Gemini VII Series Surface Area Analyzer From Micromeritics

Gemini VII delivers accurate and quick surface area analysis.

  • Gemini uses a distinctive adaptive rate dosing algorithm, representing a special case of the static volumetric technique.
  • The strength of Gemini resides in its innovative and unique design, providing a reliable and precise instrument. It also features an easy-to-use operating system, accompanied by intuitive reporting.
  • Capable of accurately measuring materials with low surface area using N2.
  • Quick surface area measurements with accuracy and no thermal-diffusion errors.
  • Three model options are available to accommodate needs.
  • Exhibits common mode rejection of free-space error effects.


The Gemini VII 2390 Series of surface area analyzers from Micromeritics reliably and quickly generate accurate and reproducible surface area and porosity outcomes.

These instruments have gained global recognition in laboratories worldwide for their speed, affordability, user-friendly operation, reliability, and robustness, establishing the Gemini as an indispensable tool in research and quality control settings.

Features and Benefits

The advantageous capabilities of the Gemini stem from its distinctive and innovative design. It is reliable, and accurate, and boasts an intuitive operating system that makes reporting effortless.

  • Innovation: Gemini employs a distinctive adaptive rate dosing algorithm. It is a special case of the static volume technique. Its sensitivity and speed surpass other instruments using the same technique.
  • Accuracy: Micromeritics introduced the balance tube design, eliminating free-space errors due to thermal gradient variations or initial mismeasurement of free space. The Gemini enables low surface area measurements without requiring krypton, and a servo valve controls the gas flow into the sample tube to ensure precise target pressures without overshooting.
  • Faster Results: The sample regulates the gas delivery rate, expediting the analysis of gas delivery. This feature makes the surface area analyzer as fast as the physics of adsorption allows. Instructional videos offer on-screen guidance for operating instruments, reducing the training time for new users. Installation videos and system verification tests that are easy to follow are provided to ensure optimal performance and reliability.
  • Flexibility: Three software control options are available. Embedded software allows operation without an external PC via the keypad. It is compatible with Windows 7 or higher operating systems. Additionally, Gemini VII Confirm™ offers a 21 CFR Part 11 option for regulated pharmaceutical applications.

Three Instrument Options:

Gemini VII 2390a: Ideal for swift and precise surface area determinations through single-point and multipoint BET and Langmuir methods.

It also offers standard methods for total pore volume, micropore analysis using the t-method, and more. It includes the ability to determine the statistical thickness surface area (STSA) of carbon blacks (adhere to ASTM D 6556, ASTM D 3765, ISO/DIS 18852.2, or ISO/CD 4652-2/3).

Gemini VII 2390p: Enhances precision by incorporating a saturation pressure (Po) tube, allowing continuous monitoring of the adsorptive’s saturation pressure during an analysis. This design enables rapid measurement of the adsorption isotherm to near-saturation and facilitates the determination of pore size distribution.

Gemini VII 2390t: Possesses all the capabilities of the 2390p, including a Po tube, along with a larger Dewar and longer sample tubes for extended analyses. This provides the additional capability to measure the total adsorption-desorption process. With this dataset, one can conduct a BJH or Dollimore-Heal pore size distribution utilizing up to 1000 data points.


Source: Micromeritics Instrument Corporation

Surface Area From 0.1 m², total; From 0.01 m²/g, specific
Pore Volume 4 x 10-6 cm³/g
Pressure Measurement
Pressure Measurement Range 0 to 950 mm Hg
P/Po Resolution <10-4
Relative Pressure Range 0 to 1.0 P/Po (desorption available only on 2390t)
Pressure Resolution <0.1 mmHg
Accuracy and Linearity (transducer manufacturer’s specification) Better than ± 0.5 % Full Scale
Operating Environment
Temperature 10 to 35 °C (50 to 96 °F) operating; 0 to 50 °C (32 to 122 °F) non-operating
Humidity 20 % to 80 % relative, non-condensing
Adsorbate Optimized for nitrogen in a liquid nitrogen sample bath; Gemini may be used with non-corrosive adsorbate gases having vapor pressures at both room and bath temperatures that are acceptably high relative to the resolution of the 1000-mmHg pressure transducer. Typically, oxygen, argon, carbon dioxide, butane, methane, and other light hydrocarbons will produce useful data above absolute pressures of a few mmHg. Helium inlet also provided
Vacuum System
Vacuum source achieving 20 x 10-3 mmHg (or better) at the instrument inlet; having a device to reduce oil vapor backstreaming is recommended. The system must have an anti-suckback valve to prevent oil from being admitted into the Gemini should there be a power failure.
Sample Tube/Dewar
Standard Tube Gemini VII 2390a and 2390p: 0.95 cm (3/8 in.) outside diameter by 15.5 cm
(6.1 in) with 6.5 cm³ of volume. Sample capacity is approximately 2.0 cm³ Gemini VII 2390t: 0.95 cm (3/8 in) outside diameter by 20.5 cm
(8.1 in.) with 8.9 cm³ of volume. Sample capacity is approximately 2.0 cm³
Dewar ~ 8 hours; Gemini VII 2390a and 2390p; ~ 24 hours; Gemini VII 2390t
Voltage 85 to 265 VAC
Frequency 50/60 Hz
Power 150 VA, operating, max. plus vacuum pump
Height 59 cm (23 in); Gemini VII 2390a and 2390p; 74 cm (29 in); Gemini VII 2390t
Width 40 cm (16 in)
Depth 51 cm (20 in)
Weight 32 kg (70 lbs); Gemini VII 2390a and 2390p; 35 kg (78 lbs); Gemini VII 2390t



