Foxcroft Equipment & Service Company's Amperometric Chlorine Analyzer's residual reading is determined by measuring the amperage produced by oxidized chlorine in the measuring cell. The amperage level is directly proportional to the level of free chlorine available in the sample stream. When reading total chlorine, the unit is actually reading converted free iodine from potassium iodine that is added to the cell for Total Chlorine readings.The cell itself is constructed such that the sample that runs through it does so at a continuous and fixed rate. Any additional flow is allowed to overflow to waste from a drain below the overflow weir. The sample stream runs down though the lower block, where it mixes with vinegar (and Potassium iodide where Total Chlorine is being analyzed), and then flows upward into the measuring cell. Within the cell, the vinegar provides pH buffering to a value of 4.0, and aids in keeping the cell clean. If Potassium Iodide is being used to read Total Chlorine, it chemically converts any free and combined chlorine residuals into free iodine, which is then read as a total chlorine reading. The cell utilizes a mixer and 150 pvc balls to ensure even chemical mix, clean the electrode and consistent readings. Very pure grades of gold and copper are used in the construction of the electrodes to enhance signal strength. Sample flow leaves the cell from the top and runs out a secondary drain to waste.
See part II to follow
1. It Optimizes Chlorine Residual Readings
A true on-line, amperometric, chlorine residual analyzer requires a pH buffer to bring the sample pH down to a range where optimum free chlorine residuals can be accurately measured, ideally 4.0 to 4.5 pH.
Any amperometric chlorine residual analyzer that claims buffers are not required uses either a pH buffered electrolyte in the probe, or makes an electronically simulated pH compensation (which is not a true chlorine residual reading).
The vinegar reduces the pH in the sampling cell, which provides the current potential needed to measure chlorine residuals accurately. Through dissociation, chlorine will be in the measurable form of hypochlorous acid rather than in its ionic state that can't be measured.
2. DPD Is Toxic, Vinegar Is Better For Our Water & Your Budget
Toxic DPD discharged to waste from one colorimetric chlorine analyzer may not seem like much; until we consider the thousands of colorimeters in service throughout the country.
The impact of toxic DPD discharge is being examined. Minimizing the use of toxic reagents could become even more important as water reuse and recycling increases.
Our contribution is to use a buffer solution, or reagent, that we all consume regularly in various foods. Distilled white vinegar is a food product, and as such doesn't require special haz mat permits or disposal, which is good for your budget and our environment.
3. Do The Math, It's Less Costly
Some chlorine analyzers require expensive, proprietary pH buffer solutions or reagents. In most parts of the country distilled white vinegar costs less than $2.50 per gallon. This means the monthly reagent cost for an FX-1000P measuring free chlorine is roughly the same price as a large pizza with extra toppings.
4. Cleanliness Is Next To Godliness
This proverb traditionally refers to personal hygiene, but it also applies to the measuring cell of our chlorine analyzer. The vinegar enhances the action of the cleaning balls in the measuring cell. It works to dissolve grease, iron, manganese, dirt and other solids. Cleanliness provides more accurate readings. It also prevents the electrodes from becoming insulated by precipitates or contaminants.
5. In A Pinch It's Readily Available
It seems like things usually break or run out after normal business hours. If your Foxcroft chlorine analyzer runs out of buffer solution at 8 PM Friday night you don't need to take grab samples over the weekend. You can pick up more "buffer solution" at a 24 hour grocery store, convenience store, or in a pinch, from your own kitchen.