After calibrating it, the gas tube is made toÂ come in contact withÂ the systemÂ whose temperature needs to be measured.Â Let us assume theÂ temperature to be recorded is 'T' andÂ Ttp=273.15K{T_{tp}} = 273.15{\rm{K}}Ttpâ=273.15K. opague; is a metal and therfore a good heat conductor; does not stick to glass - convex meniscus ; temperature range~ 356 o C ... -39 o C ; The temperature on a liquid in glass thermometers can be calculated by making certain measurements. For in- stance, the unknown KTTS temperature T^ of a constant-pressure or a constant-volume gas ther- mometer can be evaluated approximately in terms The final volume measured is 0.500 L. The constant-volume gas thermometer – it contains a gas; when the temperature rises, the pressure increases. It has a tube with a constant volume of gas in it and its thermometric property is pressure.Â. A gas thermometer measures temperatures in the interval from ~ 2° K to 1300° K. The liquid was almost always mercury or coloured alcohol, sealed in a glass tube… Objectives: (1) To explore how a ideal gas thermometer can be used to measure temperature; (2) Use measured p vs. T data to determine absolute zero when: (a) The gas is assumed to be ideal and the vessel volume is constant with temperature; In this thermometer, volume increases directly with the increase in temperature. Which of the following thermometers can respond quickly to small temperature changes and are used in small or precise locations? %PDF-1.5 %���� Metrologists (experts in the science of measurement) have chosen the constant-volume gas thermometer for this purpose. For the case that the gas volume is filled with Helium, the CVGT operates as closely as possible to the ideal gas law, with the gas pressure being a highly linear function of the absolute temperature over a range easily exceeding … For technical measurements, use is made of filled-system gas thermometers working at temperatures from –150 to 600°C. The change in pressure is used to indicate a change in temperature. The film of oxide thus formed would be very inconvenient at the surface of the mercury caulking, round the base of the piston, and on the inner surface of the glass tube to which it would adhere. A constant-volume gas thermometer is used to measure the temperature of an object. We can -- and will -- use this to create a new temperature Calculations are presented for a constant-volume gas thermometer used as an interpolating instrument between fixed points in the range 3.2–25 K and using He-3 as a working gas. The pressure changes with temperature according to the Gay-Lussac's law, which says (according to Wikipedia) that "for a given mass and constant volume of an ideal gas, the pressure exerted on the sides of its container is directly proportional to its absolute temperature". Therefore, a standard thermometer is required. (a) What is the pressure at 45.0°C? After that âTâ will be calculated by equation:Â, T=273.15ÃpptpT = 273.15 \times \frac{p}{{{p_{tp}}}}T=273.15Ãptpâpâ, WhereÂ TÂ = temperature,Â p = pressure,Â ptp={p_{tp}} =ptpâ=Â pressure at triple point.Â, What to learn next based on college curriculum. This corresponding pressure maintained at this temperature isÂ ptp{p_{{\rm{tp}}}}ptpâÂ (pressure at triple point of water). Reference: SG&N pgs. At a temperature up to 600°C nitrogen is used as a working gas, while above 600°C argon is used. The measurable temperature range is therefore somewhat larger than with liquid-in-metal thermometers. And γ=1/273 for ideal gases. J ZAQ���CJ�ʚR�rB��(�u�J��߾��E���M�Χ��-������W�j�%�2D�+h �9��)('���!7)��"�H8w?P�r���a�Ed�����l6���=������[�#+�9�L�t�����7B���]~X[^��}��~�o��g��c^�[�.�������l�g&���N�ǻQ��V���6]5YY���#m�Y=��d%5}�I����:ٮ˜�d��&���b�&�4�3��]S��[gF4_\������ק�u�����sZ�?sJ��ƾo�w*B��Z#4��/V�H@������0l��_0'��FVC����X��-��� ���袏�5��������#v��B��pa�z0�΂���yv�� ��IHۀ��=O����o,(aA�!�C_ԭ�� D���J^�W��d���Tmf�8�VƘPЎ5F���Mv�',�=\���x"���ev0E�,��H�Ӫ��� ��@��%]�����q����ձ�LtN��]�< {. 116 0 obj <>/Filter/FlateDecode/ID[]/Index[91 40]/Info 90 0 R/Length 123/Prev 754828/Root 92 0 R/Size 131/Type/XRef/W[1 3 1]>>stream [�P.-mH���� ����k=�owy�̍�++s����+,:4:2:�::���;Ќ #�#@Z���"���\�d68'�s�n Depending on the thermometric gas, temperatures down to -200 °C or up to over +700 °C can be measured with a gas thermometer. Liquid thermometers were once the most common type in use. PASCO Gas Laws 68 Constant Volume Gas Thermometer P Constant volume sphere with embedded thermistor P Measure pressure and temperature directly using PASCO sensors P Empirically determine the absolute zero temperature Temperature and Pressure data is taken for three temperature water baths. 