Unique Design: The Gemini Technique

Gemini VII Series Surface Area Analyzer From Micromeritics

Image Credit: Micromeritics Instrument Corporation


Sample Preparation Devices

Micromeritics provides a variety of sample preparation instruments for surface area and pore volume analysis. These instruments utilize a combination of flowing gas and/or vacuum along with heat to eliminate atmospheric contaminants, including water vapor and adsorbed gas, from the surface and pores of the sample.

The accuracy of data obtained from surface area and pore volume analyses is significantly influenced by the cleanliness of the sample surface. All Micromeritics sample preparation devices are compatible with N2, He, Ar, and other non-corrosive gases.

The FlowPrep™ 060

The FlowPrep™ 060 applies heat and a stream of inert gas to the sample. Heat induces contaminants to desorb from the surface, while the inert gas stream removes them from the sample tube.

This unit enables users to select the temperature, gas, and flow rate best suited to the specific sample material and application. The inclusion of needle valves allows for a controlled introduction of the flowing gas, preventing the fluidization of samples.

Gemini VII Series Surface Area Analyzer From Micromeritics

Image Credit: Micromeritics Instrument Corporation

The VacPrep™ 061

The VacPrep™ 061 provides two techniques for eliminating contaminants. As well as flowing gas, it allows the application of a vacuum for sample preparation through heating and evacuation. This dual approach enables users to select the preparation method that best suits their material or application.

The VacPrep includes six degassing stations, offering a selection between vacuum or gas flow preparation on each of the six stations. Needle valves are also incorporated, allowing a gradual introduction of the flowing gas or vacuum to prevent the fluidization of samples.

The Smart VacPrep™ 067

The Smart VacPrep™ 067 is a sophisticated six-port system that employs a vacuum for sample preparation through heating and evacuation.

Each port on this system can be operated independently, enabling the addition or removal of samples from degas ports without disrupting the treatment of other samples in the preparation process. The degassing process automatically concludes once the samples have completed all programmed steps.

Smart VacPrep™ 067.

Smart VacPrep™ 067. Image Credit: Micromeritics Instrument Corporation

Cryogen Transfer System

The Micromeritics Cryogen Transfer System facilitates the transfer of liquid nitrogen or liquid argon from a nonpressurized storage dewar into smaller containers employed in laboratory experiments. Supplementary accessories are also available for specialized applications.

Model O21 LN2 Transfer System.

Model O21 LN2 Transfer System. Image Credit: Micromeritics Instrument Corporation

