Wikipedia:WikiProject Chemicals/Chembox validation/VerifiedDataSandbox and Zinc chloride: Difference between pages

{{For|the battery type|Zinc–chloride battery}}

| Watchedfields = changed

| verifiedrevid = 477004315

| ImageFile = Zinc chloride anhydrous.jpg

| ImageCaption = Anhydrous

| ImageFile1 = Zinc chloride.jpg

| ImageName1 = Zinc chloride hydrate

| ImageCaption1 = Monohydrate

| ImageFile2 = Kristallstruktur Zinkchlorid.png

| OtherNames = {{ubl|Butter of zinc|Neutral zinc chloride (1:2)|Zinc bichloride (archaic)|Zinc(II) chloride}}

|Section1={{Chembox Identifiers

| CASNo = 7646-85-7

| CASNo_Ref = {{cascite|correct|CAS}}

| CASNo_Comment = Anhydrous

| CASNo1_Ref = {{cascite|changed|??}}

| CASNo1 = 29426-92-4

| CASNo1_Comment = Tetrahydrate

| CASNo2_Ref = {{cascite|changed|??}}

| CASNo2 = 21351-91-7

| CASNo2_Comment = Mixed hydrate

| ChEMBL_Ref = {{ebicite|correct|EBI}}

| ChEMBL = 1200679

| DrugBank = DB14533

| PubChem = 3007855

| RTECS = ZH1400000

| EINECS = 231-592-0

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

| UNII = 86Q357L16B

| UNNumber = 2331

| InChI = 1/2ClH.Zn/h2*1H;/q;;+2/p-2

| InChIKey = JIAARYAFYJHUJI-NUQVWONBAB

|Section2={{Chembox Properties

| Formula = {{chem2|ZnCl2}}

| Appearance = White [[hygroscopic]] and very [[Hygroscopy#Deliquescence|deliquescent]] crystalline solid

| Solubility = 432.0 g/100 g (25 °C)<br>615 g/100 g (100 °C)

| MeltingPtC = 290

| MeltingPt_ref = <ref name=Merck>{{cite book | author = O'Neil, M. J. | title = The Merck index : an encyclopedia of chemicals, drugs, and biologicals | publisher = Whitehouse Station | location = N. J. | year = 2001 | isbn = 978-0-911910-13-1 | display-authors = etal | url-access = registration | url = https://archive.org/details/merckindexency00onei }}</ref>

| BoilingPtC = 732

| BoilingPt_ref = <ref name=Merck />

| Solvent1 = ethanol

| Solubility1 = 430.0 g/100 ml

| MagSus = −65.0·10⁻⁶ cm³/mol

|Section3={{Chembox Structure

|Section6={{Chembox Pharmacology

| ATCCode_prefix = B05

| ATCCode_suffix = XA12

}}

|Section7={{Chembox Hazards

| MainHazards= Oral toxicity, irritant<ref>{{Cite web|url=https://www.sigmaaldrich.com/US/en/sds/sigald/208086?userType=undefined |title=Zinc chloride safety data sheet |publisher=[[Sigma-Aldrich]] |access-date=May 21, 2024 |date=March 2, 2024}}</ref>

| ExternalSDS = [https://www.sigmaaldrich.com/US/en/sds/sigald/208086?userType=undefined External SDS]

| GHSPictograms = {{GHS05}}{{GHS07}}{{GHS09}}

| GHSSignalWord = Danger

| HPhrases = {{H-phrases|302|314|410}}

| PPhrases = {{P-phrases|273|280|301+330+331|305+351+338|308+310}}

| NFPA-R = 0

| LD50 = {{ubl|350 mg/kg (rat, oral)|350 mg/kg (mouse, oral)|200 mg/kg (guinea pig, oral)|1100 mg/kg (rat, oral)|1250 mg/kg (mouse, oral)}}<ref name=IDLH/>

| IDLH = 50 mg/m³ (fume)<ref name=PGCH>{{PGCH|0674}}</ref>

| LC50 = 1260 mg/m³ (rat, 30 min)<br />1180 mg-min/m³<ref name=IDLH>{{IDLH|7646857|Zinc chloride fume}}</ref>