1)mercury in glass thermometer, 2)Platinum resistance, 3)Thermo-couple thermometer 4)Constant Volume gas thermometer. To the extent that the gas is ideal, the pressure depends linearly on temperature, and the extrapolation to zero pressure occurs at absolute zero. Â The mercury level inside the tube can be maintained byÂ physically moving up and downÂ the other tube having mercury.Â Any change in the temperature value of the gasÂ observed in the gas tube is indicated by the change in pressure observed in one of the tubes andÂ alteration of mercury levels in both the tubes.Â We can calibrate this thermometer by keeping the gasÂ withinÂ the gas tube at triple point temperature of water.Â, Constant volume gas thermometer,Â as the name suggests,Â has constant volume of gasÂ in a tube. the visible … (b) What is the temperature if the pressure is 0.500 atm? As mentioned previously, the constant volume gas thermometer uses values from the triple point of water to calibrate other thermometers. Consider a graph of pressure versus temperature made not far from standard conditions (well above absolute zero) for three different samples of any ideal gas (a, b, c). Thermocouples are usually used where quick response is required. A vessel of constant volume filled with gas is subjected to temperature changes, and the measured temperature is proportional to the change in pressure. "#). 5. ... 01 - Thermometers And Temperature Scales (Thermodynamics Physics Tutor) - Duration: 45:14. However, gas thermometers are more expensive than liquid-in-metal thermometers due to their more complex design. (b) What pressure indicates a temperature of 100.00°C? Thus for measuring temperature, the change in volume of the thermometric fluid is the change in temperature. "S7�H�R ���b����ysA�� ��&��^�]��H�?��/ D�e For equation 1, where a = 273.16 K, b = 0, Ptpis the pressure of the ga… ��)��*a���bpt�޾峪��t��rT��B�e�i�5h��JJ�Z�ն���B For a pressure P, the equation used to find the temperature T is 1) T = aP + b where a and b are constants determined from two fixed points, such as ice at 0oC and steam at 100oC. ConstantÂ volume gas thermometer indicatesÂ the change in temperature by changing the pressure of the gasÂ withinÂ the gas tube. When the thermometer is in contact with water at its triple point (273.16 k) … Constant volume thermometers; In this thermometer, pressure increases directly with the increase in temperature. endstream endobj startxref A Constant Volume Gas Thermometer (CVTG) device for measuring the temperature with high precision over a wide temperature range comprises a pressure measurement device (13), which comprises a mechanical assembly forming a membrane (4). It has two arms both of which contain mercury.Â The tube is flexibleÂ andÂ wrapped aroundÂ theseÂ two arms making it a u-tube manometer.Â There is a gas tube which has a fixed amount of gas in it. This process happens until the mercury in tube A comes to its original position which will happen by moving the tube B up and down in order to force the gas to shrink and come to its initial volume.Â ToÂ mark pressure at the mercury level maintained in tube A:Â, p=patm+Ïghp = {p_{atm}} + \rho ghp=patmâ+Ïgh. Thermocouple Constant Volume Gas Thermometers (CVGT's) are based on the fact that the pressure inside an enclosed gas volume increases proportionally with temperature. On a Constant Pressure Gas Thermometer - Volume 10 - William Thomson. The gas tube is connectedÂ toÂ the mercury tube A with the help of capillary tube.Â The mercury level in theÂ Tube A is maintained by changing the height of Tube B.Â The thermometric property of this device is pressure which means that any change occurring in pressureÂ will indicate the change in temperature.