Oxalic acid dihydrate Property

Melting point:

104-106 °C(lit.)

Boiling point:

108-109°C

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)

Safety

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

Hazard and Precautionary Statements (GHS)

Symbol(GHS)

Signal word

Danger

Hazard statements

H318Causes serious eye damage

Precautionary statements

P264Wash hands thoroughly after handling.

P264Wash skin thouroughly after handling.

P270Do not eat, drink or smoke when using this product.

P280Wear protective gloves/protective clothing/eye protection/face protection.

P301+P312IF SWALLOWED: call a POISON CENTER or doctor/physician IF you feel unwell.

P305+P351+P338IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continuerinsing.

Oxalic acid dihydrate Chemical Properties,Usage,Production

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.

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.