pH, Free and Total Chlorine, Total Hardness, and Iron Low-Range Portable Photometer-kit

Chlorine and pH are two of the most closely monitored parameters in the analysis of water quality. The disinfecting power of a chlorine solution is pH-dependent; hypochlorous acid (HOCl) is the more effective form of chlorine that is predominant at lower pH levels. As the pH increases, the less effective hypochlorite (OCl-) form becomes more prevalent. Hardness is also an important water quality parameter as it can indicates the presence of magnesium and calcium, which are responsible for scaling of pipes in heating and cooling systems. In domestic water, iron can cause an unpleasant taste, stain laundry, or damage kitchenware; it is also an indicator of ongoing corrosion in piping systems.

The HI97745 offers multiple methods within one meter. pH determination uses the phenol red method; free and total chlorine determination uses an adaptation the Standard Method 4500-Cl G; total hardness determination uses an adaptation of the Standard Methods for the Examination of Water and Wastewater, 23rd Edition, colorimetric method; low range iron determination uses an adaptation of the TPTZ method.

The reagents are in powder or liquid form depending on the parameter being tested. When the appropriate reagent is added to the sample, it will display a color change; the greater the concentration, the deeper the color. The associated color change is then colorimetrically analyzed according to the Beer-Lambert Law. This principle states that light is absorbed by a complementary color, and the emitted radiation is dependent upon concentration. For determination of pH, free and total chlorine, total hardness, and iron, a narrow band interference filter at 525 nm allows only green light to be detected by the silicon photodetector and omits all other visible light emitted from the LED. As the change in color of the reacted sample increases, absorbance of the specific wavelength of light also increases, while transmittance decreases. Using a pre-programmed curve a result is then displayed.

The HI97745 has an innovative optical system that offers superior performance in accuracy, repeatability, and the short amount of time it takes to perform a measurement. This compact, waterproof meter is extremely user friendly with a tutorial mode that walks the user graphically, step by step, in performing a measurement. The use of a backlit dot matrix LCD allows the use of virtual keys which makes the operation of the meter very intuitive including selecting different units of measure, reviewing GLP data, recalling the last 50 measurements, and customizing the meter to user preferences.

HI97745 is completely waterproof including the cuvette holder that is designed with ridges to protect the optical path from getting scratched by the cuvette and a gasketed battery compartment that holds three common AA batteries. The compact design fits comfortably in the hand for use in the field or on a table for benchtop use. The LCD is backlit for easy viewing under all conditions.

• LED that generates very little heat


• 8 nm narrowband interference filter that is accurate to ±1 nm.


• Reference detector that modulates the voltage to LED for consistent light output.


• A concave focusing lens that reduces errors from imperfections in the cuvette.

On-Screen Features

CAL Check
Advanced features including CAL-Check to verify performance and if necessary, recalibrate.

Multiple Chemical Forms
Display hardness results in multiple chemical forms.

Setup Options
Setup options for meter personalization include date and time format, language, and enabling the tutorial mode.

Backlit Display
Backlit dot matrix LCD that offers an exceptionally intuitive user interface that is easy to read and understand.

Tutorial Mode
Tutorial mode for step-by-step instructions to guide a first-time user in how to perform a measurement correctly.

Reaction Timer
Built-in reaction timer that ensures consistency amongst multiple users.

HI97745 FEATURES/BENEFITS: