Review on Hanna Instruments HI701 Handheld Colorimeter by Shaun Bushey

Some tools are specially limited to encourage purchase. I believe this is one of those tools. It turns out that there are multiple wavelengths and times for different measurements. The wavelength is determined by the color of the LED, and the resistance at the base of the device apparently determines the countdown time. This means that multiple parameters can be measured with a single instrument if the reagents and reaction times are right. With two cuvettes, the free chlorine tester can be used for free and total chlorine as well as other 525 nm based tests. . I've tried this with free chlorine and total chlorine tests and I think it's a great alternative to the Taylor test kits. Taylor kits (K2005 in particular) require light pinks to be matched to determine chlorine levels. Exposure to light is also not always definitive and the measurement error is around ± 0.5 ppm. This gauge gives an easy to read number. All the hassle of priming the reagent and setting the timer is eliminated if the user simply takes two samples, uses one as a control, and then manually measures the waiting time (1 minute for free chlorine, 2.5 minutes for total chlorine). Just before the time is up, place the unreacted sample, let the instrument take a baseline reading, then insert the reacted sample and let the controller do its thing. I compared the results to Taylor's test set and got relatively similar readings. The Taylor test kit I have is quite old and the reagents are long past their expiration date (which is why I bought this test). I have also used this test program with Taylor's reagents and also got relatively similar readings. I bought 100 test packs for both free and total chlorine so I'm set for a while. Please note that Hanna reagents require a pH of less than 8.2. My pH was high and I didn't get a useful reading until I lowered the pH below 8.0. This tester can also be used with other 525nm tests. I have a marine aquarium and wanted to check my phosphate/phosphorus levels. Phosphorus Reagents HI 736-25) showed 0.70 ppm. I don't have any algae issues so that seems reasonable. I recently ordered HI 713-25 phosphate reagents and will compare the readings. I also have some HI 721-25 Iron Reagents but haven't tested them yet. If anything, I might recommend a Hanna Instruments HI 711 Total Chlorine Tester for its 3.50 ppm range. HI 701 is limited to 2.50 PPM. Both have a resolution of 0.01ppm and an accuracy of ±0.03ppm.