Oxalic acid dihydrate Chemical Properties

Melting point:

104-106 °C(lit.)

Boiling point:

108-109°C

bulk density

813kg/m3

Density 

1,65 g/cm³

vapor density 

4.4 (vs air)

vapor pressure 

<0.01 mm Hg ( 20 °C)

Flash point:

157°C

storage temp. 

Store at +5°C to +30°C.

solubility 

H2O: soluble1M at 20°C, clear, colorless

form 

Powder/Solid

Specific Gravity

1.65

color 

Yellow to yellow-green

PH

~1.0 (25℃, 1M in H2O)

PH Range

6 - 8 at 25 °C

Water Solubility 

138 g/L (20 ºC)

Sublimation 

157 ºC

Merck 

14,6911

BRN 

3679436

Exposure limits

TLV-TWA for anhydrous acid 1 mg/m³ (ACGIH, MSHA, and OSHA); TLV-STEL 2 mg/m³ (ACGIH).

Stability:

Stable. Incompatible with bases, acid chlorides, steel, silver, silver compounds, moisture. Avoid contact with metals.

InChIKey

GEVPUGOOGXGPIO-UHFFFAOYSA-N

CAS DataBase Reference

6153-56-6(CAS DataBase Reference)

NIST Chemistry Reference

Oxalic acid dihydrate(6153-56-6)

EPA Substance Registry System

Oxalic acid dihydrate (6153-56-6)

Absorption

cut-off at 303nm in H2O at 1M

Safety Information

Hazard Codes 

Xn,C

Risk Statements 

21/22-41

Safety Statements 

24/25-39-37-36-26

RIDADR 

UN 3261 8/PG 3

WGK Germany 

1

RTECS 

RO2450000

TSCA 

Yes

HazardClass 

8

PackingGroup 

III

HS Code 

29171100

Toxicity

LD50 orally in Rabbit: 375 mg/kg

MSDS

• Language:English Provider:Ethanedionic acid
• Language:English Provider:SigmaAldrich
• Language:English Provider:ACROS
• Language:English Provider:ALFA

Oxalic acid dihydrate Usage And Synthesis

Chemical Properties

white crystals

Uses

A diprotic reducing agent used as a buffer.

Uses

Oxalic acid occurs in the cell sap of Oxalisand Rumex species of plants as the potassium and calcium salt. It is the metabolicproduct of many molds (Merck 1989). Thereare a large number of applications of thiscompound, including indigo dyeing; calicoprinting; removal of paint, rust, and inkstains; metal polishing; bleaching leather; inpesticide compositions and manufacture ofoxalates. It is also used as an analyticalreagent and as a reducing agent in organicsynthesis.
Addition of oxalic acid to chromic acid forthe anodizing of Al alloy has been reported tomodify the morphology and improve the corrosion performance of anodic films (Moutarlier et al. 2004). Also, it is a very effectiveadditive for the ozone treatment of cellulose.It prevents the degradation of cellulose fromozone bleaching.

Uses

Oxalic acid dihydrate is a purifying agent in pharmaceutical industry, special in antibiotic medication, such as Oxytetracycline , Chloramphenicol , etc; * Precipitating agent in Rare-earth mineral processing; * Bleaching agent in the textile activities, wood pulp bleaching; * Rust-remover for Metal treatment; * Grinding agent, such as Marble polishing; * Waste water treatment, removing calcium from water.

Definition

Oxalic acid dihydrate (OAD) which has very high initial phase transition enthalpy is a promising phase change material (PCM). This compound is low manufacturing cost and wide usage. In OAD, alternating acid and water molecules that act both as hydrogen-bond donors and acceptors. OAD needs a lot of energy to break the hydrogen-bond in the melting process. Therefore, OAD has a very high heat of fusion of 370 J·g-1,which is a very promising PCM in TES for applications such as industrial waste heat recovery or solar energy storage systems[1].

General Description

Oxalic acid dihydrate (OAD) crystals are reported to be monoclinic with P2₁/n space group. The electron density of OAD has been obtained using X-ray diffraction studies under high resolution.

Reactivity Profile

At high temperatures oxalic acid decomposes, producing toxic carbon monoxide, andformic acid. Mixing with warm sulfuric acidmay produce the same products: CO2, CO,and formic acid. It reacts with many silvercompounds, forming explosive silver oxalate(NFPA 1986). An explosion occurred whenwater was added to an oxalic acid/sodiumchlorite mixture in a stainless steel beaker.There was also evolution of highly toxicchlorine dioxide gas (MCA 1962). Oxalicacid reacts violently with strong oxidizingsubstances.

