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Stopcock
A stopcock is a form of valve used to control the flow of a liquid or gas. The term is not precise and is applied to many different types of valve. The only consistent attribute is that the valve is designed to completely stop the flow when closed fully. Use Water service Stopcocks are used to grossly regulate the flow of tap water in residential and commercial services. One is found at the junction of a water main and the branch leading to an individual service (allowing the service to be isolated from the main trunk), and a second inside the structure (allowing its plumbing to be isolated from the branch line leading into it). Either is employed when maintenance or emergency repairs are conducted. Laboratory For laboratory glassware, items sometimes have plug valves with conically-tapered inserts called stopcocks (sometimes referred to as "plugs" by laypeople) with different bores. The valve bodies are usually made of glass, while the plugs are made of glass or Teflon. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Burette
A burette is a graduated glass tube with a tap at one end, for delivering known volumes of a liquid, especially in titrations. It is a long, graduated glass tube, with a stopcock at its lower end and a tapered capillary tube at the stopcock's outlet. The flow of liquid from the tube to the burette tip is controlled by the stopcock valve. There are two main types of burette; the volumetric burette and the piston burette. A volumetric burette delivers measured volumes of liquid. Piston burettes are similar to syringes, but with a precision bore and a plunger. Piston burettes may be manually operated or may be motorized. A weight burette delivers measured weights of a liquid. Overview A burette is a volumetric measuring glassware which is used in analytical chemistry for the accurate dispensing of a liquid, especially of one of the reagents in a titration. The burette tube carries graduated marks from which the dispensed volume of the liquid can be determined. Compared to a volumet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Burette
A burette is a graduated glass tube with a tap at one end, for delivering known volumes of a liquid, especially in titrations. It is a long, graduated glass tube, with a stopcock at its lower end and a tapered capillary tube at the stopcock's outlet. The flow of liquid from the tube to the burette tip is controlled by the stopcock valve. There are two main types of burette; the volumetric burette and the piston burette. A volumetric burette delivers measured volumes of liquid. Piston burettes are similar to syringes, but with a precision bore and a plunger. Piston burettes may be manually operated or may be motorized. A weight burette delivers measured weights of a liquid. Overview A burette is a volumetric measuring glassware which is used in analytical chemistry for the accurate dispensing of a liquid, especially of one of the reagents in a titration. The burette tube carries graduated marks from which the dispensed volume of the liquid can be determined. Compared to a volumet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plug Valve
Plug valves are valves with cylindrical or conically tapered "plugs" which can be rotated inside the valve body to control flow through the valve. The plugs in plug valves have one or more hollow passageways going sideways through the plug, so that fluid can flow through the plug when the valve is open. Plug valves are simple and often economical. When the plug is conically tapered, the stem/handle is typically attached to the larger diameter end of the plug. Plug valves usually do not have bonnets but often have the end of the plug with the handle exposed or mostly exposed to the outside. In such cases, there is usually not much of a stem. The stem and handle often come in one piece, often a simple, approximately L-shaped handle attached to the end of the plug. The other end of the plug is often exposed to the outside of the valve too, but with a mechanism that retains the plug in the body. The simplest and most common general type of plug valve is a 2-port valve with two positi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schlenk Line
The Schlenk line (also vacuum gas manifold) is a commonly used chemistry apparatus developed by Wilhelm Schlenk. It consists of a dual manifold with several ports. One manifold is connected to a source of purified inert gas, while the other is connected to a vacuum pump. The inert-gas line is vented through an oil bubbler, while solvent vapors and gaseous reaction products are prevented from contaminating the vacuum pump by a liquid-nitrogen or dry-ice/acetone cold trap. Special stopcocks or Teflon taps allow vacuum or inert gas to be selected without the need for placing the sample on a separate line. Schlenk lines are useful for safely and successfully manipulating moisture- and air-sensitive compounds. The vacuum is also often used to remove the last traces of solvent from a sample. Vacuum and gas manifolds often have many ports and lines, and with care, it is possible for several reactions or operations to be run simultaneously. When the reagents are highly susceptible t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schlenk Flask
A Schlenk flask, or Schlenk tube, is a reaction vessel typically used in air-sensitive chemistry, invented by Wilhelm Schlenk. It has a side arm fitted with a PTFE or ground glass stopcock, which allows the vessel to be evacuated or filled with gases (usually inert gases like nitrogen or argon). These flasks are often connected to Schlenk lines, which allow both operations to be done easily. Schlenk flasks and Schlenk tubes, like most laboratory glassware, are made from borosilicate glass such as Pyrex. Schlenk flasks are round-bottomed, while Schlenk tubes are elongated. They may be purchased off-the-shelf from laboratory suppliers or made from round-bottom flasks or glass tubing by a skilled glassblower. Evacuating a Schlenk flask Typically, before solvent or reagents are introduced into a Schlenk flask, the flask is dried and the atmosphere of the flask is exchanged with an inert gas. A common method of exchanging the atmosphere of the flask is to flush the flask out with an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laboratory Glassware
