New apparatus for measuring the density of mercury

Abstract

A new apparatus is being set up for measuring the density of mercury at 20 C with a relative uncertainty of 0.5 ϫ 10 -6 by hydrostatic weighing of a sinker of known volume and mass. Two small sinkers of about 50 cm 3 were calibrated by hydrostatic comparison with silicon density standards. Thus, in the first stage, a relative uncertainty of 2 ϫ 10 -6 of the mercury density can be reached. The quantity of mercury needed for the measurements is 1 l. Also, density comparisons of different mercury samples can be carried out with a relative uncertainty of 0.5 ϫ 10 -6 . To reach a relative uncertainty of 0.5 ϫ 10 -6 in the density of mercury, a 500 cm 3 hollow cube is to be manufactured from tantalum. Its volume will be determined by means of an interferometer, with a relative uncertainty of 0.15 ϫ 10 -6 . Measurements will be performed for the gravitation experiment of Zürich University using 1 m 3 of mercury, and for mercury samples used in primary pressure standards. Design and results of first tests of the hydrostatic weighing apparatus are reported.

Determination of the Gravitational Constant with a Beam Balance

“…The density of mercury samples taken from the upper and lower tanks was measured by the PTB. At a temperature of 20 C and a pressure of 101 325 Pa, a mercury density of 13 545:8904 kg=m 3 for the upper FM and 13 545:9504 kg=m 3 for the lower FM was obtained [9]. For the calculation of the gravitational force, a pressure and temperature correction has to be taken into account.…”

602. El barrio en cuestión. Fragmentación y despolitización de lo vecinal en la era neoliberal

“…66 Park, Burgess, & McKenzie, 1925 y constituye un refugio frente a una ciudad que se torna cada vez más impersonal. Para los miembros de la Escuela de Chicago, el vecindario representaba la continuación y supervivencia de formas de solidaridad social preindustriales dentro de la caótica gran ciudad 67 .…”

Present state of the solid and liquid density standards

“…Since natural mercury is a mixture of seven stable isotopes 196 Hg, 198 Hg, 199 Hg, 200 Hg, 201 Hg, 202 Hg, and 204 Hg, its density varies depending on the origin of the sample and on the purification process. When the densities of different mercury samples were compared at NPL [87], a maximum relative difference of 1.7×10 −6 was observed. This means that the absolute density value and its uncertainty in equation (34) apply only for the mercury sample still kept at NPL.…”

“…At PTB, an absolute measurement of the density of mercury is being conducted [87]. Details are given in this issue [88].…”