Misplaced Pages

#726273

38-587: Aeroscope was a type of compressed air camera for making films, constructed by Polish inventor Kazimierz Prószyński in 1909 (French patent from 10 April 1909) and built in England since 1911, at first by Newman & Sinclair , and from 1912 by Cherry Kearton Limited. Patented in England in 1910 by the Polish inventor Kazimierz Prószyński , Aeroscope was the first successful hand-held operated film camera. It has been powered by compressed air pumped before filming into

76-455: A 600 kPa (87 psi) compressed air plant provided power to pneumatic drills , increasing productivity greatly over previous manual drilling methods. Compressed-air drills were applied at mines in the United States in the 1870s. George Westinghouse invented air brakes for trains starting in 1869; these brakes considerably improved the safety of rail operations. In the 19th century, Paris had

114-460: A function of partial pressure. Using diving terms, partial pressure is calculated as: For the component gas "i": For example, at 50 metres (164 ft) underwater, the total absolute pressure is 6 bar (600 kPa) (i.e., 1 bar of atmospheric pressure + 5 bar of water pressure) and the partial pressures of the main components of air , oxygen 21% by volume and nitrogen approximately 79% by volume are: The minimum safe lower limit for

152-424: A mixture of gases , each constituent gas has a partial pressure which is the notional pressure of that constituent gas as if it alone occupied the entire volume of the original mixture at the same temperature . The total pressure of an ideal gas mixture is the sum of the partial pressures of the gases in the mixture ( Dalton's Law ). The partial pressure of a gas is a measure of thermodynamic activity of

190-676: A particular gas in a mixture is the volume of one component of the gas mixture. It is useful in gas mixtures, e.g. air, to focus on one particular gas component, e.g. oxygen. It can be approximated both from partial pressure and molar fraction: V X = V t o t × p X p t o t = V t o t × n X n t o t {\displaystyle V_{\rm {X}}=V_{\rm {tot}}\times {\frac {p_{\rm {X}}}{p_{\rm {tot}}}}=V_{\rm {tot}}\times {\frac {n_{\rm {X}}}{n_{\rm {tot}}}}} Vapor pressure

228-455: A per unit energy delivered basis. Compressed air is used for many purposes, including: Compressor rooms must be designed with ventilation systems to remove waste heat produced by the compressors. When air at atmospheric pressure is compressed, it contains much more water vapor than the high-pressure air can hold. Relative humidity is governed by the properties of water and is not affected by air pressure. After compressed air cools, then

266-396: A reversible reaction involving gas reactants and gas products, such as: a A + b B ↽ − − ⇀ c C + d D {\displaystyle {\ce {{{\mathit {a}}A}+{{\mathit {b}}B}<=>{{\mathit {c}}C}+{{\mathit {d}}D}}}}

304-458: A risk when these oxygen partial pressures and exposures are exceeded. The partial pressure of oxygen also determines the maximum operating depth of a gas mixture. Narcosis is a problem when breathing gases at high pressure. Typically, the maximum total partial pressure of narcotic gases used when planning for technical diving may be around 4.5 bar absolute, based on an equivalent narcotic depth of 35 metres (115 ft). The effect of

342-544: A slope, to prevent accumulation of moisture in low parts of the piping system. Drain valves may be installed at multiple points of a large system to allow trapped water to be blown out. Taps from piping headers may be arranged at the tops of pipes, so that moisture is not carried over into piping branches feeding equipment. Piping sizes are selected to avoid excessive energy loss in the piping system due to excess velocity in straight pipes at times of peak demand, or due to turbulence at pipe fittings. Partial pressure In

380-952: A system of pipes installed for municipal distribution of compressed air to power machines and to operate generators for lighting. Early air compressors were steam-driven, but in certain locations a trompe could directly obtain compressed air from the force of falling water. Air for breathing may be stored at high pressure and gradually released when needed, as in scuba diving , or produced continuously to meet requirements, as in surface-supplied diving . Air for breathing must be free of oil and other contaminants; carbon monoxide, for example, in trace volumetric fractions that might not be dangerous at normal atmospheric pressure may have deadly effects when breathing pressurized air due to proportionally higher partial pressure . Air compressors, filters, and supply systems intended for breathing air are not generally also used for pneumatic tools or other purposes, as air quality requirements differ. Workers constructing

418-461: A toxic contaminant such as carbon monoxide in breathing gas is also related to the partial pressure when breathed. A mixture which may be relatively safe at the surface could be dangerously toxic at the maximum depth of a dive, or a tolerable level of carbon dioxide in the breathing loop of a diving rebreather may become intolerable within seconds during descent when the partial pressure rapidly increases, and could lead to panic or incapacitation of

SECTION 10

#1732855845727

456-400: Is a hazard when diving. For diving much beyond 30 metres (100 ft), it is less safe to use air alone and special breathing mixes containing helium are often used. In industry, compressed air is so widely used that it is often regarded as the fourth utility, after electricity, natural gas and water. However, compressed air is more expensive than the other three utilities when evaluated on

