Introduction
Composition of ...
Main Chemicals, Compounds, Components
Sodium bicarbonate (NaHCO3), also known as baking soda or sodium hydrogen carbonate, is one of the two main parts of bath bombs. It is a slightly alkaline, white powder with a pH of 8.3 and no odor. Because this ionic compound is a weak base, it does not completely ionize in water. Baking soda forms sodium and bicarbonate ions upon separation, which buffers excess hydrogen ions and leads to a higher blood pH. The melting point is 108.8 C°, the boiling point is 851.1 C°, and the density is 2.1 g/cm³.
Citric acid (C6 H8O7) is colorless and odorless with an acidic taste due to its pH of 3.24. It is found in citrus fruits and is a key factor in metabolism. Citric acid maintains stability among ingredients, so it is used as a preservative. Pharmaceutical preparations often use citric acid because of this molecules antioxidant properties. It chelates calcium in the blood, which treats heavy metal poisoning. The melting point is 152.7 C°, the boiling/decomposing point is 310 C°, and the density is 1.665 g/cm³.
Chemistry's Role
How are Bath bombs made?
Background Research
One wonderful aspect of bath bombs is that they are chemistry that can be prepared right from the kitchen. However, combining the ingredients can be a little tricky. The wet ingredients will initiate the reaction between the baking soda and citric acid, so it is important to blend the coconut oil mix quickly with the dry mix. Once all of the ingredients are mixed thoroughly, the mixture is pressed into molds to dry. When dried, the bath bomb is complete, and will react with the warm bath water.
Upon touching the water, the citric acid + baking soda yields Sodium Citrate (Na3C6H5O7) + Water (H2O) + Carbon Dioxide (CO2). Effervescence occurs as the CO2 is produced, resulting in fizzing and foaming. The food coloring (indigotine = C16H8N2Na2O8S2) dissipates and dyes the bath water faintly. The epsom salts are dissolved by the water, and the essential oils disperse as well, leaving the water mildly fragrant and lightly tinted whatever color was used.
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About the Author
Beccah Chambers is a junior at Billings Senior High School. She enjoys all types of art, traveling, and random fun facts. She has three siblings, and spends a lot of time thinking of new and crazy ideas.