Rank Brothers Ltd

Photometer Cell

Charge Analyser with Photometer Cell

The Photometer Cell enhances the Charge Analyser II by carrying out a photometric titration using Toluidine blue indicator to detect the end point. This method will be familiar to many people already carrying out manual titrations. The cell is a stainless steel cylinder containing the optical components plus associated electronics. The electronics measure the relative transmission of light through the sample, and thus the cell is able to detect when the indicator turns from blue to pink or vice versa.

The Titration

The Charge Analyser II uses a different strategy for titrating with the photometer cell, than with the streaming current cell. Fixed doses of polymer (20 µl) are added to the sample until the unit has detected a significant colour change and that the colour has become stable, thus the dosing typically continues for over 1ml after the colour change has occurred. The titration data is then scanned and processed to determine the end point of the titration.

Streaming Current Cell vs. Photometer Cell

There are advantages to both types of cell as listed below.

Streaming Current Cell

Advantages Disadvantages
Greater accuracy than photometer cell. Needs careful cleaning for maximum accuracy.
Not affected by calcium ions. Cannot cope with low molecular weight materials.
Titration not complicated by addition of cationic indicator. Heavier and larger than photometer cell.

Photometer Cell

Advantages Disadvantages
Lighter and smaller than the streaming current cell therefore more portable. Less accurate than the streaming current cell.
Easily cleaned. The indicator is cationic; allowance must be made for this in the titration.
Uses a familiar technique. The Toluidine blue indicator is affected by various metal ions, particularly calcium and aluminium.
Titrates low molecular weight chemicals.


All CAIIs currently being shipped (serial numbers 0033 and above) are fully software compatible with both types of cell. Earlier models may need to be upgraded in order to work with the photometer cell.

CAIIs (serial numbers 0014 and before)

These CAIIs require both the hardware and the software upgrading. When ordering a photometer cell for an existing unit, it will be necessary to return the control unit for the hardware upgrade (free of charge).

CAIIs (serial numbers 0015 to 0032)

These CAIIs have compatible hardware but require version 4.00 software. The microprocessor card requires two EPROM sockets for version 4.00 software, some cards may require an additional socket soldering to the card. Version 4.00 software will include a spare socket to be fitted if required. We can also supply an exchange microprocessor card with the new software installed for anybody not confident in fitting the additional socket. Alternatively the control unit can be returned to us for the upgrade (free of charge).

Technical Data

Weight (photometer cell):
Size (photometer cell, excluding lead):
146mm (l) x 28mm (d)
Stainless steel with glass optical window.
Light source:
Approx. 50µl PVSK vs. Polybrene titration.
Requires version 4.00 software and above.

Ordering Information

Order Code Description
CHA101A Charge Analyzer photometer cell complete with clamp

Rank Brothers Ltd reserves the right to change specifications in the light of continuing development.

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