• Easier to use and more accurate than chemical test kits
• Colorimetric method
• Large, easy to read digits
• Auto shut-off
• The Checker HC easily fits into the palm of your hand or pocket
• Use for quick and accurate on the spot analysis
• Single button operation: Zero and Measure
• Operated by a single AAA battery

1. HI 755 has been developed specifically for testing alkalinity in marine water. The reagents and software are different from our fresh water test kits and meters which we have been selling for many years.
2. HI 755 uses a photometric method to determine alkalinity. This method is one of the various approved methods to measure this parameter (for example EPA method 310.2 Alkalinity Colorimetric, Automated, Methyl Orange, applicable to drinking, surface, and saline waters, domestic and industrial wastes).
3. HI 755 was developed and benchmarked versus an automatic titrator (Hanna model HI 902 with 40,000 step burette and 0.001 pH resolution) using synthetic seawater standards with different alkalinity levels, and validated with aquarium samples. The end point of the titration for seawater is slightly different from the end point for freshwater (4.2 pH vs 4.5 pH). In either case, our tests clearly showed the difference between these two points was very small. The slope at this point is high. (The actual end point varies slightly depending on the composition of the sample. For example, using Gran’s Plot we have found the endpoint to be at pH 4.375 for a particular aquarium sample).
4. HI 755 was retested to try to understand possible causes for these discrepancies. One critical component of the photometric method is to ensure the reagent is completely dissolved in the sample. During our analysis, we noticed lower readings were obtained when the reagent was not completely dissolved. We traced this back to the various shaking techniques used by our chemists. When we standardized the shake time to two minutes, all variances in shaking technique were voided and the results were consistent and accurate.

Order Information:
HI 755 Checker HC is supplied with (2) sample cuvettes with caps, (6) powder reagents for Alkalinity, (1) 1.5V AAA battery and instructions.