Laboratory glassware refers to a variety of equipment used in scientific work, and traditionally made of glass. Glass can be blown, bent, cut, molded, and formed into many sizes and shapes, and is therefore common in chemistry, biology, and analytical laboratories. Many laboratories have training programs to demonstrate how glassware is used and to alert first–time users to the safety hazards involved with using glassware. History Ancient era The history of glassware dates back to the Phoenicians who fused obsidian together in campfires making the first glassware. Glassware evolved as other ancient civilizations including the Syrians, Egyptians, and Romans refined the art of glassmaking. Mary the Jewess, an alchemist in Alexandria during the 1st century AD, is credited for the creation of some of the first glassware for chemical such as the ''kerotakis'' which was used for the collection of fumes from a heated material. Despite these creations, glassware for chemical u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laboratory Glassware
Laboratory glassware refers to a variety of equipment used in scientific work, and traditionally made of glass. Glass can be blown, bent, cut, molded, and formed into many sizes and shapes, and is therefore common in chemistry, biology, and analytical laboratories. Many laboratories have training programs to demonstrate how glassware is used and to alert first–time users to the safety hazards involved with using glassware. History Ancient era The history of glassware dates back to the Phoenicians who fused obsidian together in campfires making the first glassware. Glassware evolved as other ancient civilizations including the Syrians, Egyptians, and Romans refined the art of glassmaking. Mary the Jewess, an alchemist in Alexandria during the 1st century AD, is credited for the creation of some of the first glassware for chemical such as the ''kerotakis'' which was used for the collection of fumes from a heated material. Despite these creations, glassware for chemical u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Desiccator
Desiccators are sealable enclosures containing desiccants used for preserving moisture-sensitive items such as cobalt chloride paper for another use. A common use for desiccators is to protect chemicals which are hygroscopic or which react with water from humidity. The contents of desiccators are exposed to atmospheric moisture whenever the desiccators are opened. It also requires some time to achieve a low humidity. Hence they are not appropriate for storing chemicals which react quickly or violently with atmospheric moisture such as the alkali metals; a glovebox or Schlenk-type apparatus may be more suitable for these purposes. Desiccators are sometimes used to remove traces of water from an almost-dry sample. Where a desiccator alone is unsatisfactory, the sample may be dried at elevated temperature using Abderhalden's drying pistol. Constituents The lower compartment of the desiccator contains lumps of silica gel, freshly calcined quicklime, Drierite or (not as effectiv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Grease (lubricant)
Grease is a solid or semisolid lubricant formed as a dispersion of thickening agents in a liquid lubricant. Grease generally consists of a soap emulsified with mineral or vegetable oil. A common feature of greases is that they possess a high initial viscosity, which upon the application of shear, drops to give the effect of an oil-lubricated bearing of approximately the same viscosity as the base oil used in the grease. This change in viscosity is called shear thinning. Grease is sometimes used to describe lubricating materials that are simply soft solids or high viscosity liquids, but these materials do not exhibit the shear-thinning properties characteristic of the classical grease. For example, petroleum jellies such as Vaseline are not generally classified as greases. Greases are applied to mechanisms that can be lubricated only infrequently and where a lubricating oil would not stay in position. They also act as sealants to prevent ingress of water and incompressible mat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ramsay Grease
Ramsay grease is a vacuum grease, used as a lubrication and a sealant of ground glass joints and cocks on laboratory glassware, e.g. burettes. It is usable to about 10−2 mbar (about 1 Pa) and about 30 °C. Its vapor pressure at 20 °C is about 10−4 mbar (0.01 Pa). It is named after Sir William Ramsay. Different grades exist (e.g. thick or viscous, soft). The viscous one is used for standard stopcocks and ground joints. The soft grade is for large stopcocks and ground joints, desiccators, and for lower temperature use. Ramsay grease consists of paraffin wax, petroleum jelly, and crude natural rubber, in ratio 1:3:7 to 1:8:16. Due to the rubber content it has less tendency to flow. One recipe for a grease usable up to 25 °C consists of 6 parts of petroleum jelly, 1 part of paraffin wax, and 6 parts of Pará rubber. The dropping point of Leybold-brand Ramsay grease is 56 °C; its maximum service temperature is 25-30 °C. Its vapor pressure at 25 ° ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oil Bubbler
A gas bubbler is a piece of laboratory glassware which consists of a glass bulb filled with a small amount of fluid — usually mineral or silicone oil, less commonly mercury. The inlet to the bulb is connected to a ground glass joint, while the outlet is vented to the air. Gas bubblers are used to exclude air from a reaction or a system. In the former case, the gas bubbler is fitted on the condenser of the reaction set-up. In the latter case, an oil bubbler is usually installed at the end of the inert gas manifold on a Schlenk line to prevent contamination by atmospheric oxygen and water. A gas bubbler acts as a one-way valve — gases (hot air, evolved gases, solvent vapors) from the inlet will bubble through the fluid before being vented to the atmosphere. If there were an underpressure in the reaction vessel (such as when heat is removed, and the gases within contract), some fluid is sucked into a sump to equalize the pressure, instead of air. Wherever possible, s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boring (manufacturing)
In machining, boring is the process of enlarging a hole that has already been drilled (or cast) by means of a single-point cutting tool (or of a boring head containing several such tools), such as in boring a gun barrel or an engine cylinder. Boring is used to achieve greater accuracy of the diameter of a hole, and can be used to cut a tapered hole. Boring can be viewed as the internal-diameter counterpart to turning, which cuts external diameters. There are various types of boring. The boring bar may be supported on both ends (which only works if the existing hole is a through hole), or it may be supported at one end (which works for both, through holes and blind holes). Lineboring (line boring, line-boring) implies the former. Backboring (back boring, back-boring) is the process of reaching through an existing hole and then boring on the "back" side of the workpiece (relative to the machine headstock). Because of the limitations on tooling design imposed by the fa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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