| REL = TWA 1 mg/m³ ST 2 mg/m³ (fume)<ref name=PGCH/>

| PEL = TWA 1 mg/m³ (fume)<ref name=PGCH/>

|Section8={{Chembox Related

| OtherAnions = {{ubl|[[Zinc fluoride]]|[[Zinc bromide]]|[[Zinc iodide]]}}

| OtherCations = {{ubl|[[Cadmium chloride]]|[[Mercury(II) chloride]]}}

'''Zinc chloride''' is an [[Inorganic chemistry|inorganic]] [[chemical compound]] with the [[chemical formula|formula]] ZnCl₂·''n''H₂O, with ''n'' ranging from 0 to 4.5, forming [[water of hydration|hydrates]]. Zinc chloride, anhydrous and its hydrates are colorless or white [[crystalline]] solids, and are highly [[Solubility|soluble]] in [[water]]. Five hydrates of zinc chloride are known, as well as four forms of anhydrous zinc chloride.<ref name="a"/> All forms of zinc chloride are [[deliquescent]]. Zinc chloride finds wide application in [[textile]] processing, [[flux (metallurgy)|metallurgical fluxes]], and chemical synthesis.

==Structure and properties==

Four crystalline forms ([[polymorphism (materials science)|polymorph]]s) of {{chem2|ZnCl2}} are known: α, β, γ, and δ. Each case features tetrahedral {{chem2|Zn(2+)}} centers.<ref name=Wells>{{cite book | author = Wells, A. F. | year = 1984 | title = Structural Inorganic Chemistry | location = Oxford | publisher = Clarendon Press | isbn = 978-0-19-855370-0 }}</ref>

{|class="wikitable" style="text-align:center"

|-

! Form !! [[Crystal system]] !! [[Pearson symbol]] !! [[Space group]] !! [[Crystal system#Four-dimensional space|No.]] !! [[Unit cell|''a'']] (nm) !!　''b'' (nm) !! ''c'' (nm) !! ''Z'' !! [[Density]] (g/cm³)

|-

| α || [[tetragonal]] || tI12 || I{{overline|4}}2d || 122 || 0.5398 || 0.5398 || 0.64223 || 4 || 3.00

|-

| β || tetragonal || tP6 || P4₂/nmc || 137 || 0.3696 || 0.3696 || 1.071 || 2 || 3.09

|-

| γ || [[monoclinic]] || mP36 || P2₁/c || 14 || 0.654 || 1.131 || 1.23328 || 12 || 2.98

|-

| δ || [[orthorhombic]] || oP12 || Pna2₁ || 33 || 0.6125 || 0.6443 || 0.7693 || 4 || 2.98

|}

Here ''a'', ''b'', and ''c'' are lattice constants, ''Z'' is the number of structure units per unit cell, and ρ is the density calculated from the structure parameters.<ref>{{cite journal | last1 = Oswald | first1 = H. R. | last2 = Jaggi | first2 = H. | title = Zur Struktur der wasserfreien Zinkhalogenide I. Die wasserfreien Zinkchloride | journal = Helvetica Chimica Acta | year = 1960 | volume = 43 | issue = 1 | pages = 72–77 | doi = 10.1002/hlca.19600430109 }}</ref><ref>{{cite journal | last1 = Brynestad | first1 = J. | last2 = Yakel | first2 = H. L. | title = Preparation and Structure of Anhydrous Zinc Chloride | journal = Inorganic Chemistry | year = 1978 | volume = 17 | issue = 5 | pages = 1376–1377 | doi = 10.1021/ic50183a059 }}</ref><ref>{{cite journal | last1 = Brehler | first1 = B. | title = Kristallstrukturuntersuchungen an ZnCl₂ | journal = Zeitschrift für Kristallographie | year = 1961 | volume = 115 | issue = 5–6 | pages = 373–402 | doi = 10.1524/zkri.1961.115.5-6.373 | bibcode = 1961ZK....115..373B }}</ref>

The orthorhombic form (δ) rapidly changes to one of the other forms on exposure to the atmosphere. A possible explanation is that the {{chem2|OH−}} ions originating from the absorbed water facilitate the rearrangement.<ref name=Wells/> Rapid cooling of molten {{chem2|ZnCl2}} gives a [[glass]].<ref>{{cite journal |author1=Mackenzie, J. D. |author2=Murphy, W. K. | title = Structure of Glass-Forming Halides. II. Liquid Zinc Chloride | journal = The Journal of Chemical Physics | year = 1960 | volume = 33 | issue = 2 | pages = 366–369 | doi = 10.1063/1.1731151 |bibcode=1960JChPh..33..366M }}</ref>