Consumables and Supplies

Source: Micromeritics Instrument Corporation

Part Number Description Notes
004-62230-58 Gas Regulator, CGA 580 30 psig; Compatible with Ar, He, Kr, and N2
004-33601-00 Expansion Kit Adds additional outlet to gas regulator. Includes fittings and instructions
004-33602-00 Pressure Relief Kit Prevents excessive gas pressure in event of regulator failure. Not to be used with noxious gas. 
201-25818-01 Stainless Steel Gas Inlet Line 5m (16 ft.)
290-25846-01 Copper Gas Inlet Line 5m (16 ft.)
290-25846-00 Copper Gas Inlet Line 6 ft. 
236-61702-00 Gemini 3/4 in OD Bulb Sample Tube  3/4-in. (19.1-mm) OD bulb x 6.1-in. (155-mm) long, approx. 9 cm³ sample capacity
238-61703-00 Gemini 3/8 in OD Straight-Wall Long Sample Tube  3/8-in. (9.6-mm) OD x 8.0-in.(203-mm) long, approx 2 cm³ sample capacity
236-61707-01 Gemini 5/8 in OD Straight-Wall Sample Tube  5/8-in. (16-mm) OD x 0.53-in. (13.5-mm) ID x 6-in. (152 mm) long
236-61703-00 Gemini 3/8 in OD Straight-Wall Sample Tube 3/8-in. (9.6-mm) OD x 6.1-in. (155-mm)
239-33010-00 Gemini 0.5395 in (16 mm) Sample Tube Kit  0.5395 in (16 mm) sample tube kit consisting of: 2 sample tubes with stoppers, 16 OD., 2 hanging filler rods, 2 connectors with hooks attached, two connector nuts, 2 O-rings, 2 ferrules, 1 open end wrench, Left and right Dewar covers, modified
236-61704-00 Filler Rod for Balace and Sample Tube 7 mm X 146.1mm
236-61705-00 Filler Rod for Sample Tube  7 mm X 101.6 mm
236-61708-00 Hanging Filler Rod  13 mm OD
236-61706-00 Hanging Filler Rod  7 mm OD
236-61709-00 Hanging Filler Rod  25.4 mm OD
280-32800-00 Sample Tube
Weighing Support 
For supporting sample tubes while weighing
240-25853-00 Powder Funnel Nylon
240-14855-00 Sample Tube Rack For holding sample tubes
004-54611-00 Cleaning Brush for Straight Wall Sample Tube Brush, 8 mm DIA X 50 mm X 190 mm LG.
004-54612-00 Cleaning Brush for Bulb Sample Tube  Brush, 25 mm DIA X 25 mm X 240 mm LG.
004-32004-00 Rubber Stopper for Sample Tube Help prevent sample contamination in the atmosphere
004-61065-00 3 mm Glass Beads 90 grams; for displacing volume in the balance tube equivalent to the volume of sample in the sample tube when analyzing high volume, low surface area samples.
004-25022-00 Duro Buna-N O-Ring Size 12 for sealing 3/8 in. OD sample tube stem
004-25466-00 Duro Buna-N O-Ring Size 10 for sealing the filter disk
004-27046-00 Sample Tube Port Frit 40 microns; 1/4'' D X 1/16 '' tall 
004-27024-00 Balance Tube Port Frit 2 microns; 1/4 '' D X 1/16 '' tall
004-61064-00 600 mL Dewar for Gemini VII 2390a,VII 2390p
239-33601-00 2.2 L Stainless Steel Dewar Kit includes dewar cover; for Gemini VII 2390a, 2390p 
239-33602-00 4.0 L Stainless Steel Dewar Kit includes dewar cover; for Gemini VII 2390t
239-31802-00 Insulating Dewar Cover for 2.75L Dewar  
236-31802-01 Cover, Dewar Right Active 32
236-31802-02 Cover, Dewar Left Active 33
062-00000-11 110/120V Vaccum Pump with built-in anti-suckback valve; Includes vacuum hose, fittings, exhaust filter, oil and manual
062-00000-23 220/240V Vaccum Pump with built-in anti-suckback valve; Includes vacuum hose, fittings, exhaust filter, oil and manual
004-16003-01 1L Vaccum Pump Oil for vaccum pump
200-25879-00 Funnel for Vaccum Pump Oil  for vaccum pump
004-27040-00 Vacuum Pump Exhaust Filter for vaccum pump
062-33002-00 Oil Vapor Trap  for vaccum pump
004-16830-00 Activated Alumina Pellets 500 g; for oil vapor trap
236-42701-01 French Keypad Template  
236-42701-02 German Keypad Template  
236-42701-03 Spanish Keypad Template  
236-42701-04 Italian Keypad Template  
003-5113-00 Slow-Blow Fuse 3 AG, 1.5 A
065-25811-00 Isothermal Inserts for Gemini Bulb Tube  
065-25812-00 Isothermal Inserts for Gemini Straight Wall Tube  
061-33001-00 Flow Control Valve Kit regulates gas flow and/or vacuum on sample preparation units; includes six flow control valves and instructions.
239-33005-00 Gemini VII Prep Seal Kit  used to degas and transfer air-sensitive samples to an analysis port without contamination.
008-42001-00 Analytical Methods in Fine Particle Technology by Paul A. Webb and Dr. Clyde Orr This book has been prepared to serve those just entering this field of technology as well as experienced researchers seeking insight into particular problems and guidance in achieving the utmost from their testing and research.
200-42901-00 Gas Adsorption Theory Poster 24'' X  36''
200-42902-00 Gas Adsorption Apparatus Poster 24'' X  36''
239-42802-00 Gemini VII Operators Manual Gemini 2390, V1.04
061-00023-00 VacPrep 061 Degasses up to six samples at up to 400 °C with either flowing gas or evacuation (evacuation requires a vacuum pump and gas regulator).
060-00023-00 FlowPrep 060 Degasses up to six samples at up to 400 °C  with flowing gas (requires a gas regulator)
202-33027-00 MicroActive
Data Analysis
Software V6.00
Micromeritics’ innovative MicroActive software allows users to interactively evaluate isotherm data from Micromeritics ASAP, TriStar, and Gemini gas adsorption instruments. Users can easily include or exclude data, fitting the desired range of experimentally acquired data points using interactive, movable calculation bars. Isotherms can be viewed on either a linear or logarithmic scale and available to the user under each calculation model. No need to generate reports to review results – now see it graphically and interactively on screen.
025-00239-00 Chiller Dewar for Gemini 2390t A closed plumbing system that circulates fluid from a temperature-controlled bath into a small dewar filled with antifreeze in which the sample tubes are immersed
004-16833-00 Carbon Black Reference Material  SA, approximately 30.6 m²/g
004-16858-00 Alumina Reference Material SA, approximately 5.2 m²/g