494-455: Is often called the normal boiling point . The higher the vapor pressure of a liquid at a given temperature, the lower the normal boiling point of the liquid. The vapor pressure chart displayed has graphs of the vapor pressures versus temperatures for a variety of liquids. As can be seen in the chart, the liquids with the highest vapor pressures have the lowest normal boiling points. For example, at any given temperature, methyl chloride has

532-496: Is quite often referred to as the Henry's law constant. Henry's law is sometimes written as: where k ′ {\displaystyle k'} is also referred to as the Henry's law constant. As can be seen by comparing equations ( 1 ) and ( 2 ) above, k ′ {\displaystyle k'} is the reciprocal of k {\displaystyle k} . Since both may be referred to as

570-431: Is the pressure of a vapor in equilibrium with its non-vapor phases (i.e., liquid or solid). Most often the term is used to describe a liquid 's tendency to evaporate . It is a measure of the tendency of molecules and atoms to escape from a liquid or a solid . A liquid's atmospheric pressure boiling point corresponds to the temperature at which its vapor pressure is equal to the surrounding atmospheric pressure and it

608-533: Is to produce compressed air—amounting to 80 terawatt hours consumption per year. Industrial use of piped compressed air for power transmission was developed in the mid-19th century; unlike steam , compressed air could be piped for long distances without losing pressure due to condensation. An early major application of compressed air was in the drilling of the Mont Cenis Tunnel in Italy and France in 1861, where

646-515: Is true across a very wide range of different concentrations of oxygen present in various inhaled breathing gases or dissolved in blood; consequently, mixture ratios, like that of breathable 20% oxygen and 80% Nitrogen, are determined by volume instead of by weight or mass. Furthermore, the partial pressures of oxygen and carbon dioxide are important parameters in tests of arterial blood gases . That said, these pressures can also be measured in, for example, cerebrospinal fluid . The symbol for pressure

684-429: Is usually p or pp which may use a subscript to identify the pressure, and gas species are also referred to by subscript. When combined, these subscripts are applied recursively. Examples: Dalton's law expresses the fact that the total pressure of a mixture of ideal gases is equal to the sum of the partial pressures of the individual gases in the mixture. This equality arises from the fact that in an ideal gas,

722-409: The equilibrium so as to favor either the right or left side of the reaction in accordance with Le Chatelier's Principle . However, the reaction kinetics may either oppose or enhance the equilibrium shift. In some cases, the reaction kinetics may be the overriding factor to consider. Gases will dissolve in liquids to an extent that is determined by the equilibrium between the undissolved gas and

760-435: The Henry's law constant, readers of the technical literature must be quite careful to note which version of the Henry's law equation is being used. Henry's law is an approximation that only applies for dilute, ideal solutions and for solutions where the liquid solvent does not react chemically with the gas being dissolved. In underwater diving the physiological effects of individual component gases of breathing gases are

798-687: The camera with a simple hand pump, similar to the one we still use to pump bicycle tyres . Filming with Aeroscope, a cameraman did not have to turn the crank to advance the material filming, as in all cameras of that time, so he could operate the camera with both hands, holding the camera and controlling the focus. This made it possible to film with the Aeroscope hand-held in most difficult circumstances, as well as made possible to film from airplanes , also for military purposes. Camera carried 400 feet (120 m) of 35mm film and, once pressurised, could work with no further pumping for up to 10 minutes. The Aeroscope

SECTION 20

#1732855845727

836-517: The disease on projects such as the Brooklyn Bridge and the Eads Bridge and it was not until the 1890s that it was understood that workers had to decompress slowly, to prevent the formation of dangerous bubbles in tissues. Air under moderately high pressure, such as is used when diving below about 20 metres (70 ft), has an increasing narcotic effect on the nervous system. Nitrogen narcosis

874-422: The equilibrium constant of the reaction would be: K p = p C c p D d p A a p B b {\displaystyle K_{\mathrm {p} }={\frac {p_{C}^{c}\,p_{D}^{d}}{p_{A}^{a}\,p_{B}^{b}}}} For reversible reactions, changes in the total pressure, temperature or reactant concentrations will shift

912-401: The following isotherm relation: V X V t o t = p X p t o t = n X n t o t {\displaystyle {\frac {V_{\rm {X}}}{V_{\rm {tot}}}}={\frac {p_{\rm {X}}}{p_{\rm {tot}}}}={\frac {n_{\rm {X}}}{n_{\rm {tot}}}}} The partial volume of

950-469: The foundations of bridges or other structures may be working in a pressurized enclosure called a caisson , where water is prevented from entering the open bottom of the enclosure by filling it with air under pressure. It was known as early as the 17th century that workers in diving bells experienced shortness of breath and risked asphyxia, relieved by the release of fresh air into the bell. Such workers also experienced pain and other symptoms when returning to

988-417: The gas that has dissolved in the liquid (called the solvent ). The equilibrium constant for that equilibrium is: where: The form of the equilibrium constant shows that the concentration of a solute gas in a solution is directly proportional to the partial pressure of that gas above the solution . This statement is known as Henry's law and the equilibrium constant k {\displaystyle k}

