfired body. In the case of pottery, clay materials are shaped and fired in a kiln; the final characteristics are determined by the composition and preparation of the clay body and the temperature at which it is fired. After a first firing, glazes may be used and the ware is fired a second time to fuse the glaze into the body. A third firing at a lower temperature may be required to fix overglaze decoration. Modern kilns have sophisticated electrical control systems to firing regime, although pyrometric devices are also used. Clay consists of fine-grained particles, that are weak and porous. Clay is combined with other minerals to create a workable clay body. Part of the firing process includes sintering.
This heats the clay until the particles melt and flow together, creating a strong, single mass, composed of a glassy phase interspersed with pores and crystalline material. Through firing, the pores are reduced in size; this crystalline material predominantly consists of aluminium oxides. In the broadest terms, there are two types of kiln: intermittent and continuous, both sharing the same basic characteristics of being an insulated box with a controlled inner temperature and atmosphere. A continuous kiln, sometimes called a tunnel kiln, is a long structure in which only the central portion is directly heated. From the cool entrance, ware is transported through the kiln, its temperature is increased as it approaches the central, hottest part of the kiln. From there, it continues through the kiln, the surrounding temperature is reduced until it exits the kiln nearly at room temperature. A continuous kiln is energy-efficient, because heat given off during cooling is recycled to pre-heat the incoming ware.
In some designs, the ware is left in one place. Kilns in this type include: Hoffmann kiln Bull’s Trench kiln Habla kiln Roller kiln: A special type of kiln, common in tableware and tile manufacture, is the roller-hearth kiln, in which wares placed on bats are carried through the kiln on rollers. In the intermittent kiln. the ware to be fired is placed into the kiln. The kiln is closed, the internal temperature increased according to a schedule. After the firing is completed, both the kiln and the ware are cooled; the ware is removed, the kiln is cleaned and the next cycle begins. Kilns in this type include: Clamp kiln Skove kiln Scotch kiln Down-Draft kiln Shuttle Kilns: this is a car-bottom kiln with a door