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For strong acids or bases, these values may actually be higher than 14 or lower than 0, but the 0-14 range is most commonly encountered.
These D.O.T.-required labels, signs and placards are available at Safety Emporium.
The pH values of some common substances are given in the table below.
|Substance||Typical pH||[H+], M|
|Stomach acid (gastric juices)||1.4||0.0398|
|Vinegar||3.0||1 x 10-3|
|Tomatoes||4.2||6.31 x 10-5|
|Water exposed to air||5.5||3.16 x 10-6|
|Pure water||7.0||1 x 10-7|
|Blood or tears||7.4||3.98 x 10-8|
|Baking soda||8.4||3.98 x 10-9|
|Household ammonia||11.5||3.16 x 10-12|
|Household bleach||12.5||6.31 x 10-13|
pH can be measured in many different ways. A simple example is litmus paper which can tell you if a solution is basic or acidic. Other fast and inexpensive indicator papers and reagents can also be used. Examples include phenolphthalein, bromophenol blue, methyl red and gentian violet (see Further Reading below for more). Electronic pH meters can provide very accurate pH determinations over a wide range of hydrogen ion concentrations, but cost more than simple indicators.
Finally, note that the concept of pH is technically/generally correct only for dilute solutions (say, 0.001 M and below). As the concentration of a dissolved substance, in this case, H+ becomes greater, chemists use a concept called activity instead. This is because ions have charge, and when there are enough ions in the solution, they begin to interact in ways that may affect their availability to interact with other species. But for the purposes that most of need on an MSDS, pH works just fine.
pH is also important to know in case you spill the material on your skin or eyes. Whenever a substance enters the eye, flush with water for 15 minutes and get prompt medical attention. If a basic substance enters the eye this is particularly important as basic materials tend to cause worse eye damage and are harder to flush out of the eye tissues than acidic materials.
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