Dry ice is the solid form of carbon dioxide (CO2), an extremely cold substance with a surface temperature of approximately \(-109.2^\circ \text{F}\) (\(-78.5^\circ \text{C}\)). Unlike water ice, it does not melt into a liquid; instead, it undergoes sublimation, turning directly into a gas. This property makes it a highly effective, mess-free cooling agent for preserving perishable goods and medical samples. It is also commonly used to produce dense, low-lying fog effects for entertainment.
Where to Find Dry Ice
The most common sources for purchasing dry ice are large chain grocery stores and supermarkets. Major national retailers often stock it in dedicated freezer chests, usually located near the front of the store or the frozen goods section. Availability can be seasonal, being more reliable during holidays or warmer months. It is wise to call the store ahead of time to confirm their current supply.
Specialty retailers, such as dedicated ice companies or independent ice cream shops, may also carry dry ice for public sale. These specialized locations might be more consistent suppliers compared to grocery chains that stock it periodically. Some hardware and big-box stores also offer dry ice, particularly when demand is high.
For those needing dry ice in larger quantities, industrial gas suppliers or welding supply stores are reliable sources. Companies that handle gases often produce and sell dry ice in bulk, typically in blocks or pellets. While these suppliers cater to commercial clients, many will sell smaller amounts to the general public. Finding a supplier close to the point of use is best, as the product sublimates continuously and loses mass rapidly.
Essential Considerations Before Buying
Dry ice is generally sold by weight, typically in blocks or pellets, with retail prices ranging from \(\\)1.00$ to \(\\)3.00$ per pound. Purchasing larger quantities often results in a lower cost per unit, as many suppliers offer bulk discounts. Blocks generally last longer than smaller pellets.
Before heading to a store, you must bring a suitable container for transport, as the retailer may not provide one. The container needs to be insulated, such as a Styrofoam or thick plastic cooler, to slow down sublimation. Crucially, the container must not be airtight; it requires a vent or a slightly opened lid to allow the carbon dioxide gas to escape.
Sealing dry ice in an airtight container is extremely dangerous, as the pressure buildup from the sublimating gas can cause the container to rupture or explode. While most general retailers sell small quantities, industrial suppliers may enforce a minimum purchase requirement for walk-in customers. Some sellers also enforce an age restriction, requiring the buyer to be 18 years or older.
Safety Guidelines for Transport and Storage
The extreme temperature of dry ice can cause severe frostbite upon direct contact with skin, similar to a burn injury. For this reason, you should always use heavy, insulated gloves or tongs when handling the solid CO2. Even brief contact with bare skin must be avoided to prevent tissue damage.
When transporting dry ice in a vehicle, proper ventilation is necessary because the sublimating gas displaces oxygen in the air. The accumulating carbon dioxide gas can pose an asphyxiation risk in confined spaces like a passenger cabin or a sealed trunk. It is recommended to transport the insulated container in the trunk and keep the car windows slightly open for continuous fresh air circulation.
Dry ice should be stored in a well-ventilated area, away from children and pets, and never in a freezer. Standard freezers are not cold enough to maintain the solid form and are too airtight, which can lead to a dangerous buildup of CO2 gas. The solid should be allowed to sublimate naturally in a safe location, such as a well-ventilated garage or outdoors. Never attempt to dispose of leftover dry ice by flushing it down a toilet or sink, as the extreme cold can damage plumbing fixtures and pipes.