Chemical Education Today
CLIP, Chemical Laboratory Information Profile “Only when you know the hazards, can you take the necessary precautionary measures.”
Potassium
K
Physical Properties
Silver-white, soft metal that tarnishes when exposed to moist air Vapor pressure at 20 °C: negligible Melting point: 64 °C Boiling point: 774 °C
CAS No.: 7440-09-7 Exposure Limits OSHA PEL: ACGIH TLV:
NE NE
Hazardous Characteristics Overall Flamma- Destructive Absorbed Sensi- Self- toxicity bility to skin/eye through skin? tizer? reactive? 4 3 4 No No No
Incompatible with: Water, acetylene, alcohols, carbon, carbon disulfide, halocarbons, halogens, hydrazine, hydrogen halides, metal and non-metal halides and oxides, nitric acid, sulfuric acid, other oxidizing agents, selenium, tellurium, sulfur*
0: None (or very low); 1: Slight; 2: Moderate; 3: High; 4: Severe. *Reactivity Hazards
The reaction with water is violent and usually causes the ignition and/or explosion of the evolving hydrogen. Large chunks of potassium react with even more vigor when tossed into a body of water. Reactions with the other incompatible substances listed are also violent and dramatic. See Bretherick’s Handbook of R eactive Chemical Hazards for details and for other incompatibilities.
Cited as known to be or reasonably anticipated to be carcinogenic in NTP-11? No
Identified as a reproductive toxin in Frazier and Hage, Reproductive Hazards of the Workplace? No
Typical symptoms of acute exposures:
On the skin, inflammation, deep severe burns usually without immediate pain. If ingested, severe mouth, throat, and gastric discomfort. Principal target organ(s) or system(s):
Skin
Storage Requirements
Store in a cool, dry, well ventilated and locked location that is NOT protected by a water sprinkling system. Store potassium by immersion in dried xylene in a sealed glass container that is itself placed in a leak-proof outer container NOT made of aluminum. The quantity of xylene should be sufficient to keep the potassium immersed if the inner glass container is broken. Inspect stored potassium at least once every month to ensure its integrity. Potassium that has become coated with a yellow to orange coating (KO2) should be destroyed, not stored; see Bretherick for recommended procedures.
Additional Remarks When potassium is cut with a knife, the coating of potassium super oxide, KO2, if present on the potassium, usually explodes when forced by the cutting knife into intimate contact with the liquid hydrocarbon in which the potassium has been immersed.
Notes ReadMe
This Chemical Laboratory Information Profile is not a Material Safety Data Sheet. It is a brief summary for teachers and their students that describes some of the hazards of this chemical as it is typically used in laboratories. On the basis of your knowledge of these hazards and before using or handling this chemical, you need to select the precautions and first-aid procedures to be followed. For that information as well as for other useful information, refer to Material Safety Data Sheets, container labels, and references in the scientific literature that pertain to this chemical. Reproductive toxins
Some substances that in fact are reproductive toxins are not yet recognized as such. For the best readily available and up-to-date information, refer to “DART/ETIC”. See the TOXNET home page at http://toxnet.nlm.nih.gov/. Note that some of the data in DART/ETIC have not been peer-reviewed. See also Frazier, Linda M.; Hage, Marvin L. Reproductive Hazards of the Workplace; Wiley: New York, 1998; and Shepard, T. H. Catalog of Teratogenic Agents, 9th ed.; Johns Hopkins University Press: Baltimore, MD, 1998. Abbreviations
ACGIH TLV—American Conference of Governmental Industrial Hygienists–Threshold Limit Value. C—Ceiling. CAS—Chemical Abstracts Service. mg/m3—milligrams per cubic meter. NA—Not applicable. NE—Not established. NI—No information. NTP‑11—National Toxicology Program, Eleventh Annual Report on Carcinogens. OSHA PEL—Occupational Safety and Health Administration– Permissible Exposure Limit. ppm—parts per million. STEL/C—Short-term exposure limit and ceiling. Prepared by: Jay A. Young
Date of preparation: July 7, 2009
© Division of Chemical Education • www.JCE.DivCHED.org • Vol. 86 No. 10 October 2009 • Journal of Chemical Education
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