Molten {{chem2|ZnCl2}} has a high viscosity at its melting point and a comparatively low electrical conductivity, which increases markedly with temperature.<ref name = "prince">{{cite book | author = Prince, R. H. | year = 1994 | title = Encyclopedia of Inorganic Chemistry | editor = King, R. B. | publisher = John Wiley & Sons | isbn = 978-0-471-93620-6 }}</ref><ref>{{cite book | author = Ray, H. S. | year = 2006| title = Introduction to Melts: Molten Salts, Slags and Glasses | publisher = Allied Publishers | isbn = 978-81-7764-875-1 }}</ref> As indicated by a [[Raman scattering]] study, the viscosity is explained by the presence of polymers,<ref>{{cite book | author = Danek, V. | year = 2006 | title = Physico-Chemical Analysis of Molten Electrolytes | publisher = Elsevier | isbn = 978-0-444-52116-3 }}</ref>. [[Neutron scattering]] study indicated the presence of tetrahedral {{chem2|ZnCl4}} centers, which requires aggregation of {{chem2|ZnCl2}} monomers as well.<ref>{{cite journal | last1 = Price | first1 = D. L. | last2 = Saboungi | first2 = M.-L. | last3 = Susman | first3 = S. | last4 = Volin | first4 = K. J. | last5 = Wright | first5 = A. C. | title = Neutron Scattering Function of Vitreous and Molten Zinc Chloride | journal = Journal of Physics: Condensed Matter | year = 1991 | volume = 3 | issue = 49 | pages = 9835–9842 | doi = 10.1088/0953-8984/3/49/001 | bibcode = 1991JPCM....3.9835P | s2cid = 250902741 }}</ref>

===Hydrates===

Various hydrates of zinc chloride are known: {{chem2|ZnCl2(H2O)_{''n''}|}} with ''n'' = 1, 1.33, 2.5, 3, and 4.5.<ref name=Holleman>{{cite book |author1=Holleman, A. F. |author2=Wiberg, E. | title = Inorganic Chemistry | publisher = Academic Press | location = San Diego | year = 2001 | isbn = 978-0-12-352651-9 }}</ref> However, only the 1.33-hydrate, hemipentahydrate, trihydrate, and the heminonahydrate has been structurally elucidated.

The 1.33-hydrate, previously thought to be the hemitrihydrate, consists of ''trans''-Zn(H₂O)₄Cl₂ centers with the chlorine atoms connected to repeating ZnCl₄ chains. The hemipentahydrate, structurally formulated [Zn(H₂O)₅][ZnCl₄], consists of Zn(H₂O)₅Cl octahedrons where the chlorine atom is part of a [ZnCl₄]^2- tetrahedera. The trihydrate consists of distinct hexaaquozinc(II) cations and [[tetrachlorozincate]] anions; formulated [Zn(H₂O)₆][ZnCl₄]. Finally, the heminonahydrate, structurally formulated [Zn(H₂O)₆][ZnCl₄]·3H₂O also consists of distinct hexaaquozinc(II) cations and tetrachlorozincate anions like the trihydrate but has three extra water molecules.<ref name="1.33">{{cite journal |author1=H. Follner |author2=B. Brehler |title=Die Kristallstruktur des ZnCl2.4/3H2O |journal=Acta Crystallographica B |date=1970 |volume=26 |issue=11 |pages=1679–1682 |doi=10.1107/S0567740870004715 |bibcode=1970AcCrB..26.1679F |trans-title=The crystal structure of ZnCl2.4/3H2O |language=de}}</ref><ref name="hydrcrys">{{cite journal |author1=E. Hennings |author2=H. Schmidt |author3=W. Voigt |title=Crystal structures of ZnCl2·2.5H2O, ZnCl2·3H2O and ZnCl2·4.5H2O |journal=Acta Crystallographica E |date=2014 |volume=70 |issue=12 |pages=515–518 |doi=10.1107/S1600536814024738 |pmid=25552980 |language=en|pmc=4257420 }}</ref>

==Preparation and purification==

Anhydrous {{chem2|ZnCl2}} can be prepared from zinc and [[hydrogen chloride]] gas at 700 °C:<ref name="a" />

