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    Model 425

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    Product Overview

    The Model 425 Flame Photometer (475 42 500) expands upon capability of the Model 420 Flame Photometer with addition of a detector and filter assembly specific for Calcium determination.  It also offers a “301 mode” feature which allows connection to a few of the more popular continuous flow systems.

    The Model 425 defaults to measurement with Lithium Internal Reference. This should be added to the blank, calibration standards and samples such that they all contain the same concentration of Lithium; i.e. ~ 100 ppm.  The Model 425 is supplied with Li solution 001 56 622. This should be diluted 1:10 with distilled water and the resulting solution used as the blank and to dilute the calibration standard and samples.  Sherwood Scientific can supply a 3 Molar solution of Li (001 56 603; 6x 100 ml) which when diluted 1:200 will give the optimum Lithium internal reference level. This is cheaper than using the 001 56 622 and is designed to be used with the Model 805 Dilutor where it is simultaneously diluted and mixed to the correct dilution for blank, calibrators and samples.

    The Model 425 Flame Photometer has RS232 output for printer or computer connection and is compatible with our Model 860 Autosampler for unattended sample analysis. The Model 425 may be used with the Model 805 Continuous Flow Dilutor, again in-conjunction with or without the Model 860 Autosampler and with or without BlueNotes 420 software

    A new optical arrangement implemented in 2018 gives improvement for the hitherto known issue of Sodium interference with Calcium determinations.  Previously reported interference was around the 4% mark and interference in newly manufactured units is now reduced to be less than 1% for samples containing equal concentrations of both Sodium and Calcium.

    • On board firmware with blanking, calibration and sample routines.
    • Simultaneous measurement of two of four elements: Sodium, Potassium, Calcium and/or Lithium.
    • Linearised Sodium response over the Sodium concentration range 0.5 to 20 ppm
    • Internal Reference facility (Lithium) for improved precision.
    • Automatic flame ignition and optimisation.
    • Safety features including optical flame and low air pressure detection for fuel gas shut off.
    • Two digital displays for calibration and analysis data of each channel; analogue outputs for use with chart recorders and some on-line analysers.
    • A “no tools” maintenance approach allowing easy access to mixing chamber and burner assembly.
    • RS232 for data output to a serial print

    Model 425 Flame Photometer (475 42 500) Specification


    Range Displayed

    Na 0.00 – 9.99; 10.0 – 199.9

    K 0.00 – 9.99; 10.0 – 199.9

    Li 0.00 – 9.99; 10.0 – 199.9

    Ca 0.00 – 9.99; 10.0 – 199.9


    Sample Concentration entering aspiration

    Na 0.5- 20 ppm

    K 0.5- 20 ppm

    Li 0 – 20 ppm

    Ca 5 – 100 ppm


    Na, K & Li Interference is < 0.5% value of element
    under analysis.  Na on Ca <1.0% for equal concentrations.


    (To be tested without Li Internal Standard)
    For Na, K, Li & Ca, with appropriate solution concentration, within the limits shown under Sample Concentrations (above), set at 100 will read 48-52 at midpoint ( Nominal 50).


    510mm x 390mm x 345mm 9.5 Kg  Net
    730mm x 450mm x 450mm 16.5 Kg  Packed


    Minimum Detection level =3 x noise
    Na 20 ppb
    K 20 ppb
    Li 50 ppb
    Ca 0.2 ppm

    Minimum Concentration to display 100 units

    Na 0.5 ppm

    K 0.5 ppm

    Li 0.5 ppm

    Ca 5.0 ppm

    Reproducibility (K=10 ppm 20 aliquots from single sample)

    With Li Internal Reference in operation < 0.5% CV

    Without < 1.0% CV

    Speed of analysis

    Variable (sample every 15-60 seconds) at user option

    Aspiration rate

    3-6 ml/min

    Minimum sample requirement

    1.5 ml (Diluted sample)

    Items included

    Model 425 2-Channel Flame Photometer
    Atomiser, Stainless Steel, complete
    Power Supply Unit Universal, IEC
    Tube, Drain
    Tube, PVC Reinforced, 2 Metres
    Tube, Gas 6.3 mm ID, 2 Metres
    Tube, Atomiser inlet
    1000 ppm Na (6 x 100ml)
    1000 ppm K (6 x 100ml)
    1000 ppm Li (6 x 100ml)
    1000 ppm Ca (6 x 100ml)
    Wire, Atomiser Cleaning PK of 3
    Lead, Instrument to Printer/PC
    Lead, Mails 2 Metres Black 10A IEC, Plain (no plug)
    Operator Manual
    BlueNotes 420 Software (Not CFR 21 Part 11 compliant)