:Lead(II) oxalate
{{Chembox
|ImageFile = Lead(II) oxalate.svg
|ImageSize = 150
|Section1={{Chembox Identifiers
|CASNo = 814-93-7
|CASNo_Ref = {{cascite|correct|CAS}}
|UNII_Ref = {{fdacite|correct|FDA}}
|UNII = 642NGP7E5U
|PubChem =61218
|ChemSpiderID =55161
|EC_number = 212-413-5
|UNNumber = 2291
|SMILES = C(=O)(C(=O)[O-])[O-].[Pb+2]
|InChI = 1S/C2H2O4.Pb/c3-1(4)2(5)6;/h(H,3,4)(H,5,6);/q;+2/p-2
}}
|Section2={{Chembox Properties
|Formula =PbC2O4
|MolarMass =295.219
|Appearance =White Powder
|Density =5.28 g/cm3
|MeltingPtC = 327.4
|BoilingPtC = 1740
|Solubility = 0.0091 g/100 ml (25 °C)
}}
|Section3={{Chembox Thermochemistry
|DeltaHf = −851.444 kJ/mol
|Entropy = 146.0216 J "Lead(II) Oxalate". Chemistry Reference. http://www.chemistry-reference.com/q_compounds.asp?CAS=814-93-7.
}}
|Section4={{Chembox Hazards
|MainHazards =Nephrotoxin, Reproductive Toxin, Neurotoxin, IARC Carcinogen, Birth Defects, Highly Toxic
|GHSPictograms = {{GHS07}}{{GHS08}}{{GHS09}}
|GHSSignalWord = Danger
|HPhrases = {{H-phrases|302|332|360|373|410}}
|PPhrases = {{P-phrases|201|202|260|261|264|270|271|273|281|301+312|304+312|304+340|308+313|312|314|330|391|405|501}}
|PEL = 0.05 mg/m3, as Pb}}
}}
Lead(II) oxalate is an organic compound with the formula PbC2O4. It is naturally found as a heavy white solid."Lead Oxalate". American Elements: The World's Manufacturer of Engineered & Advanced Materials http://www.americanelements.com/pboxl.html.
Preparation
This compound is commercially available. It may be prepared by the metathesis reaction between lead(II) nitrate and sodium oxalate:{{cite journal | author = Grases, F. | title = Studies on Lead Oxalate Crystalline Growth | doi = 10.1006/jcis.1993.1035 | journal = Journal of Colloid and Interface Science | volume = 155 | pages = 265–270 | year = 1993 | last2 = Ruiz | first2 = J. | last3 = Costa-Bauzá | first3 = A. | issue = 2}}
:Pb2+(aq) + C2O42− → PbC2O4 (s)
A dihydrate may be formed with water solutions. But the dihydrate dehydrates in air:
:(PbC2O4•2H2O (s) → (PbC2O4 (s) + 2H2O (g)
The trihydrate (PbC2O4•3H2O) can be made by reacting a solution of lead(II) carbonate in perchloric acid with oxalylhydroxamic acid.
Properties
As well as an anhydrous form, a monohydrate (PbC2O4•H2O), a dihydrate (PbC2O4•2H2O) and a trihydrate (PbC2O4•3H2O) are known. The dihydrate is from the orthorhombic crystal system, with space group Pnam (number 62), with unit cell dimensions: a = 9.053 Å b = 8.036 Å and c = 7.834 Å. The unit cell volume is 569.8 Å3 with four formula per cell, giving a density of 3.860 g/cm3{{cite journal |last1=Boldyreva |first1=E. V. |last2=Naumov |first2=D. Y. |last3=Podberezskaya |first3=N. V. |last4=Virovets |first4=A. V. |title=Structure of lead(II) oxalate dihydrate |journal=Acta Crystallographica Section C: Crystal Structure Communications |date=15 November 1993 |volume=49 |issue=11 |pages=1882–1884 |doi=10.1107/S0108270193004652}}
The trihydrate has triclinic crystals with space group P{{overbar|1}} and unit cell dimensions and angles: a = 6.008 Å, b=6.671 Å, c=8.493 Å, α=74.70°, β=74.33°, and γ=80.98°. The unit cell volume is 314.41 Å3 with two formula per unit cell. Density is 3.69 g/cm3.{{cite journal |last1=Sheng-Hua |first1=Huang |last2=Ru-Ji |first2=Wang |last3=Mak |first3=Thomas C. W. |title=Crystal structures of isomorphous cadmium(II) and lead(II) oxalate trihydrates |journal=Journal of Crystallographic and Spectroscopic Research |date=April 1990 |volume=20 |issue=2 |pages=99–104 |doi=10.1007/BF01160959}}
Solubility
Lead(II) oxalate is insoluble in water. Its solubility is increased in presence of excess oxalate anions, due to the formation of the Pb(C2O4)22− complex ion.{{cite journal | author = Kolthoff, I.M. | title = The Solubility of lead Sulfate and of Lead Oxalate in Various Media | doi = 10.1021/j150419a004 | year = 1942 | last2 = Perlich | first2 = R. W. | last3 = Weiblen | first3 = D. | journal = Journal of Physical Chemistry | volume = 46 | issue = 5 | pages = 561}}