: {{chem2|Zn + 2 HCl → ZnCl2 + H2}}

Aqueous solutions may be readily prepared similarly by treating Zn metal, zinc carbonate, zinc oxide, and [[zinc sulfide]] with hydrochloric acid:<ref>{{cite book |doi=10.1002/0471238961.2609140307151504.a02.pub3 |chapter=Zinc Compounds |title=Kirk-Othmer Encyclopedia of Chemical Technology |date=2017 |first1=Frank E. |last1=Goodwin |pages=9–10 |isbn=978-0-471-23896-6 }}</ref>

: {{chem2|ZnS + 2 HCl + 4 H2O → ZnCl2(H2O)4 + H2S}}

Hydrates can be produced by evaporation of an aqueous solution of zinc chloride. Different evaporation temperatures produce different hydrates; for example, evaporation at room temperature produces the 1.33-hydrate.<ref name="1.33" /><ref name="old">{{cite journal |author1=F. Mylius |author2=R. Dietz |title=Über das Chlorzink. (Studien über die Löslichkeit der Salze XIV.) |journal=Zeitschrift für anorganische Chemie |date=1905 |volume=44 |issue=1 |pages=209–220 |doi=10.1002/zaac.19050440115 |language=en}}</ref> Lower evaporation temperatures produce higher hydrates.<ref name="hydrcrys" />

Commercial samples of zinc chloride typically contain water and products from hydrolysis as impurities. Such samples may be purified by [[recrystallization (chemistry)|recrystallization]] from hot [[dioxane]]. Anhydrous samples can be purified by [[sublimation (chemistry)|sublimation]] in a stream of [[hydrogen chloride]] gas, followed by heating the sublimate to 400&nbsp;°C in a stream of dry [[nitrogen]] gas.<ref name="eros">{{cite journal |doi=10.1002/047084289X.rz007.pub3|title=Zinc chloride|author=Glenn J. McGarvey Jean-François Poisson Sylvain Taillemaud|year=2016|journal=Encyclopedia of Reagents for Organic Synthesis|pages=1–20|isbn=978-0-470-84289-8}}</ref> Finally, the simplest method relies on treating the zinc chloride with [[thionyl chloride]].<ref>{{cite book | author = Pray, A. P. | title=Anhydrous Metal Chlorides|series = Inorganic Syntheses | year = 1990 | volume = 28 | pages = 321–322}}</ref>

==Reactions==

===The {{chem2|Zn2(2+)}} ion===

Molten anhydrous {{chem2|ZnCl2}} at 500–700&nbsp;°C dissolves zinc metal, and, on rapid cooling of the melt, a yellow diamagnetic glass is formed, which Raman studies indicate contains the {{chem2|Zn2(2+)}} ion.<ref name="Holleman"/>

===Chloride complexes===

A number of salts containing the [[tetrachlorozincate]] anion, {{chem2|[ZnCl4](2−)}}, are known.<ref name = "prince"/> "Caulton's reagent", {{chem2|[[Vanadium|V]]2Cl3([[thf]])6] [Zn2Cl6]}}, which is used in organic chemistry, is an example of a salt containing {{chem2|[Zn2Cl6](2−)}}.<ref>{{cite book | volume = 3 |editor1=Mulzer, J. |editor2=Waldmann, H. | title = Organic Synthesis Highlights | year = 1998 | publisher = Wiley-VCH | isbn = 978-3-527-29500-5 }}</ref><ref>{{cite journal | last1 = Bouma | first1 = R. J. | last2 = Teuben | first2 =J. H. | last3 = Beukema | first3 = W. R. | last4 = Bansemer | first4 = R. L. | last5 = Huffman | first5 = J. C. | last6 = Caulton | first6 = K. G. | title = Identification of the Zinc Reduction Product of VCl₃ · 3THF as <nowiki>[</nowiki>V₂Cl₃(THF)₆<nowiki>]</nowiki>₂<nowiki>[</nowiki>Zn₂Cl₆<nowiki>]</nowiki> | journal = Inorganic Chemistry | year = 1984 | volume = 23 | issue = 17 | pages = 2715–2718 | doi = 10.1021/ic00185a033 }}</ref> The compound {{chem2|[[caesium|Cs]]3ZnCl5}} contains [[Tetrahedral molecular geometry|tetrahedral]] {{chem2|[ZnCl4](2−)}} and [[Chloride|{{chem2|Cl−}}]] anions,<ref name=Wells/> so, the compound is not caesium pentachlorozincate, but caesium tetrachlorozincate chloride. No compounds containing the {{chem2|[ZnCl6](4−)}} ion (hexachlorozincate ion) have been characterized.<ref name=Wells/>

