Absolute viscosity of water at 20-degrees-C

Abstract

An accurafu knowl edge of t he viscos it ies of liquids in absolute units is of fundamental importance in man y scient ifi c fi elds. Th e meas urement of t hese viscosities is almost universally based upon the absolute viscos ity of water at 20° C as a primary standard. During t he past 50 years t here has been an in creasing need for a more accurate d eterminat ion of t his s tandard. Consequen t ly, with t he coopera tion of t he Society of Rheology and so me financial assistance from t he Chemical Foundation , this proj ect was undert aken by t he National Bureau of Standards and has now been completed.Th e determination was made by t he method of capillary fiow. By means of a calibrated i nj ector, va riou s known constan t rates of flow were prod~c e d in capillaries of m eas ured dim ensions and obser vations were made of the co rrespondmg press ure drops through t he capillari es.' Th e eff ects of t he ends of t he capillaries were r endered negligible by t he s imu ltan eo us t reatment of da ta obt ained with pairs of capi llaries having essent ia lly t he same diam eters but differen t lengths.The value found for t he viscos ity of water is 0.010019 poise as co mpared wi th 0.01005 poise, which has generally been accepted for t he past 30 years. Th e estimated accuracy o f t he !lew determination is ± 0.000003 poise.As a r es ult of this work, begin nin g 0 11 JIIly 1, 1952, the Nat ional Bureau of Standards is plannin g to use t he value 0.01002 poise for t he absolu te v iscos ity of wa:ter at 20° C a s t he basis for the calibrat ion of viscometers and standard-sample otis. It] S r eco mm end ed t hat other laboratories adopt t his value as t he primary refere nce standard for co mparative m eas urem ents of viscosity.

Vibrating-wire viscometers for liquids at high pressures

“…The present viscometers contain elements subject to attack by water, for which the viscosity is known to within _+0.1% [16]. Thus, it has been necessary to calibrate the instrument with respect to reference data for some liquid hydrocarbons.…”

Validation of a Vibrating-Wire Viscometer: Measurements in the Range of 0.5 to 135 mPa·s

“…1,2 As a first step, the Bureau International des Poids et Mesures (BIPM) together with the former Subcommittee on Transport Properties 19 of the Physical Chemistry Division of IUPAC has initiated a search for a standard reference fluid with a viscosity in the range of (100 to 200) mPa‚s. 3 One fluid identified for this purpose is diisodecylphthalate (DIDP), which was the subject of an earlier preliminary study.…”

Vapor pressure of nitrogen

“…The manometer used is a version of one describ ed by Swindells, Coe, and Godfrey [2] modilied in such a way as t o make an absolute pressure-readinO' instrument. In thi manometer the m er cury surf~ces are lo cated by touching th em with stainless-steel rods of calibrated lengths.…”

“…The liquid volumes used wer e those of Mathias, Onnes, and Orommelin. The satura ted vapor densi Ly derived from the vaporpressure data may be r epresented by eq (2) It should be noted that the revised value for the vapor density given by Crommelin at 64.80° K is incompatible with the behavior of a r eal gas near its saturation line, as it is less than ideal gas density at this temperature and pressure.…”