Calcium phosphide: Difference between revisions

| Watchedfields = changed

| verifiedrevid = 433337327

| ImageFile = 429048-ICSD.png<!--high T phase of Ca3P2 according to Cava et al. Greenish=Ca-->

| ImageSize = 180px

| IUPACName = Calcium phosphide

|Section1={{Chembox Identifiers

| CASNo_Ref = {{cascite|correct|??}}

| CASNo = 1305-99-3

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = IQZ9FY9THC

| PubChem = 4337964

| ChemSpiderID = 14097

| EINECS = 215-142-0

| StdInChI=1S/3Ca.2P/q;;+2;2*-1

| StdInChIKey = GOKCLHLCMXPYLQ-UHFFFAOYSA-N

| SMILES = [Ca+2].[Ca+2].[Ca+2].[P-3].[P-3]

|Section2={{Chembox Properties

| Formula = Ca₃P₂

| MolarMass = 182.18 g/mol

| Appearance = red-brown crystalline powder or grey lumps

| Density = 2.51 g/cm³

| MeltingPt = ~1600 °C

| BoilingPt =

| Solubility = decomposes

|Section7={{Chembox Hazards

| MainHazards = Source of toxic [[phosphine]], dangerous reaction with water

| NFPA-H = 4

| NFPA-F = 0

| NFPA-R = 3

| NFPA-S = W

| GHSPictograms = {{GHS02}}{{GHS05}}{{GHS06}}{{GHS09}}

| GHSSignalWord = Danger

| HPhrases = {{H-phrases|260|300|311|318|330|400}}

| PPhrases = {{P-phrases|231+232|233|280|301+310|405|501}}

| AutoignitionPt =

'''Calcium phosphide''' ('''CP''') is the [[inorganic compound]] with the formula Ca₃P₂. It is one of several [[phosphide]]s of calcium, being described as the salt-like material composed of Ca²⁺ and P³⁻. Other, more exotic calcium phosphides have the formula [[Calcium monophosphide|CaP&nbsp;/&nbsp;Ca₂P₂]], CaP₃, and Ca₅P₈.

Ca₃P₂ has the appearance of red-brown crystalline powder or grey lumps. Its trade name is '''Photophor''' for the incendiary use or '''Polytanol''' for the use as [[rodenticide]].{{cn|date=September 2023}}

==Preparation and structure==

It may be formed by reaction of the elements,<ref name=cava/> but it is more commonly prepared by [[Carbothermic reaction|carbothermal reduction]] of [[calcium phosphate]]:<ref>{{Greenwood&Earnshaw2nd}}</ref>

:Ca₃(PO₄)₂ + 8 C → Ca₃P₂ + 8 CO

The structure of the room temperature form of Ca₃P₂ has not been confirmed by X-ray crystallography. A high temperature phase has been characterized by [[Rietveld refinement]]. Ca²⁺ centers are octahedral.<ref name=cava>{{cite journal |last1=Xie |first1=Lilia S. |last2=Schoop |first2=Leslie M. |last3=Seibel |first3=Elizabeth M. |last4=Gibson |first4=Quinn D. |last5=Xie |first5=Weiwei |last6=Cava |first6=Robert J. |title=A new form of Ca3P2 with a ring of Dirac nodes |journal=APL Materials |volume=3 |pages=083602 |issue=8 |year=2015 |arxiv=1504.01731 |bibcode=2015APLM....3h3602X |s2cid=119272970 |doi=10.1063/1.4926545}}</ref>

==Uses==

Metal phosphides are used as a [[rodenticide]]. A mixture of food and calcium phosphide is left where the rodents can eat it. The acid in the digestive system of the rodent reacts with the phosphide to generate the toxic gas [[phosphine]]. This method of vermin control has possible use in places where rodents immune to many of the common [[warfarin]]-type ([[anticoagulant]]) poisons have appeared. Other pesticides similar to calcium phosphide are [[zinc phosphide]] and [[aluminium phosphide]].

Calcium phosphide is also used in [[fireworks]], [[torpedo]]es, self-igniting naval [[pyrotechnic flare]]s, and various water-activated ammunition. During the 1920s and 1930s, [[Charles Kingsford Smith]] used separate buoyant canisters of [[calcium carbide]] and calcium phosphide as naval flares lasting up to ten minutes. It is speculated that calcium phosphide—made by boiling bones in urine, within a closed vessel—was an ingredient of some ancient [[Greek fire]] formulas.<ref>[[Colin McEvedy]] (1992),''The New Penguin Atlas of Medieval History'', New York: Penguin.</ref>

Calcium phosphide is a common impurity in calcium carbide, which may cause the resulting phosphine-contaminated [[acetylene]] to ignite spontaneously.<ref>{{cite web |title=Calcium Phosphide |url=https://cameochemicals.noaa.gov/chemical/314 |website=CAMEO Chemicals |publisher=NOAA Office of Response and Restoration, US |access-date=2016-08-26}}</ref>

==See also==

* [[Phosphorus]]

{{reflist}}

{{Rodenticides}}

{{Phosphorus compounds}}