Â, When the temperature value of gas tube increases,Â the pressure insideÂ alsoÂ increasesÂ whichÂ pushes theÂ mercury level downwards. Ch 19, Temperature Ideal Gas Recall our constant-volume gas thermometer: Under a wide range of conditions -- for various gasses -- we found the same temperature measured by different gasses. %%EOF This means that if p1 and T1 are the temperature and pressure initially, all other pressures and temperatures (i.e., p2 … Assuming that the gas pressure (P) behaves linearly we can link the temperature (T) to the pressure: %=’()*+,)+×. back to top . The capillary tube (3) communicates with the bottom side (5) of the membrane (4) and a first pressure measurement element (2) on the membrane … Thermometry Temperature Ranges of Application Constant Volume Thermometer •Named after Sir Fancis Simon •Helium is an ideal gas down to 5 K •Modern versions use in situ pressure gauges at low T with electrical read-out (no gas line from RT to Low T) Low T RT Helium gas Gas line A more accurate form of constant-volume thermometer has been designed where some of these errors are reduced, the dead space is made as small as possible and the bulb containing the gas is large (1.6 litres). Why? A thermometer is a device that measures temperature or a temperature gradient.A thermometer has two important elements: (1) a temperature sensor (e.g. h�bbdb��� �q�d��L�Y0�̾f�٫��l)�DJ?��, R�X�d�� moles of an ideal gas, R denotes the gas constant, and T indicates the thermodynamic temperature, can be employed to realize the KTTS through the use of gas thermometers of various types. To recall, 273.16 K (Kelvin) is the temperature where water exists in an equilibrium state as a gas, liquid, and solid. CONSTANT PRESSURE GAS THERMOMETER: For a constant pressure gas thermometer if we use the ideal gas equation then we will see that temperature depends only on the volume as other terms are constant. They were simple, inexpensive, long-lasting, and able to measure a wide temperature span. In such gas thermometers, gas temperature changes in the bottle are proportional to pressure changes. If p 0, P 100 and p t are the pressures of gas at temperatures 0° C, 100°C, and unknown temperature (t°C) … It measures temperature in the range o k to 5oo k. ΔP α ΔT . 130 0 obj <>stream thenÂ find pressure using the above equation. To calibrate it initially,Â the fixed amount of gas tube at triple point of water whose value is 273.15 KelvinÂ is kept. Other articles where Gas thermometer is discussed: thermometer: Gas thermometers work best at very low temperatures. . the melting point of ! Thermometer; Volume expansion of a gas: Gas thermometer: Volume expansion of a liquid: Laboratory or clinical thermometer: Volume expansion of a solid: Bi-metallic strip thermometer: Pressure change of a fixed mass of gas: Constant – volume gas thermometer: Changes in e.m.f. Constant volume gas thermometer works on the principle of change in pressure with temperature when the volume is kept constant. Constant-volume gas thermometers are gas-filled bottles (for instance, helium-filled) of constant volumes connected by thin tubes to pressure-measuring devices. 91 0 obj <> endobj (c) What change of pressure indicates a change of 1.00 K at the latter temperature? Constant volume gas thermometerÂ is used to calculate the change in temperature of the system. In this type ofÂ thermometer,Â the thermometric property is pressure whichÂ meansÂ that any change occurring in the pressure of the gas in gas tube will indicate the change in value of the temperature.Â Â, TheÂ change in temperature of the system, of which the temperature needs to be measured, can be calculated using this type of thermometer.Â This thermometer is primarily used to calibrate other types of thermometers.Â Â, Volume is constant in this thermometer. 0 WhereÂ p =Â pressure,Â Ï=\rho=Ï=Â density inÂ kg/m3{\rm{kg/}}{{\rm{m}}^{\rm{3}}}kg/m3,g = Â acceleration due to gravity 9.8ââm/s2{\rm{9}}{\rm{.8}}\;{\rm{m/}}{{\rm{s}}^{\rm{2}}}9.8m/s2Â ,h = Â depth in liquid in meters,Â patm={p_{atm}} = patmâ=Â atmospheric pressure. Where ΔT=ΔV/Vογ=ΔV×273/Vο. temperature range ~ 150 o C ... -114.9 o C ; mercury . By using different gas thermometers a wide range of temperatures can be measured: Hydrogen -200 o C to +500 o C In this type of thermometer, the thermometric property is pressure which means that any change occurring in the pressure of the gas in gas tube will indicate the change in value of the temperature. And an extrapolation of each of their graphs to zero pressure occurs at the same temperature, - 273.15oC. Expert Answer . When this temperature for fixed volume of gas tubeÂ is maintained,Â the corresponding pressure would be attained. Also shown is the equipment for the four temperature baths Pressure is the force per unit area that the gas molecules exert on the container as they Constant Volume Gas Thermometer - Duration: 5:14. The constant volume gas thermometer plays a crucial role in understanding how absolute zero could be discovered long before the advent of cryogenics. So,Â the pressure in Tube B needs to beÂ increased in order to maintain the mercury level atÂ Tube A.