Wikipedia describes chlorine as... "the chemical element with atomic number 17 and symbol Cl. It is a halogen, found in the periodic table in group 17 (formerly VII, VIIa, or VIIb). As the chloride ion, which is part of common salt and other compounds, it is abundant in nature and necessary to most forms of life, including humans. In its elemental form (Cl2 or "dichlorine") under standard conditions, chlorine is a powerful oxidant and is used in bleaching and disinfectants, as well as an essential reagent in the chemical industry. As a common disinfectant, chlorine compounds are used in swimming pools to keep them clean and sanitary."

Most people assume chlorine testing only applies to pool water, but in reality, a person can find chlorine in many municipal water supplies, private wells, and in numerous manufacturing processes. Each application demands a different amount of chlorine and therefore each application requires a different testing method for chlorine concentrations.

DPD Test for Oxidizers... DPD -- The most common method for testing chlorine concentrations involves the use of a chemical known as DPD (N,N Diethyl-1,4 Phenylenediamine Sulfate) which comes in powder, tablet, reagentstrip, and liquid form. Each form of DPD has its advantages and disadvantages. The addition of DPD to water samples containing oxidizers such as free chlorine, bromine, iodine, chlorine dioxide and/or permanganate results in the formation of a reddish tint to the water whose intensity directly relates to the amount of oxidizer(s) present in the water sample. Click here for more information on DPD.

OTO Test for Oxidizers... OTO -- Commonly used in the pool & spa market for quite a long time, the addition of OTO (Orthotolidine) to water containing certain oxidizers, usually chlorine or bromine, will result in the formation of a color ranging from pale, light yellow to blood red. Although many test kits for pools and spas still pair OTO up with phenol red, a chemical used to measure pH, because of how simple the two chemicals make water testing, OTO tests only for total chlorine and provides semi-quantitative results at best. Most swimming pool and drinking water professionals agree that free chlorine levels matter much more than total chlorine levels when it comes to the sanitizing and disinfecting of water.

Water Testing and Water Quality Information... Looking for general information on water testing, water quality issues, and other topics related to the testing of water for drinking, swimming, industrial and other applications? Below you will find the most recent addition to the Water Testing Blog:    River of Blood Flowing Into the Trinity River? -- OK, so if THIS does not tell you that owners of private wells should perform periodic testing of the water pulled from their wells, then we wholeheartedly doubt we will ever find a better reason. A hobbyist drone (unmanned aircraft) pilot in the Dallas, TX area captured a rather disturbing image of what looked like [...]... 01/25/2012 | read the full article      Science Fair Project: Testing for Arsenic in Apple Juice? -- With so many news outlets discussing recent findings of arsenic in bottles of apple juice bearing brand names it comes as no surprise to us that we would receive an inquiry like the one we just got from ‘Hadiah’ who asked, “I would like to know exactly what arsenic testing kit i could use for [...]... 01/24/2012 | read the full article      Orange Hair From Tap Water? Too Much Iron in the Water! -- Can you get orange hair from tap (or well) water? Some residents in the Boulder Hill area of Illinois have presented their local water department with evidence that it can happen… and have water test results documenting the presence of three times the normal level of iron in their tap water. Last week, residents complained [...]... 01/18/2012 | read the full article      Turns Red When Mixed With Chlorinated Water — Leak Detection -- Every once in a while we get a question about a topic related to water quality, but not quite a water quality question… so today’s question came to us from ‘Michael’ who asked, I need to purchase a quick test means to locate water leaks in supply pipes to my residential water service meter. The [...]... 01/17/2012 | read the full article      Bad Water in Brooklyn? -- Many times in life we will unknowingly get exposed to potentially harmful contaminants — and never know about it. Other times we know about it and just don’t know what to do about it. Today’s inquiry came to us from a woman named ‘Rachel’ who asked, Hi..I work in an office building in brooklyn (11211) [...]... 01/15/2012 | read the full article   More Entries From WaterTestingBlog.Com