The range oyer which thermodynamic temperatures have been realized by gas t hermometry at the NBS has been extended to 730 K. The results are preserved by measu ring the corresponding international practical temperatures. The difference b etween them is ex pressed as the foll owing polynomial : 8= -120,887.784/ T.i + 1213.53295/ T 68 -4.3159552 + 6.44075647 X 10-3 T 68 -3.56638846 X 1 0-6 T6~ which is valid in the range 273 to 730 K.The difference found and the es timated uncertainties at the t h ree defining fixed points in the range covered arc
A mercury manometer using capacitance sensing of meniscus positions has been refined to give an accuracy within 2 parts in 108 of the pressure in the range from 1 x lo4 to 1.3 x 105 N/ma. The determination of pressure ratios is accurate within 1.5 parts in 1 0 6 for pressures in the same range.
The va por pressu re of wate r at its tri ple point was meas ured with exce pti onall y hi gh acc uracy by reali zing it with a special a ppara tu s and meas urin g the press ure with the NBS precision merc ur y ma nome ter. The va por press ure a pparatus had a syste m for c irc ul ating th e liqui d wa te r. Actu al triple point con diti ons we re es ta bli shed with a thin sheet of fres hl y distill ed liquid Rowin g dow n over a n ex pose d man tle of ice froze n on a verti cal well. T hi s tec hnique redu ced non-volatil e co nta min an ts a nd th e va por was re peatedl y pumped to re move acc umul ated volatile conta min a nts. A di aph ragm press ure tra nsd uce r was used to se pa ra te th e wa te r va por from th e he lium used to trans mit th e press ure to th e manomete r. The valu e fou nd for th e va por press ure of water at its tri ple po int was 61 1.657 Pa with an un ce rtainty of ± 0.010 Pa fro m ra ndom e rrors, co mputed a t 99 percent confid e nce li mits. Th e sys te ma ti c e rrors a re estima ted to be in s ignifica nt relati ve to th e ra nd om e rrors.Key word s: Prec ision me rc ury ma nometer; tri ple point of wate r; vapor pressu re of wa ter.
The investigation of the effects of sorption in a gas thermometer used to realize the Thermodynamic Kelvin Temperature Scale has been continued. By eliminating sorbable material more completely from the gas thermometer. we attained higher gas purity. So little contaminant re mained that further cleanup produced no significant effect on the values of thermodynamic temperatures measured between 0 °C and 142°C. The results are presented by giving the differences between the values on the thermodynamic scale and the International Practical Temperature Scale of 1968. The value of the steam point was deter· mined to be 99.970 °C(therm} with an uncertainty of ± 3.5 mK at the 99 percent confidence level (based on 3 times the estimate of the standard deviation).
Gage bloc ks can be join ed by "wringin g" to produce a vacuum-tight joint. Hoke gage blocks have square gagi ng surfaces with a ce ntral hol e co nnecting them. The qualit y of th e joints bet ween blocks can be tested by measurin g the vacu um leak rates throu gh th e joints into the ce ntral hol e. Wh en two Hok e bloc ks are in contact at one edge but tilted at a n angle cf>, the vacuum leak rate into a chamber of 22 c m 3 IJrodu ces a rate of pressure increase which can be represented by the foll owin g po lynom ial : dp/dt = 0.42 cf>2 + 0.022 cf>3 /1-m Hgfmin , where cf> is in /1-rad. Hoke blocks in suitabl e condition to be joined by wringing ca n also be joined by alining them and evacuating the joint through the center hole.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.