1026-403: The gas's molecules . Gases dissolve, diffuse, and react according to their partial pressures but not according to their concentrations in gas mixtures or liquids. This general property of gases is also true in chemical reactions of gases in biology. For example, the necessary amount of oxygen for human respiration, and the amount that is toxic, is set by the partial pressure of oxygen alone. This

1064-415: The highest vapor pressure of any of the liquids in the chart. It also has the lowest normal boiling point (−24.2 °C), which is where the vapor pressure curve of methyl chloride (the blue line) intersects the horizontal pressure line of one atmosphere ( atm ) of absolute vapor pressure. At higher altitudes, the atmospheric pressure is less than that at sea level, so boiling points of liquids are reduced. At

1102-594: The improved Aeroscope cameras were in use by the British combat cameramen. Compressed air Compressed air is used as a breathing gas by underwater divers . It may be carried by the diver in a high-pressure diving cylinder , or supplied from the surface at lower pressure through an air line or diver's umbilical . Similar arrangements are used in breathing apparatus used by firefighters, mine rescue workers and industrial workers in hazardous atmospheres. In Europe, 10 percent of all industrial electricity consumption

1140-493: The molecules are so far apart that they do not interact with each other. Most actual real-world gases come very close to this ideal. For example, given an ideal gas mixture of nitrogen (N 2 ), hydrogen (H 2 ) and ammonia (NH 3 ): p = p N 2 + p H 2 + p NH 3 {\displaystyle p=p_{{\ce {N2}}}+p_{{\ce {H2}}}+p_{{\ce {NH3}}}} where: Ideally

1178-424: The partial pressure of an individual gas component in an ideal gas can be obtained using this expression: p i = x i ⋅ p {\displaystyle p_{\mathrm {i} }=x_{\mathrm {i} }\cdot p} The mole fraction of a gas component in a gas mixture is equal to the volumetric fraction of that component in a gas mixture. The ratio of partial pressures relies on

Aeroscope - Misplaced Pages Continue

1216-602: The partial pressures of oxygen in a breathing gas mixture for diving is 0.16 bars (16 kPa) absolute. Hypoxia and sudden unconsciousness can become a problem with an oxygen partial pressure of less than 0.16 bar absolute. Oxygen toxicity , involving convulsions, becomes a problem when oxygen partial pressure is too high. The NOAA Diving Manual recommends a maximum single exposure of 45 minutes at 1.6 bar absolute, of 120 minutes at 1.5 bar absolute, of 150 minutes at 1.4 bar absolute, of 180 minutes at 1.3 bar absolute and of 210 minutes at 1.2 bar absolute. Oxygen toxicity becomes

1254-559: The ratio of partial pressures equals the ratio of the number of molecules. That is, the mole fraction x i {\displaystyle x_{\mathrm {i} }} of an individual gas component in an ideal gas mixture can be expressed in terms of the component's partial pressure or the moles of the component: x i = p i p = n i n {\displaystyle x_{\mathrm {i} }={\frac {p_{\mathrm {i} }}{p}}={\frac {n_{\mathrm {i} }}{n}}} and

1292-469: The surface, as the pressure was relieved. Denis Papin suggested in 1691 that the working time in a diving bell could be extended if fresh air from the surface was continually forced under pressure into the bell. By the 19th century, caissons were regularly used in civil construction, but workers experienced serious, sometimes fatal, symptoms on returning to the surface, a syndrome called caisson disease or decompression sickness . Many workers were killed by

1330-413: The top of Mount Everest , the atmospheric pressure is approximately 0.333 atm, so by using the graph, the boiling point of diethyl ether would be approximately 7.5 °C versus 34.6 °C at sea level (1 atm). It is possible to work out the equilibrium constant for a chemical reaction involving a mixture of gases given the partial pressure of each gas and the overall reaction formula. For

1368-437: The vaporized water turns to liquefied water. Cooling the air as it leaves the compressor will take most of the moisture out before it gets into the piping. Aftercooler, storage tanks, etc. can help the compressed air cool to 104 °F; two-thirds of the water then turns to liquid. Management of the excessive moisture is a requirement of a compressed air distribution system. System designers must ensure that piping maintains

1406-449: The war cinematographers” who used it at the battle of the Somme. As several of the cameramen died filming from the firing lines Aeroscope got a name of camera of death . In 1928 Prószyński built an improved version of his camera, with an air pressure meter, but the more practical spring cameras like Eyemo and later Bolex took over. However, even by the beginning of World War II , some of

1444-460: Was known for its simplicity and reliability. Hundreds of light and relatively compact Aeroscope cameras were used by the British War Office for the combat cameramen on the battlefields of World War I , and by all newsreel cameramen all over world, until the late 1920s. Aeroscope has been used among others by Arthur Herbert Malins recognized by Kelly (1997, Page 60) as “the most famous of

#726273