The compound {{chem2|ZnCl2*0.5HCl*H2O}} may be prepared by careful precipitation from a solution of {{chem2|ZnCl2}} acidified with HCl. It contains a polymeric anion {{chem2|(Zn2Cl5−)_{''n''}|}} with balancing monohydrated [[hydronium]] ions, {{chem2|H5O2+}} ions.<ref name=Wells/><ref>{{cite book | author-link = Joseph William Mellor | author = Mellow, J. W. | year = 1946 | title = A Comprehensive Treatise on Inorganic and Theoretical Chemistry | publisher = Longmans, Green }}</ref>

The [[coordination complex]] {{chem2|ZnCl2(NH2OH)2}} (zinc dichloride di(hydroxylamine)), known as Crismer's salt, releases [[hydroxylamine]] upon heating.<ref>{{cite book |doi=10.1002/9780470132401.ch2|chapter=Dichlorobis(hydroxylamine)zinc(II) (Crismer's Salt)|year=1967|volume=9|last1=Walker|first1=John E.|last2=Howell|first2=David M.|title=Inorganic Syntheses|pages=2–3|isbn=978-0-470-13240-1}}</ref>

===Aqueous solutions of zinc chloride===

Zinc chloride dissolves readily in water to give {{chem2|ZnCl_{''x''}(H2O)_{4−''x''}|}} species and some free chloride.<ref>{{cite journal | last1 = Irish | first1 = D. E. | last2 = McCarroll | first2 = B. | last3 = Young | first3 = T. F. | title = Raman Study of Zinc Chloride Solutions | journal = The Journal of Chemical Physics | year = 1963 | volume = 39 | issue = 12 | pages = 3436–3444 | doi = 10.1063/1.1734212 | bibcode = 1963JChPh..39.3436I }}</ref><ref>{{cite journal | last1 = Yamaguchi | first1 = T. | last2 = Hayashi | first2 = S. | last3 = Ohtaki | first3 = H. | title = X-Ray Diffraction and Raman Studies of Zinc(II) Chloride Hydrate Melts, ZnCl₂ · ''R'' H₂O (''R'' = 1.8, 2.5, 3.0, 4.0, and 6.2) | journal = The Journal of Physical Chemistry | year = 1989 | volume = 93 | issue = 6 | pages = 2620–2625 | doi = 10.1021/j100343a074 }}</ref><ref>{{cite journal |author1=Pye, C. C. |author2=Corbeil, C. R. |author3=Rudolph, W. W. | title = An ''ab initio'' Investigation of Zinc Chloro Complexes | journal = Physical Chemistry Chemical Physics | year = 2006 | volume = 8 | issue = 46 | pages = 5428–5436 | doi = 10.1039/b610084h | issn = 1463-9076 | pmid = 17119651 |bibcode=2006PCCP....8.5428P |s2cid=37521287 }}</ref> Aqueous solutions of {{chem2|ZnCl2}} are acidic: a 6&nbsp;[[concentration#Molarity|M]] aqueous solution has a [[pH]] of 1.<ref name=Holleman/> The acidity of aqueous {{chem2|ZnCl2}} solutions relative to solutions of other Zn²⁺ salts (say the sulfate) is due to the formation of the tetrahedral chloro aqua complexes where the reduction in coordination number from 6 to 4 further reduces the strength of the O–H bonds in the solvated water molecules.<ref>{{cite book |author = Brown, I. D. | year = 2006 | title = The Chemical Bond in Inorganic Chemistry: The Bond Valence Model | publisher = Oxford University Press | isbn = 978-0-19-929881-5 }}</ref>