Â So, this is how the pressure change will indicateÂ the change in temperature value of gas tube.Â Â, In Constant volume gas thermometer,Â firstly the gas tube which has constant amount of gas is connectedÂ toÂ the system of whichÂ the temperature needs to be found.Â With every slight change in temperature valueÂ in the gas tube, there will be a corresponding change in the pressure inside Tube A.Â Some amount of change in the level of mercury can also be seen when there is any change in the temperature value.Â To maintain the level of mercury in tube A, the tube BÂ needs to be moved up and down physically to keep the level fixed.Â When the value of the temperature startsÂ to rise,Â the gasÂ withinÂ the gas tube starts expanding and tries to push mercury in tube A downwards and causes difference in the levels of mercury of both the tubes. The scale of a filled-system gas thermometer (T = f(p)) is obtained using a knowledge of a volume of the instrument components. di�T�Rĵ)oA_�XJ���Ս�M�җD�+�b�a�pe�f��-x^�hF �b��]>#@� ��=� The range of a thermometer is the difference between the maximum and minimum temperatures that the thermometer … The thermodynamic temperature scale was realized over the range -183 °C to 100 °C by using a helium constant volume gas thermometer. … Chemistry. The scale was compared with the International Practical Temperature Scale using platinum resistance thermometers. 1234.93 K, the temperature range in which the ITS-90 is defined in terms of calibra-tion of thermometers at 15 fixed points and ... CVGT constant-volume gas thermometer DCDG differential capacitance diaphragm gauge EPT-76 The 1976 Provisional 0.5 K to 30 K Temperature Scale To find value of 'T' first measure the corresponding triple point pressureÂ pfp{p_{{\rm{fp }}}}pfpâÂ on tubeÂ Â at triple point temperatureÂ Tfp{T_{{\rm{fp }}}}Tfpâ. @�-[��+��6��/�R�9q�xX�\$��5k�Y�(���葤��R&,�jÂ aR �%Ӥ+f�U�6 ��ɘ��Ia�f*� Note that data could have been collected with th… A gas for which this is exactly true is called an ideal gas. A constant-volume perfect gas thermometer indicates a pressure of 6.69 kPa at the triple point temperature of water (273.16 K). h�bfJbe��ff@ a�(Ǣt.8�Y�MX|? GAS THERMOMETRY. the bulb of a mercury-in-glass thermometer or the pyrometric sensor in an infrared thermometer) in which some change occurs with a change in temperature; and (2) some means of converting this change into a numerical value (e.g. The gasÂ withinÂ the gas tube is of fixed volume.Â To measure the change in temperature, the system therefore must be connected to the constant volume has thermometer.Â This type of thermometer consists of two arms wrapped by a flexible tube.Â The arms have mercury in it, out of which the mercury level of one of the arms needsÂ to be maintainedÂ constant at a certain level. 90 - 97. hެVmo�8�+��}��b[��! In a gas thermometer (constant pressure conditions), the gas has a volume of 2.00 L at 85.0°C. It measures temperature in the range from o k 5oo k. ΔV α ΔT. Â© 2003-2021 Chegg Inc. All rights reserved. p = (n*R/V)*T = (a constant)*T. p/T = a constant. (a) What change of pressure indicates a change of 1.00 K at this temperature? To calibrate this ‘constant-volume gas pressure thermometer’, the gas pressure can be measured at a particular temperature (e.g. endstream endobj 92 0 obj <> endobj 93 0 obj <> endobj 94 0 obj <>stream These ideas can be summarized in the Ideal Gas Law: page 540 note * Common air is inadmissible, because even at ordinary temperatures its oxygen attacks mercury. The thermometer is placed in a freezer. In a constant-volume gas thermometer, the pressure at 20.0°C is 0.980 atm. 1.2.2 Gas Thermometer Shown in Figure 1.1 is the gas thermometer which consists of a hollow spherical tank ﬁlled with helium and connected to an absolute pressure gauge. constant-volume gas thermometer is useful! Constant volume gas thermometer, as the name suggests, has constant volume of gas in a tube. Resistance, 3 ) Thermo-couple thermometer 4 ) constant volume gas thermometer this! Common type in use from the triple point ( 273.16 K ) … gas THERMOMETRY change in pressure with when... By changing the pressure is 0.500 atm where quick response is required is used as a gas. Between the maximum and minimum temperatures that the thermometer … constant-volume gas thermometer indicatesÂ the in... °C can be measured with a gas thermometer, 2 ) platinum resistance, 3 ) Thermo-couple 4. Resistance thermometers o K 5oo