Health Hazard

Oxalic acid is a strong poison. The toxicsymptoms from ingestion include vomiting, diarrhea, and severe gastrointestinaldisorder, renal damage, shock, convulsions,and coma. Death may result from cardiovascular collapse. The toxicity arises asoxalic acid reacts with calcium in the tissuesto form calcium oxalate, thereby upsettingthe calcium/potassium ratio (ACGIH 1986).Deposition of oxalates in the kidney tubulesmay result in kidney damage (Hodgson et al.1988).
Oxalic acid may be absorbed into the bodythrough skin contact. It is corrosive to theskin and eyes, producing burns. Dilute solutions of 10% strength may be a mild irritantto human skin. However, the inhalation toxicity is low because of its low vapor pressure.Airborne dusts can produce eyeburn and irritation of the respiratory tract.
LD50 value, oral (rats): 375 mg/kg.

Synthesis

General procedure for the synthesis of oxalic acid dihydrate from sodium oxalate: Example 1; Using an excess of HCl; 105.0 g of deionized water was added to a glass reactor. Subsequently, 100.0 g of 37% hydrochloric acid and 33.5 g of Aldrich sodium oxalate were added to the reactor. The molar ratio of hydrochloric acid to sodium oxalate was 4:1 and the molar ratio of water to sodium oxalate was 37.3:1. The mixture was placed on a hot plate at 80°C with continuous stirring for 60 minutes until a colorless, clear solution was formed and the solid was completely dissolved. Upon completion of the reaction, the reactor was transferred to an ice bath and cooled until both the internal and external temperatures were reduced to 2 °C. At this point, a white solid was precipitated from the solution. The solids were filtered using a 500 mL cellulose acetate filter funnel with a pore size of 0.45 µm. The solid was washed twice with saturated aqueous oxalic acid solution (about 50 mL each time), and the total mass of the colorless filtrate collected was 188.5 g. The solid was then washed with saturated aqueous oxalic acid solution. The solid was dried in a vacuum oven at 75°C overnight. It was confirmed by X-ray diffraction analysis (using a PANalytical X'PERT Model 3040 Automated Powder Diffractometer, Natick, MA) that the solid contained 17.8 g of oxalic acid dihydrate mixed with anhydrous oxalic acid, where the absence of crystals was an artifact of the drying process. Figure 5 illustrates the X-ray diffraction pattern of the isolated solid. Accordingly, the yield of oxalic acid dihydrate was calculated to be between 56% and 79%. Example 2; Using an insufficient amount of HCl; 130.0 g of deionized water was added to a glass reactor. Subsequently, 75.0 g of 37% hydrochloric acid and 33.5 g of Aldrich sodium oxalate were added to the reactor. The molar ratio of hydrochloric acid to sodium oxalate was 3:1 and the molar ratio of water to sodium oxalate was 39.4:1. The mixture was placed on a hot plate at 80 °C with continuous stirring for 60 minutes until a colorless, clear solution was formed and the solid was completely dissolved. Upon completion of the reaction, the reactor was transferred to an ice bath and cooled until both the internal and external temperatures were reduced to 2 °C. At this point, a white solid was precipitated from the solution. The solids were filtered using a 500 mL cellulose acetate filter funnel with a 0.45 micron pore size. The solids were washed with deionized water and the total mass of the collected colorless filtrate was 224.7 g. The solid was washed with deionized water. The solid was dried overnight at room temperature under nitrogen protection. The solid was confirmed to be 25.6 g of sodium hydrogen oxalate monohydrate by X-ray diffraction analysis (using a PANalytical X'PERT Model 3040 automated powder diffractometer, Natick, MA). Figure 6 illustrates the X-ray diffraction pattern of the isolated solid.

Purification Methods

Crystallise oxalic acid from distilled water. Dry it in a vacuum over H2SO4. The anhydrous acid can be obtained by drying at 100o overnight. [Beilstein 2 IV 1819.]

Structure and conformation

The dihydrate H₂C₂O 4·2H₂O has space group C⁵_2h–P2_1/n, with lattice parameters a = 611.9 pm, b = 360.7 pm, c = 1205.7 pm, β = 106°19′, Z = 2. The main inter-atomic distances are: C-C 153 pm, C-O₁ 129 pm, C-O₂ 119 pm. In theory, oxalic acid dihydrate is one of the very few crystalline substances that exhibit negative area compressibility. Namely, when subjected to isotropic tension stress (negative pressure), the a and c lattice parameters increase as the stress decreases from -1.17? to -0.12 GPa and from -1.17 to -0.51 GPa, respectively.

References

[1] Han, Lipeng , S. Xie , and J. Sun . "Preparation and thermal characterization of oxalic acid dihydrate/bentonite composite as shape-stabilized phase change materials for thermal energy storage." IUMRS International Conference in Asia 2017.

Oxalic acid dihydrate(6153-56-6)Related Product Information

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