Operating Software

Gemini analyzers can be controlled from a computer with the more capable and flexible Gemini Windows optional software, or via a keypad with embedded software.

The embedded software includes:

  • System verification tests
  • Langmuir surface area determination
  • Total pore volume measurement
  • Single- and Multipoint BET (Brunauer, Emmett, and Teller) surface area analysis
  • Horvath-Kawazoe for micropore distribution analysis 
  • Total micropore volume and area using the t-Plot Method with Halsey, Harkins-Jura, or Carbon Black STSA thickness curves
  • BJH adsorption and desorption isotherm, 1000 Data Points (Gemini 2390t only)
  • BJH Pore size distribution using adsorption isotherm (Gemini 2390p and 2390t only)

Optional Gemini Windows Software

The user-friendly Gemini Windows 7 interface elevates the functionality for planning, launching, and controlling the analysis. It enables the collection, organization, archiving, and processing of raw data, while also facilitating the storage of standardized sample information and analysis conditions for convenient retrieval in subsequent applications.

Completed reports can be generated on the screen, in print, or as files in diverse formats. Noteworthy features encompass cut-and-paste graphics and tables, scalable and editable graphs, and customizable report formats. With computer control, users can operate up to four Gemini analyzers concurrently from a single computer.

Gemini Windows® Features

The Gemini Windows software offers supplementary features not encompassed in the embedded software.

Features such as:

  • Minimization of user-input data
  • Installation and instructional videos
  • Automatic generation of pressure tables with user-selected endpoints
  • Summary report
  • Archive of all historical sample data for retrieval
  • User-defined pressure table
  • Overlay of isotherm plots
  • Sample log
  • Cut-and-paste functionality for graphics and tables
  • Data export to ASCII and spreadsheet formats
  • Autoscaling of x- and y-axes
  • Fixed pore size tables
  • Cumulative and differential data
  • User-defined thickness curve (manual entry or from a data file)
  • Broekhoff-de Boer thickness curve
  • Linear and logarithmic plots (isotherm, pore volume, pore area)

21 CFR Part 11 Option

Confirm™ software is also available, catering to the numerous stipulations outlined by 21 CFR Part 11, covering validation, security, audit trails, reporting, and more.

Micromeritics Gas Adsorption Reports

The Windows software accompanying all of Micromeritics' gas adsorption instruments includes the following reports:

Isotherm Reports:

  • Graphical
  • Tabular
  • Pressure composition isotherm

Isotherm modeling and surface area:

  • Langmuir
  • BET
  • Freundlich
  • Temkin

Standard isotherm models:

  • t-plot: micropore volume, micropore area, external surface area
  • f-ratio method
  • alpha-s method

Classic models for mesopore volume, area, and distribution:

  • BJH
  • Dollimore-Heal

Classic models for micropore distribution:

  • Dubinin-Radushkevich and Astakhov
  • Saito-Foley
  • Horvath-Kawazoe
  • Cheng-Yang
  • MP method

Density Functional Theory for pore size modeling

  • Slit-shaped pores using Ar, N2, or CO2
  • Cylindrical pores for alkaline exchanged zeolites using N2 or Ar
  • Cylindrical pores for hydrogen–or ammonium-exchanged zeolites using N2 or Ar
  • Windows-shaped model for pillared clay

Density Functional Theory for Surface Energy

  • Surface area and energy distributions using nitrogen at 77 K
  • Surface area and energy distributions using argon at 87 K
Micromeritics Gemini VII 2390 Surface Analyzer

Video Credit: Micromeritics Instrument Corporation 

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