What Is Oxalic Acid Dihydrate?
Oxalic acid dihydrate is an organic compound represented by C2H2O4-2H2O.
The CAS number is 6153-56-6. It has a molecular weight of 126.07 and a melting point of 104-106°C. It is a white crystal or crystalline powder at room temperature. The compound is soluble in water and ethanol and insoluble in diethyl ether.
Oxalic acid dihydrate is hygroscopic, and therefore, when left in moist air, it will assume the dihydrate state. Dihydrate also precipitates from aqueous solutions.
Uses of Oxalic Acid Dihydrate
Oxalic acid dihydrate is mainly used in the chemical field as a reagent, metal surface treatment agent, reducing agent, and intermediate raw material for pharmaceuticals. Specific examples are the production of persistent sulfa drugs, cerium oxalate, amino acid preparations, and alpha-keto acids. Due to its reducing properties, it can also be used in reductive titrations.
The compound is also approved as a food additive. However, when used as a food additive, the oxalic acid must be removed from the final product. Examples include the manufacture of glucose syrup and the refining of vegetable oils.
Other uses include raw materials for dyes and bleaching agents, and it is widely used.
Characteristics of Oxalic Acid Dihydrate
Oxalic acid dihydrate becomes anhydrous when placed in a desiccator containing diphosphorus pentoxide or heated to 100°C. It has two carboxyl groups. It is a divalent carboxylic acid with two carboxyl groups and acts as an ionized acid in an aqueous solution.
The acid dissociation constants pKa are 1.27 and 4.27. Because of its property as a reducing agent, it is used as a primary standard in redox titration in analytical chemistry.
Types of Oxalic Acid Dihydrate
Oxalic acid dihydrate is mainly available as a reagent for research and development and as an industrial chemical. R&D reagents are available in 25g, 100g, 500g, 2.5kg, etc., and are supplied in volumes that are easy to handle in the laboratory. These reagent products can be stored at room temperature.
As industrial chemicals, they are available in large capacities that are easy to handle in factories, such as 20 kg. Main applications include metal surface treatment agents and raw materials for pharmaceutical intermediates.
Other Information on Hydroperoxides
1. Production and Synthesis of Oxalic Acid Dihydrate
Oxalic acid is abundantly contained in plants, and is the origin of its naming. Industrially, it is produced by extracting wood chips after treating them with alkali.
Oxalic acid dihydrate is hygroscopic and becomes dihydrate when left in moist air. It also precipitates from aqueous solution in the dihydrate state.
Typical synthesis methods are as follows:
- Sodium oxalate is synthesized by thermal decomposition of sodium formate, isolated as calcium oxalate using calcium hydroxide, and then decomposed with sulfuric acid.
- Method of oxidizing ethylene glycol and glyoxal with potassium dichromate, etc.
2. Oxalic Acid and Health
Oxalic acid has the property (deleterious) of strongly binding to calcium ions. When it enters the bloodstream of a living body, it is believed to form oxalates with calcium, reducing the amount of calcium available to the body and inhibiting the coagulation and coagulation action of blood. The substance is also thought to cause some stones if taken in excess.
Some vegetables, such as spinach and ginger, contain oxalic acid, but it is water soluble and can be reduced by boiling in cooking. In addition, when taken with calcium at the same time, oxalic acid combines with calcium in the intestines to form oxalates, which are less likely to be absorbed by the body.