CALCIUM ARSENATE

Description

The calcium arsenate that is sold commercially today as an insecticide is not a single chemical compound but a complex mixture of several calcium arsenates and an excess of calcium hydroxide. The material is made from arsenic trioxide by first oxidizing it to arsenic pentoxide with nitric acid and then reacting the solution of arsenic pentoxide or arsenic acid with a slurry of calcium hydroxide. The conditions of temperature,concentration, and duration of reaction are important because of their influence on the physical nature of the product.

Chemical properties

White powder. Slightly soluble in water; soluble in dilute acids. Decomposes on heating.

Physical properties

Commercial calcium arsenate generally is colored pink and is alkaline in reaction. It is a finely divided powder.

The Uses of CALCIUM ARSENATE

Calcium arsenate has been used extensively against certain insects affecting field crops, especially cotton. It cannot be used safely on apples, peaches, beans, and some other crops because of its burning effect on the foliage and fruit. It is banned by a number of countries.

The Uses of CALCIUM ARSENATE

Insecticide; molluscicide.

The Uses of CALCIUM ARSENATE

Calcium arsenate is also used in weather- resistant wood treatment. It was used mainly in viticulture, in the past. it was mainly used against the boll weevil in cotton cultivation.

Preparation

An old method involving electrolysis in solution for the manufacture of calcium arsenate is as follows. A solution of arsenious oxide in caustic soda (As₂O₃:NaOH=198:250) is electrolyzed between iron electrodes. Hydrogen and a small quantity of metallic arsenic are liberated at the cathode and very little oxygen at the anode, the basic arsenite in solution being oxidized to arsenate. When this oxidation is complete, any arsenic is filtered off and the solution treated with milk of lime. A basic arsenate of extremely low solubility is precipitated and after removal, is washed and dried.

Definition

ChEBI: Calcium arsenate is a polymer.

General Description

White powder. Slightly soluble in water. Toxic by inhalation and ingestion. Used as an insecticide and germicide.

Air & Water Reactions

Slightly soluble in water.

Reactivity Profile

Has only weak oxidizing power but redox reactions can still occur. Soluble in dilute acids. [Hawley]. Produces toxic fumes of arsenic when heated to decomposition .

Hazard

Toxic by ingestion and inhalation.

Health Hazard

CALCIUM ARSENATE is extremely toxic; the probable oral lethal dose for humans is 5-50 mg/kg, or between 7 drops and 1 teaspoonful for a 150 lb. person. It is an irritant to eyes, respiratory tract, mouth and stomach. Damage to kidneys, liver and the nervous system have been reported. (Non-Specific -- Arsenic) Chronic exposure can cause bone marrow damage, often leading to aplastic anemia. There is epidemiological evidence that chronic ingestion of arsenic compounds causes a predisposition to skin cancers.

Fire Hazard

Fire may produce irritating or poisonous gases. When heated to decomposition, CALCIUM ARSENATE produces toxic fumes of arsenic. Avoid heat. Hazardous polymerization may not occur.

Safety Profile

Confirmed human carcinogen. Poison by ingestion. Moderately toxic by skin contact. When heated to decomposition it emits toxic fumes of arsenic.

Potential Exposure

AgriculturalChemical Tumorigen. Workers engaged in manufacture,formulation, and application of pesticides containing calcium arsenate.

First aid

If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least15 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts theskin, remove contaminated clothing and wash immediatelywith soap and water. Seek medical attention immediately. Ifthis chemical has been inhaled, remove from exposure,begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR ifheart action has stopped. Transfer promptly to a medicalfacility. When this chemical has been swallowed, getmedical attention. Give large quantities of water and inducevomiting. Do not make an unconscious person vomit.Medical observation is recommended for 24-48 h afterbreathing overexposure.Note to physician: For severe poisoning BAL [BritishAnti-Lewisite, dimercaprol, dithiopropanol (C3H8OS2)] hasbeen used to treat toxic symptoms of certain heavy metalspoisoning including arsenic. Although BAL is reported tohave a large margin of safety, caution must be exercised,because toxic effects may be caused by excessive dosage.Most can be prevented by premedication with 1-ephedrinesulfate (CAS: 134-72-5). For milder poisoning penicillamine(not penicillin) has been used, both with mixed success.Side effects occur with such treatment and it is never a substitute for controlling exposure. It can only be done understrict medical care.

storage

Color Code—Blue: Health Hazard/Poison: Storein a secure poison location. Prior to working with Calciumarsenate you should be trained on its proper handling andstorage. Store in tightly closed containers in a cool, wellventilated area. A regulated, marked area should be established where this chemical is handled, used, or stored incompliance with OSHA Standard 1910.1045.

Shipping

The DOT label requirement is “POISONOUS/TOXIC MATERIALS.” The Hazard Class is 6.1 and thePacking Group is II.

Incompatibilities

None reported, according to NIOSH.When heated produces arsenic fumes.