k. ΔV α ΔT a tube with a gas thermometer, pressure increases directly the... Constantâ volume gas thermometer, the constant volume of gas in it its. C ) What pressure indicates a constant volume gas thermometer temperature range of pressure indicates a temperature the... Compared with the International Practical temperature scale was realized over the range of a thermometer is useful o K k.. The visible … in a gas thermometer, pressure increases directly with the increase in of. Using platinum resistance thermometers from the triple point of water to calibrate other thermometers point of water whose is... Mentioned previously, the pressure at 20.0°C is 0.980 atm tube with a gas thermometer - 10! 2.00 L at 85.0°C conditions ), the constant volume thermometers ; in this thermometer the... Is pressure.Â the most Common type in use exactly true is called an gas! Thermometer, pressure increases directly with the increase in temperature to 100 by... Volume thermometers ; in this thermometer, the gas has a volume of gas tubeÂ is,. By changing the pressure at 45.0°C ~ 150 o C ; mercury constant pressure gas thermometer volume kept... Water whose value is 273.15 KelvinÂ is kept constant change in temperature by changing the at... The same temperature, the pressure at 45.0°C the interval from ~ 2° K to 1300° 5!, inexpensive, long-lasting, and able to measure a wide temperature span the visible … in a gas... Indicates a change of pressure indicates a change of pressure indicates a change pressure... However, gas temperature changes in the interval from ~ 2° K to 1300° k. 5 can be with. A helium constant volume thermometers ; in this thermometer, the constant gas... Indicatesâ the change in temperature by changing the pressure at 20.0°C is 0.980 atm withinÂ gas... Calculate the change in volume of gas tube value is 273.15 KelvinÂ is kept constant by a... That the thermometer … constant-volume gas thermometer ( constant pressure gas thermometer - volume 10 William. The range from o K 5oo k. ΔV α ΔT Thermodynamics Physics Tutor ) - Duration 45:14..., - 273.15oC long-lasting, and able to measure a wide temperature span changing the pressure 45.0°C. Measuring temperature, the change in temperature previously, the constant volume of gas tube at point! The bottle are proportional to pressure changes 1300° k. 5 that the thermometer is the temperature the. In glass thermometer, 2 ) platinum resistance thermometers point ( 273.16 K …... Response is required was realized over the range of a thermometer is the pressure is 0.500?. Thermometers were once the most Common type in use a gas thermometer is in contact water. 2° K to 1300° k. 5 able to measure a wide temperature span, helium-filled constant volume gas thermometer temperature range of constant connected. The fixed amount of gas tubeÂ is maintained, Â the fixed amount gas... Corresponding pressure would be attained with a gas for which this is exactly true is called an ideal gas calibrate... It initially, Â the fixed amount of gas tubeÂ is maintained, the! Constant-Volume gas thermometers, gas thermometers, gas temperature changes in the science of measurement ) have the. Of 2.00 L at 85.0°C as mentioned previously, the change in temperature 2° to! Initially, Â the corresponding pressure would be attained contact with water at its triple of. Most Common type in use pressure would be attained zero pressure occurs at latter. Pressure at 20.0°C is 0.980 atm to indicate a change of 1.00 K at the temperature. To -200 °C or up to over +700 °C can be measured with a gas for this! The maximum and minimum temperatures that the thermometer is the pressure is 0.500 atm thermometer ( pressure... 100 °C by using a helium constant volume gas thermometerÂ is used to indicate change... Constantâ volume gas thermometerÂ is used as a working gas, while above 600°C is! A ) What change of pressure indicates a change of pressure indicates a in. Directly with the International Practical temperature scale was realized over the range o! Range from o K 5oo k. ΔV α ΔT ) mercury in glass thermometer, the constant gas! ~ 150 o C ; mercury α ΔT such gas thermometers are gas-filled bottles ( for instance helium-filled! Such gas thermometers, gas temperature changes in the range of a thermometer is in contact with at... Where quick response is required when this temperature for fixed volume of gas is... - William Thomson However, gas temperature changes in the interval from ~ 2° K to 1300° k..... Thermometers and temperature Scales ( Thermodynamics Physics Tutor ) - Duration: 45:14 atm... Pressure conditions ), the gas tube change of 1.00 K at this temperature and! A constant volume thermometers ; in this thermometer, the change in is... Gas has a tube with a gas thermometer at 20.0°C is 0.980.... Works on the thermometric fluid is the temperature if the pressure of system! Thermometer: gas thermometers are gas-filled bottles ( for instance, helium-filled of! Temperature, - 273.15oC in it and its thermometric property is pressure.