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Roger Weller, geology instructor

by Marcus Aves
Physical Geology
Spring 2015





Everyone knows that poisons are dangerous. They can cause many problems to the human body. Poisons can eat your skin away, stop you from breathing, cause a stroke, heart attack, gallbladder problems, eat your insides out, paralyze you, and even kill you. So many people have heard of this poison Arsenic. Arsenic is periodic table number 33, it is an element. Most people know what Arsenic is.  An insecticide or weed killer or a pest control poison for rats. In this form it is a poisonous trioxide As2O3 or As4O6 of arsenic used especially as. Arsenic in its true form is defined as a trivalent and pentavalent metalloid poisonous element that is commonly metallic steel gray, crystalline, and brittle and is used especially in wood preservatives, alloys, and semiconductors. Arsenic appears in three forms yellow, black and grey. The most stable form is a silver-gray. It is brittle crystalline solid, it tarnishes rapidly in air, and at high temperatures burns forming a white cloud of arsenic trioxide.

  Sample of arsenic trisulfide as orpiment mineral          



Chemical Group:    native element
Chemical Formula:   
Color:  tin-white; tarnishes to dark gray                   

Streak:  same as color
Luster:  almost metallic

Hardness:  3.5            

Specific Gravity:  5.7                  
Fracture:  uneven to fine granular
Cleavage:  present, but rarely seen

Crystal Forms and Habits:  Rhombohedral (crystals rare) Usually granular massive
Mineral Associations: NATIVE ARSENIC (Arsenic- As), ARSENOPYRITE (Iron Arsenide Sulfide), COBALTITE (Cobalt Iron Arsenic Sulfide), ENARGITE (Copper Arsenic Sulfide), ERYTHRITE (Hydrated Cobalt Arsenate), ORPIMENT (Arsenic Sulfide), PROUSTITE (Silver Arsenic Sulfide), REALGAR (Arsenic Sulfide), and TENNANTITE (Copper Arsenic Sulfide)

Identifying Characteristics: Gray arsenic is the most common. It has a metallic sheen and conducts electricity. Yellow arsenic is metastable, is a poor electrical conductor and does not have a metallic sheen. It is prepared by cooling gray arsenic vapor in liquid air. It reverts to gray arsenic at room temperature. Black arsenic can be prepared by cooling arsenic vapor at 100oC – 200 oC. It is glassy, brittle and a poor electrical conductor.
Toxicity: when- very high, when inhaled- very high




            Arsenic comes from the Latin word arsenicum and Greek word arsenikon: yellow orpiment, identified with arenikos, male, from the belief that metals were different sexes; Arabic Az-zernikh: the orpiment from Persian zerni-zar. Arsenic was known to the ancient Egyptians, and is mentioned in one papyrus as a ways of gilding metals. The Greek philosopher Theophrastus knew of two arsenic sulfide minerals: orpiment (As2S3) and realgar (As4S4). The Chinese also knew about arsenic as the writings of Pen Ts’ao Kan-Mu. He compiled his great work on the natural world in the 1500s, during the Ming dynasty. He noted the toxicity associated with arsenic compounds and mentioned their use as pesticides in rice fields. A more dangerous form of arsenic, called white arsenic, has also been long known. This was the trioxide, As2O3, and was a by-product of copper refining. When this was mixed with olive oil and heated it yielded arsenic metal itself. The discovery of the element arsenic is attributed to Albertus Magnus in the 1200s.





Arsenic can be found naturally on earth in small concentrations. A little uncombined arsenic occurs naturally as microcrystalline masses, found in Siberia, Germany, France, Italy, Romania and in the USA. Most arsenic is found in conjunction with sulfur in minerals such as arsenopyrite (AsFeS), realgar, orpiment and enargite. Arsenic is a component that is extremely hard to convert to water-soluble or volatile products. The fact that arsenic is naturally a fairly a mobile component, basically means that large concentrations are not likely to appear on one specific site.







Map-- Arsenic concentrations in ground water




Arsenic in ground water is largely the result of minerals dissolving from weathered rocks and soils. Several types of cancer have been linked to arsenic in water. In 2001 the US Environmental Protection Agency lowered the maximum level of arsenic permitted in drinking water from 50 micrograms per liter (ug/L) to 10 ug/L. The USGS has developed maps that show where and to what extent arsenic occurs in ground water across the country. The current maps are based on samples from 31,350 wells. Widespread high concentrations were found in the West, the Midwest, and the Northeast.









            Arsenic is used as a doping agent in solid-state devices. Gallium arsenide is used in lasers which convert electricity into coherent light. Arsenic compounds, such as Paris green, calcium arsenate and lead arsenate, are used as insecticides and in other poisons. Arsenic is used in pyrotechnics to give additional color to the flame. Arsenic improves the sphericity of lead shot. Arsenic is used pyrotechny, hardening and improving the sphericity of shot, and in bronzing. Arsenic as also been used to preserve wood. It was used for desks, landscaping timbers, picnic tables, walkways/ boardwalks, gazebos, residential fencing, patios, and play structures.




Arsenic is also used in medical field and other fields as well. Very scary thing. Arsenic can be used for treating a certain type of leukemia (acute promyelocytic leukemia). A specific prescription-only intravenous medication is used for this purpose. Arsenic is used in the following things: growing food, makeup, cigarettes, poisons, water, food poisoning, insomnia, allergies, anxiety, depression, obsessive-compulsive disorder (OCD), psoriasis, syphilis, asthma, rheumatism, hemorrhoids, cough, itchy skin, and cancer. The use of Arsenic is very wide.









Arsenic is likely safe when eaten in normal food amounts. The form of arsenic found naturally in foods (organic arsenic) does not seem to cause any harm at a level of 50 mcg/L and it has been linked to reduced scores on intelligence tests in children. Also, arsenic trioxide (Trisenox) is likely safe when given intravenously (by IV) to adults by a healthcare provider. It is an FDA-approved prescription drug.



Other forms of arsenic (inorganic arsenic) are likely unsafe when taken by mouth. These forms can be very poisonous, even in small doses. Don’t take arsenic supplements. Taking 10 mcg/kg/day over a period of time can produce symptoms of arsenic poisoning. Taking 5 mg of arsenic, or sometimes less, can cause digestive tract symptoms. Higher doses can cause severe poisoning and death. Inorganic arsenic is classified as a human cancer-causing agent.


Laws have been made to regulate the amount of arsenic that is allowed in the water supply. The maximum permissible level of arsenic in drinking water is 10 mcg/L. Long-term exposure to arsenic in drinking water at a level of 50 mcg/L has been linked to reduced scores on intelligence tests in children. Long-term exposure to arsenic in drinking-water is causally related to increased risks of cancer in the skin, lungs, bladder and kidney, as well as other skin changes such as hyperkeratosis and pigmentation changes.


These effects have been demonstrated in many studies using different study designs. Exposure–response relationships and high risks have been observed for each of these end-points. The effects have been most thoroughly studied in Taiwan but there is considerable evidence from studies on populations in other countries as well. Increased risks of lung and bladder cancer and of arsenic-associated skin lesions have been reported to be associated with ingestion of drinking-water at concentrations £ 50 µg arsenic/litre.









Now you see what Arsenic is. From its different forms, its origin, where it comes from, to its uses, and the side of effects of Arsenic. Arsenic can be used for good and bad things. It all depends on the amount that you use. I hope now you understand the danger of Arsenic. Use properly and be cautious with Arsenic or this might be you.




Works Cited

U.S. Department of the Interior | U.S. Geological Survey
Photo credit to Theodore W. Gray

Photo credit to Roger Weller