Posted in | Surface Analyzers

Micromeritics Gemini VII 2390 Series Surface Area Analyzers

Gemini VII provides accurate and quick surface area calculations.

  • Gemini employs a distinctive adaptive rate dosing algorithm and is a specialized instance of the static volumetric technique.
  • Swift surface area measurements with precision and no thermal-diffusion errors.
  • The strength of Gemini resides in its unique and innovative design. It is not just an accurate and reliable instrument but also an easily operable system with intuitive reporting.
  • Three model options are available to cater to diverse needs.
  • Capable of measuring the surface area of low-surface materials using N2.
  • Common mode rejection of free-space error effects.


Micromeritics' Gemini VII 2390 Series of surface area analyzers swiftly and reliably produce precise and reproducible surface area and porosity results. Renowned for its affordability, speed, user-friendly interface, reliability, and durability, the Gemini has become an essential instrument in laboratories globally for research and quality control purposes.

Features and Benefits

The distinct advantage of Gemini stems from its innovative design, providing not just a reliable and accurate instrument but also an easily operable system with intuitive reporting.

  • Innovation: Gemini employs a unique adaptive rate dosing algorithm, standing out as a special case of the static volumetric technique. Its unmatched speed and sensitivity surpass other static volumetric instruments.
  • Accuracy: Micromeritics created the balance tube design, eradicating free-space errors caused by thermal gradient variations or initial mismeasurements of free space. This innovation enables low surface area measurements without requiring krypton. A servo valve regulates gas flow into the sample tube, guaranteeing the precise attainment of target pressures without any pressure overshoot.
  • Faster Results: The sample governs the gas delivery rate, thus expediting the analysis of gas delivery. This results in a surface area analyzer that operates as swiftly as the physics of adsorption permits. On-screen how-to videos provide instructions, reducing training time for new users. Installation videos and system verification tests are easy to follow, ensuring optimal performance and reliability.
  • Flexibility: Three software control options: Embedded software enables operation without an external PC through the keypad; Windows 7 or greater operating system; Gemini VII Confirm™ with a 21 CFR Part 11 option designed for regulated pharmaceutical applications.

Three Instrument Options

  • Gemini VII 2390a: It is crafted for rapid and accurate surface area assessments through single-point and multipoint BET and Langmuir methods. This model also encompasses standard techniques for total pore volume evaluation, micropore analysis via the t-method, and additional functionalities. Notably, it possesses the ability to determine the statistical thickness surface area (STSA) specifically tailored for carbon blacks (refer 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, enabling continuous monitoring of the adsorptive’s saturation pressure during an analysis. This design feature allows for rapid measurement of the adsorption isotherm to near-saturation, as well as the determination of pore size distribution.
  • Gemini VII 2390t: With all the capabilities of the 2390p, including a Po tube, this model comes equipped with a larger Dewar and extended sample tubes for prolonged analyses. This enhancement allows for the measurement of the entire adsorption-desorption process. Leveraging this extensive dataset, users can perform a BJH or Dollimore-Heal pore size distribution analysis using a maximum of 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

Micromeritics Gemini VII 2390 Series Surface Area Analyzers

Image Credit: Micromeritics Instrument Corporation


Sample Preparation Devices

Micromeritics presents a variety of sample preparation instruments tailored for surface area and pore volume analysis. These instruments employ a mix of flowing gas, vacuum, and heat to eliminate atmospheric contaminants like water vapor and adsorbed gas from the sample's surface and pores.

The accuracy of data obtained from surface area and pore volume analyses significantly relies on the cleanliness of the sample surface. Micromeritics' sample preparation devices are compatible with N2, He, Ar, and other non-corrosive gases to ensure versatility in operations.

FlowPrep™ 060

The FlowPrep™ 060 utilizes heat and a stream of inert gas to treat the sample. The heat triggers the desorption of contaminants from the surface, while the inert gas stream efficiently removes these contaminants from the sample tube.

This unit provides adaptability by allowing the user to choose the ideal temperature, gas type, and flow rate optimally suited to the specific sample material and application. The incorporation of needle valves enables precise control over the introduction of flowing gas, preventing sample fluidization.

Micromeritics Gemini VII 2390 Series Surface Area Analyzers

Image Credit: Micromeritics Instrument Corporation

VacPrep™ 061

The VacPrep 061 offers two distinct techniques to remove contaminants. Alongside the option of using flowing gas, it allows for the application of a vacuum during sample preparation via heating and evacuation. This dual approach empowers users to select the preparation method that best suits their material or application needs.

The VacPrep comprises six degassing stations, providing the option for vacuum or gas flow preparation at each station. Additionally, the inclusion of needle valves enables a gradual introduction of flowing gas or vacuum, effectively preventing sample fluidization.

Smart VacPrep™ 067

The Smart VacPrep™ 067 is an advanced six-port system that employs a vacuum for sample preparation via heating and evacuation. Each port within this system can be operated independently, allowing users to add or remove samples from degas ports without interrupting the treatment of other samples in the preparation sequence. The degassing process automatically halts upon completion of all programmed steps for the samples.

Smart VacPrep 067.

Smart VacPrep 067. Image Credit: Micromeritics Instrument Corporation

Cryogen Transfer System

The Micromeritics Cryogen Transfer System streamlines the transfer of liquid nitrogen or liquid argon from a nonpressurized storage dewar into smaller containers used in laboratory experiments. Additional accessories are also accessible for specific and 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 used with embedded software from a keypad or with the more robust and flexible Gemini Windows optional software from a computer.

The embedded software includes:

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

Optional Gemini Windows Software

The user-friendly Gemini Windows 7 interface enhances the process of planning, launching, and overseeing analyses. It streamlines the collection, organization, archival, and processing of raw data. Additionally, it simplifies the storage of standardized sample information and analysis conditions, ensuring easy retrieval for future applications.

Users can generate completed reports on the screen, in print, or as files in various formats. Notable features include 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 simultaneously 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-entered data
  • Installation and instructional videos
  • Summary report
  • Overlay of isotherm plots
  • Automatic generation of pressure tables with user-selected endpoints
  • Storage of all historical sample data for retrieval
  • User-defined pressure table
  • Sample log available
  • Cut-and-paste graphics and tables
  • Cumulative and differential data
  • Fixed pore size tables
  • Data export to ASCII and spreadsheet formats
  • Autoscaling of x- and y-axes
  • User-defined thickness curve (manual entry or from a data file)
  • Linear and logarithmic plots (isotherm, pore volume, pore area)
  • Broekhoff-de Boer thickness curve

21 CFR Part 11 Option

The Confirm software is additionally available, which is designed to meet the diverse requirements outlined by 21 CFR Part 11. It encompasses validation, security measures, audit trails, reporting functionalities, and other crucial aspects essential for compliance.

Micromeritics Gas Adsorption Reports

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

Isotherm Reports:

  • Graphical
  • Tabular
  • Pressure composition isotherm

Isotherm modeling and surface area:

  • Langmuir
  • Freundlich
  • BET
  • 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 utilizing Ar, N2, or CO2
  • Comes with a windows-shaped model for pillared clay
  • Cylindrical pores available for hydrogen–or ammonium-exchanged zeolites using N2 or Ar
  • Cylindrical pores for alkaline exchanged zeolites using N2 or Ar

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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