In alkali solution, zinc chloride converts to various zinc hydroxychlorides. These include {{chem2|[Zn(OH)3Cl](2−)}}, {{chem2|[Zn(OH)2Cl2](2−)}}, {{chem2|[Zn(OH)Cl3](2−)}}, and the insoluble {{chem2|Zn5(OH)8Cl2*H2O}}. The latter is the mineral [[simonkolleite]].<ref>{{cite book | author = Zhang, X. G. | year = 1996 | title = Corrosion and Electrochemistry of Zinc | publisher = Springer | isbn = 978-0-306-45334-2 }} {{cite web |url=http://webmineral.com/data/Simonkolleite.shtml#.VEA-9SLF-vM |title= Simonkolleite Mineral Data |author=Staff writer(s)|website= webmineral.com |access-date= October 16, 2014}}</ref> When zinc chloride hydrates are heated, HCl gas evolves and hydroxychlorides result.<ref>{{cite journal |author1=Feigl, F. |author2=Caldas, A. | title = Some Applications of Fusion Reactions with Zinc Chloride in Inorganic Spot Test Analysis | journal = Microchimica Acta | year = 1956 | volume = 44 | issue = 7–8 | pages = 1310–1316 | doi = 10.1007/BF01257465 |s2cid=96823985 }}</ref>

When solutions of zinc chloride are treated with [[ammonia]], various [[transition metal ammine complex|ammine]] complexes are produced. These include {{chem2|Zn(NH3)4Cl2*H2O}} and on concentration {{chem2|ZnCl2(NH3)2}}.<ref>{{cite book | author = Vulte, H. T. | title = Laboratory Manual of Inorganic Preparations | publisher = Read Books | year = 2007 | isbn = 978-1-4086-0840-1 }}</ref> The former contains the {{chem2|[Zn(NH3)6](2+)}} ion,<ref name=Wells/> and the latter is molecular with a distorted tetrahedral geometry.<ref>{{cite journal | last1 = Yamaguchi | first1 = T. | last2 = Lindqvist | first2 = O. | title = The Crystal Structure of Diamminedichlorozinc(II), ZnCl₂(NH₃)₂. A New Refinement | journal = Acta Chemica Scandinavica A | year = 1981 | volume = 35 | issue = 9 | pages = 727–728 | doi = 10.3891/acta.chem.scand.35a-0727 | url = http://actachemscand.org/pdf/acta_vol_35a_p0727-0728.pdf | doi-access = free }}</ref> The species in aqueous solution have been investigated and show that {{chem2|[Zn(NH3)4](2+)}} is the main species present with {{chem2|[Zn(NH3)3Cl]+}} also present at lower {{chem2|NH3}}:Zn ratio.<ref>{{cite journal | last1 = Yamaguchi | first1 = T. | last2 = Ohtaki | first2 = H. | title = X-Ray Diffraction Studies on the Structures of Tetraammine- and Triamminemonochlorozinc(II) Ions in Aqueous Solution | journal = Bulletin of the Chemical Society of Japan | year = 1978 | volume = 51 | issue = 11 | pages = 3227–3231 | doi = 10.1246/bcsj.51.3227 | doi-access = free }}</ref>

===Zinc oxychloride cement===

Aqueous zinc chloride reacts with [[zinc oxide]] to form an [[amorphous]] [[cement]] that was first investigated in 1855 by [[Stanislas Sorel]]. Sorel later went on to investigate the related [[Sorel cement|magnesium oxychloride cement]], which bears his name.<ref>{{cite book |author1=Wilson, A. D. |author2=Nicholson, J. W. | year = 1993 | title = Acid-Base Cements: Their Biomedical and Industrial Applications | publisher = Cambridge University Press | isbn = 978-0-521-37222-0 }}</ref>

===Decomposition===

Anhydrous zinc chloride is able to melt and boil without any decomposition until 900 °C in an inert atmosphere. However, in the presence of oxygen, zinc chloride oxidizes to [[zinc oxide]] above 400 °C.<ref name="decomp">{{cite journal |author1=Frida Jones |author2=Honghi Tran |author3=Daniel Lindberg |author4=Liming Zhao |author5=Mikko Hupa |title=Thermal Stability of Zinc Compounds |journal=Energy & Fuels |date=2013 |volume=27 |issue=10 |pages=5663–5669 |doi=10.1021/ef400505u |language=en}}</ref>

When hydrated zinc chloride is heated, Zn(OH)Cl is produced instead of anhydrous zinc chloride:<ref>{{cite book | author = House, J. E. | year = 2008 | title = Inorganic Chemistry | publisher = Academic Press | isbn = 978-0-12-356786-4 }}</ref>