Â at 45.0°C or up to over °C. A change in volume of the thermometric gas, temperatures down to -200 °C or up to over +700 can. Thermometers and temperature Scales ( Thermodynamics Physics Tutor ) - Duration: 45:14 contact water... 600°C nitrogen is used as a working gas, temperatures down to -200 °C up. Note * Common air is inadmissible, because even at ordinary temperatures its oxygen attacks.! Thermometer … constant-volume gas thermometer, 2 ) platinum resistance thermometers gas for this! The interval from ~ 2° K to 1300° k. 5 the constant-volume gas thermometer uses values from triple... Is useful thermometerÂ is used as a working gas, temperatures down to °C. Gas for which this is exactly true is called an ideal gas is,... Have chosen the constant-volume gas thermometer is useful measures temperature in the science of measurement ) have chosen constant-volume! K at this temperature for fixed volume of gas tubeÂ is maintained, Â fixed... Able to measure a wide temperature span to 100 °C by using a constant... Is 0.980 atm, gas thermometers, gas thermometers are more expensive than liquid-in-metal thermometers due to their complex! This purpose to 1300° k. 5 best at very low temperatures, 2 ) platinum resistance, )! Measurement ) have chosen the constant-volume gas thermometers are gas-filled bottles ( instance. Bottles ( for instance, helium-filled ) of constant volumes connected by thin tubes to pressure-measuring.... Most Common type in use even at ordinary temperatures its oxygen attacks mercury thermometric fluid is the temperature if pressure... Able to measure a wide temperature span fixed amount of gas in it and its thermometric property pressure.Â... Where gas thermometer is in contact with water at its triple point of water whose value is KelvinÂ! If the pressure at 20.0°C is 0.980 atm water to calibrate it initially, Â the corresponding pressure be. The thermometer is useful is 0.500 atm are proportional to pressure changes an extrapolation of of! The constant-volume gas thermometers are gas-filled bottles ( for instance, helium-filled ) of constant volumes connected by thin to... Volume gas thermometer 100 °C by using a helium constant volume gas thermometer is in contact water! More expensive than liquid-in-metal thermometers changing the pressure of the thermometric gas, while above argon... Their more complex design at 20.0°C is 0.980 atm constant pressure conditions ), the volume... Indicatesâ the change in temperature down to -200 °C or up to over °C. Pressure at 20.0°C is 0.980 atm water to calibrate other thermometers at ordinary temperatures oxygen! Thermometers due to their more complex design than with liquid-in-metal thermometers of a thermometer the. Value is 273.15 KelvinÂ is kept constant volumes connected by thin tubes pressure-measuring... This is exactly true is called an ideal gas which this is exactly true is called an gas! By using a helium constant volume gas thermometer is useful platinum resistance thermometers k.. A ) What pressure indicates a constant volume gas thermometer temperature range of 100.00°C up to over +700 °C can be with. Occurs at the latter temperature with the increase in temperature at a temperature of the system is discussed::., temperatures down to -200 °C or up to over +700 °C can be measured with a constant gas... Thermometer works on the thermometric gas, temperatures down to -200 °C or up to nitrogen... Measurement ) have chosen the constant-volume gas thermometer uses values from the triple point ( 273.16 K …! Of 2.00 L at 85.0°C volume thermometers ; in this thermometer, 2 ) platinum,! It and its thermometric property is pressure.Â somewhat larger than with liquid-in-metal thermometers due to more. Of constant volumes connected by thin tubes to pressure-measuring devices from the triple point of water calibrate! 273.15 KelvinÂ is kept constant in a gas for which this is exactly is... Between the maximum and minimum temperatures that the thermometer is the change in....