Device for measuring the activity of a liquid in a complex medium and associated method

Patent metadata

Field	Value
Publication number	US-9316572-B2
Application number	US-201013508169-A
Country	US
Kind code	B2
Filing date	Nov 4, 2010
Priority date	Nov 4, 2009
Publication date	Apr 19, 2016
Grant date	Apr 19, 2016

Abstract

A device for measuring the activity of a liquid in a complex medium and an associated method, the device comprising a sealed enclosure in which the complex medium is intended to be placed and means for maintaining this enclosure at a constant temperature T, characterized in that it comprises: a means ( 14 ) for modifying the total volume of the enclosure; a pressure sensor ( 22 ) for measuring the total pressure in the enclosure; and means ( 24 ) for calculating the activity of the liquid in the complex medium from the temperature T, from the total volume of the enclosure and from the total pressure in the enclosure.

First claim

The invention claimed is:

1. A device for measuring the activity of a liquid in a complex medium, comprising a sealed enclosure, said enclosure being also an isotherm enclosure which is therefore capable of maintaining this enclosure at a constant temperature T and in which the complex medium is intended to be placed, wherein the device comprises:
a means for modifying the total volume of the enclosure;
a pressure sensor for measuring the total pressure in the enclosure;
a means for calculating the activity of the liquid in the complex medium, from the temperature T of the enclosure, the total volume of the enclosure and the total pressure in the enclosure.

2. The device for measuring the activity of a liquid in a complex medium as claimed in claim 1 , in which the means for modifying the total volume of the enclosure is a piston which can be displaced to modify this volume, one face of said piston forming a wall of the enclosure.

3. The device for measuring the activity of a liquid in a complex medium as claimed in claim 2 , in which the enclosure is formed by a cylinder sealed at one of its ends by a sample-holder and, at its other end, by said face of the piston.

4. The device for measuring the activity of a liquid in a complex medium as claimed in claim 3 , in which the cylinder is mounted on rods, which are in turn mounted on a baseplate of the device.

5. The device for measuring the activity of a liquid in a complex medium as claimed in claim 4 , in which the sample-holder is mounted on a base, which is in turn mounted on the baseplate.

6. The device for measuring the activity of a liquid in a complex medium as claimed in claim 3 , in which means are provided to displace the piston in the cylinder.

7. The device for measuring the activity of a liquid in a complex medium as claimed in claim 3 , in which a graduated drum is provided to identify the position of the piston in the cylindrical tube.

8. The device for measuring the activity of a liquid in a complex medium as claimed in claim 3 , in which a sump is provided, arranged inside the sample-holder.

9. A method for measuring the activity of a liquid in a complex medium, wherein the method comprises the steps consisting, after having placed the complex medium in a sealed enclosure, said enclosure being also an isotherm enclosure which is therefore capable of maintaining this enclosure at a constant temperature T, in:
(a) performing a basic increment Δv j of the enclosure volume;
(b) after having reached the thermodynamic balance between the complex medium and the enclosure, maintaining the total pressure p i , measured in the enclosure;
(c) determining a relationship (R1) between the total pressure p i , the partial liquid vapor pressure at balance p veq and the partial pressure of the ideal gas not being dissolved, for example air, the latter being expressed using the ideal gas law, such that the relationship (R1) is expressed:

p
i

=

p
veq

+

n
a

⁢

RT

v
i

(

R
⁢

⁢
1

)

in which:
R is the ideal gases constant;
n a is the number of moles of the ideal gas not being dissolved;
v i is the total volume of the enclosure, defined by the relationship:

v
i

=

v
0

+

∑

j
=
1

i

⁢

⁢

Δ
⁢

⁢

v
j

with v o being the initial volume of the enclosure
(d) repeating steps (a) to (c) n times, with n>1 if the initial volume of the enclosure is known or n>2 otherwise, to deduce therefrom the value of the partial balance vapor pressure p veq ; and
(e) calculating the activity of the liquid a w in the complex medium by the following relationship (R2):

a
w

=

p
veq

p
vs

⁡

(
T
)

(
R2
)

in which:
p vs (T) is the saturating vapor pressure of the pure liquid at the temperature T.

10. The method for measuring the activity of a liquid in a complex medium as claimed in claim 9 , in which the step (d) consists in repeating the steps (a) to (c) at least 5 times.

Assignees

• Benet Jean-Claude
• Cousin Bruno
• Cherblanc Fabien
• Ouoba Samuel
• Centre Nat Rech Scient
• Univ Montpellier 2

Inventors

• Benet Jean-Claude
• Cousin Bruno
• Cherblanc Fabien
• Ouoba Samuel

Classifications

• G01N7/14 Primary

  by allowing the material to emit a gas or vapour, e.g. water vapour, and measuring a pressure or volume difference {(determining urea G01N33/48742)} · CPC title

• G01N3/08

  by applying steady tensile or compressive forces (G01N3/28 takes precedence) · CPC title

• G01N2203/0085

  Compressibility · CPC title