Litmus paper is used to test the pH balance of a liquid or substance. Most substances are either alkali or acid. Alkaline, or basic, chemicals include baking soda, ammonia and lye. Acidic substances include vinegar, lemon juice and battery acid. Alkalies and acids are at opposite extremes chemically, and will cancel each other out to form a neutral substance when mixed together at equal strengths.
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Blue and red litmus papers are designed to test substances at different pHs. Use blue paper to test acidic substances and red paper to test alkaline ones.
Blue Litmus Paper
When blue litmus paper is placed in a substance that is acidic, it will turn to red. However, if placed in a substance that is basic or neutral, it will remain blue. Blue litmus paper is meant to test only for an acidic pH level.
What Are Acids?
Acids are substances that have a low hydrogen potential, meaning that they will not readily bind with hydrogen molecules. Anything with a pH level of less than 7 is said to be acidic.
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Red Litmus Paper
When red litmus paper is placed into a basic substance, it will turn blue. If it comes in contact with an acidic or neutral substance, it will remain red. Red litmus paper is meant to test only for an alkaline pH level. Common acids include include tartar sauce, corn, bacon and beer.
What Are Alkalies?
Alkaline, or basic, substances are those that have a high hydrogen potential, meaning that they will readily bind with hydrogen molecules. Anything with a pH of more than 7 is basic. Common alkalies include tomatoes, almonds and molasses.