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Gemini Technique Overview

Unique Design

Micromeritics’ Gemini utilizes an adaptive rate, static volumetric technique. It is the first gas sorption method that adapts the rate at which gas is delivered to the sample to the rate at which it is adsorbed. Each pressure point is allowed to equilibrate before the next point is taken. The Gemini has two gas reservoirs which are filled with equal volumes of the desired adsorptive, usually nitrogen. From the reservoirs, gas is metered into the sample and balance tubes by way of a servo valve that reacts to the rate of adsorption. A transducer monitors pressure within the sample tube. In a typical dose-and-wait analytical system, pressure within the sample tube decreases after each dose as the sample adsorbs gas. This is not the case with the Gemini. Transducer causes a fast response servo valve to increase or restrict the flow of gas to the sample tube as necessary to maintain a constant equilibrium pressure within the sample tube as adsorption occurs. Transducer located between the sample and balance tubes detects any pressure difference between the two tubes and causes another servo valve to adjust the pressure within the balance tube to negate any pressure differential. A third pressure transducer monitors the pressure between the two reservoirs to determine the differential quantity of gas, the difference being the quantity that is adsorbed on the sample. These methods of dosing and differential quantity detection enable the Gemini to accurately determine adsorption characteristics at a speed and sensitivity level unsurpassed by other static volumetric instruments.


Below is Part 1 of our webinar on physical adsorption. Parts 2 and 3 can be found on our Archived Webinars webpage.