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Acid Bottle Selection
The type of bottle selected for dispensing the acid is important. Laboratory supply stores sell bottles that are designed for dispensing acid one-drop-at-a-time. The lid is always on these bottles (except when they are being cleaned or refilled), and they do not produce a spill when they are knocked over. Bottles with a removable lid…
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Limiting Frivolous Acid Use in Labs
Most students are intrigued with the acid test and want to try it. To limit frivolous acid use, students should be instructed to use a single drop of acid for the test and to only test specimens when carbonate minerals are suspected. If that is not done, some students will use the acid frivolously. This…
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Contamination in Mineral Identification Labs
When students are given minerals to identify, two situations can cause problems with their work. 1) In mineral identification labs, some students are ready to call any mineral that produces an acid reaction “calcite” or another carbonate. However, calcite is a ubiquitous mineral and it is often present as an intimate part of other mineral…
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The Acid Test on Rocks
LIMESTONE, DOLOSTONE, AND MARBLE Some rocks contain carbonate minerals, and the acid test can be used to help identify them. Limestone is composed almost entirely of calcite and will produce a vigorous fizz with a drop of hydrochloric acid. Dolostone is a rock composed of almost entirely of dolomite. It will produce a very weak fizz when a drop of cold…
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The Vigor of Carbonate Reactions
Careful observation is important because some carbonate minerals react vigorously and others barely react with cold acid. The carbonate mineral that is most commonly encountered by geologists is calcite (CaCO3). Calcite is a “ubiquitous” mineral. Ubiquitous means “found everywhere.” Calcite occurs in igneous, metamorphic, and sedimentary rocks and is the most commonly encountered carbonate mineral. If you place one…
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What Causes the Fizz?
Carbonate minerals are unstable in contact with hydrochloric acid. When acid begins to effervesce (fizz) on a specimen, a reaction similar to the one shown below is taking place. On the left side of this reaction, the mineral calcite (CaCO3) is in contact with hydrochloric acid (HCl). These react to form carbon dioxide gas (CO2),…
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What is the Acid Test?
To most geologists, the term “acid test” means placing a drop of dilute (5% to 10%) hydrochloric acid on a rock or mineral and watching for bubbles of carbon dioxide gas to be released. The bubbles signal the presence of carbonate minerals such as calcite, dolomite, or one of the minerals listed in Table 1. The bubbling…
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How Did They Do That?
The next time you go to a Fourth of July fireworks display, study the different types of bursts and imagine how they might have been accomplished. You can probably imagine how many of them are done.
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The Mechanics of an Aerial Fireworks Burst
The people who make fireworks are really clever. They combine a knowledge of chemistry and physics with artistic ingenuity to produce an infinite variety of fireworks bursts. How do they do it? They change the size, shape, density, composition and placement of the stars within the fireworks shell. By doing this they change the shape,…
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What Causes the Colors?
Chemistry holds the secrets to the color of a fireworks burst. The colors that you see in the sky are determined by metallic compounds that are deliberately added in very small amounts to the stars when they are manufactured. As the stars burn, the metal atoms absorb energy, become excited and emit a specific color…