Unknown Chemical
The type and condition of a chemical’s container off er clues as to the identity of its contents. Chemicals are often sold in distinctive containers. For example, clear glass bottles with color-coded caps suggest acids or ammonium hydroxide, brown bottles suggest organic solvents, steel cans with screw tops often contain ethyl ether, and so on. Even the size of the container can provide a hint as to its contents; large containers generally contain common reagents or solvents.
Lecture Bottles: To identify an unlabeled cylinder of compressed gas, contact the manufacturer, if known. If not known, request the assistance of the Environmental Health and Safety Department of a university. Do not depend upon the color of the cylinder, as color-coding is not standardized.
More Examples:
A plastic bottle that has swollen or even been split by pressure from its contents probably contains a material that has reacted with air or water, such as anhydrous calcium oxide.
Old containers of sodium or potassium hydroxide often have formed a “crown” of carbonate salts around their lids. Caps on bottles of hydrochloric acid and ammonium hydroxide will, if stored in proximity to one another, form a “wig” of ammonium chloride crystals.
If a container has even a fragment of a label still on it, you may be able to glean enough information to identify its contents or at least narrow the possibilities. Perhaps the partial label indicates part of a name, molecular weight, boiling or melting point, warning statements, or even the antidote; all these are valuable clues.
Often unknowns are in volumetric or Erlenmeyer fl asks or in beakers. Volumetric fl asks usually contain standard solutions, commonly an acid, base or buff er. If the fl ask has been covered in aluminum foil, its contents are probably a light-sensitive compound, such as silver nitrate. Liquids in small dropper bottles are likely to be test solutions or indicators. Very often, some bottles are labeled while others are not; the appearance and characteristics of the contents of the labeled ones will help identify those that are unlabelled.
WARNING! While the crystals in the examples above are harmless, crystals around the cap or inside a bottle of certain solvents could be extremely dangerous peroxides. Do not open or even touch a container of one of these chemicals or of an unknown solvent if such crystals are visible.
Lecture Bottles: To identify an unlabeled cylinder of compressed gas, contact the manufacturer, if known. If not known, request the assistance of the Environmental Health and Safety Department of a university. Do not depend upon the color of the cylinder, as color-coding is not standardized.
More Examples:
A plastic bottle that has swollen or even been split by pressure from its contents probably contains a material that has reacted with air or water, such as anhydrous calcium oxide.
Old containers of sodium or potassium hydroxide often have formed a “crown” of carbonate salts around their lids. Caps on bottles of hydrochloric acid and ammonium hydroxide will, if stored in proximity to one another, form a “wig” of ammonium chloride crystals.
If a container has even a fragment of a label still on it, you may be able to glean enough information to identify its contents or at least narrow the possibilities. Perhaps the partial label indicates part of a name, molecular weight, boiling or melting point, warning statements, or even the antidote; all these are valuable clues.
Often unknowns are in volumetric or Erlenmeyer fl asks or in beakers. Volumetric fl asks usually contain standard solutions, commonly an acid, base or buff er. If the fl ask has been covered in aluminum foil, its contents are probably a light-sensitive compound, such as silver nitrate. Liquids in small dropper bottles are likely to be test solutions or indicators. Very often, some bottles are labeled while others are not; the appearance and characteristics of the contents of the labeled ones will help identify those that are unlabelled.
WARNING! While the crystals in the examples above are harmless, crystals around the cap or inside a bottle of certain solvents could be extremely dangerous peroxides. Do not open or even touch a container of one of these chemicals or of an unknown solvent if such crystals are visible.