: {{chem2|ZnCl2*2H2O → Zn(OH)Cl + HCl + H2O}}

===Cellulose dissolution in aqueous solutions of {{chem2|ZnCl2}}===

[[Cellulose]] dissolves in aqueous solutions of {{chem2|ZnCl2}}, and zinc-cellulose complexes have been detected.<ref>{{cite journal |author1=Xu, Q. |author2=Chen, L.-F. | title = Ultraviolet Spectra and Structure of Zinc-Cellulose Complexes in Zinc Chloride Solution | journal = Journal of Applied Polymer Science | year = 1999 | volume = 71 | issue = 9 | pages = 1441–1446 | doi = 10.1002/(SICI)1097-4628(19990228)71:9<1441::AID-APP8>3.0.CO;2-G }}</ref> Cellulose also dissolves in molten {{chem2|ZnCl2}} hydrate and carboxylation and acetylation performed on the cellulose polymer.<ref>{{cite journal | last1 = Fischer | first1 = S. | last2 = Leipner | first2 = H. | last3 = Thümmler | first3 = K. | last4 = Brendler | first4 = E. | last5 = Peters | first5 = J. | title = Inorganic Molten Salts as Solvents for Cellulose | journal = Cellulose | year = 2003 | volume = 10 | issue = 3 | pages = 227–236 | doi = 10.1023/A:1025128028462 | s2cid = 92194004 }}</ref>

===Using zinc chloride for preparing other zinc salts===

Thus, although many zinc salts have different formulas and different [[crystal structure]]s, these salts behave very similarly in aqueous solution. For example, solutions prepared from any of the polymorphs of {{chem2|ZnCl2}}, as well as other halides (bromide, iodide), and the sulfate can often be used interchangeably for the preparation of other zinc compounds. Illustrative is the preparation of zinc carbonate:<ref name="a" />

:{{chem2|ZnCl2([[aqueous|aq]]) + [[sodium carbonate|Na2CO3]](aq) → [[zinc carbonate|ZnCO3]](s) + 2 [[sodium chloride|NaCl]](aq)}}

==Uses==

===In organic chemistry===

Zinc chloride is used as a catalyst or reagent in diverse reactions conducted on an industrial scale. The partial hydrolysis of [[benzal chloride]] in the presence of zinc chloride is the main route to [[benzoyl chloride]]. It serves as a catalyst for the production of methylene-bis(dithiocarbamate).<ref name="a">{{Ullmann | author1=Dieter M. M. Rohe | author2=Hans Uwe Wolf | title=Zinc Compounds | year=2007 | pages=1–6 | doi=10.1002/14356007.a28_537|}}</ref>

The combination of hydrochloric acid and {{chem2|ZnCl2}}, known as the "[[Lucas reagent]]", is effective for the preparation of alkyl chlorides from alcohols. Similar reactions are the basis of industrial routes from methanol and ethanol respectively to [[methyl chloride]] and [[ethyl chloride]].<ref>{{cite journal |author1=Kjonaas, R. A. |author2=Riedford, B. A. | title = A Study of the Lucas Test | journal = Journal of Chemical Education | year = 1991 | volume = 68 | issue = 8 | pages = 704 | doi = 10.1021/ed068p704 }}</ref>

====Laboratory syntheses====

Zinc chloride is a common reagent in the laboratory useful [[Lewis acid]] in organic chemistry.<ref>{{cite journal|title = Onium Ylide chemistry. 1. Bifunctional acid-base-catalyzed conversion of heterosubstituted methanes into ethylene and derived hydrocarbons. The onium ylide mechanism of the C₁ → C₂ conversion|first1 = George A.|last1 = Olah|first2 = Hans|last2 = Doggweiler|first3 = Jeff D.|last3 = Felberg|first4 = Stephan|last4 = Frohlich|first5 = Mary Jo|last5 = Grdina|first6 = Richard|last6 = Karpeles|first7 = Takashi|last7 = Keumi|first8 = Shin-ichi|last8 = Inaba|first9 = Wai M.|last9 = Ip|first10 = Koop|last10 = Lammertsma|first11 = George|last11 = Salem|first12 = Derrick|last12 = Tabor|journal = [[J. Am. Chem. Soc.]]|year = 1984|volume = 106|issue = 7|pages = 2143–2149|doi = 10.1021/ja00319a039}}</ref>

Molten zinc chloride catalyses the conversion of methanol to [[hexamethylbenzene]]:<ref name = HMB>{{cite journal|title = Hydrocarbons from Methanol|first = Clarence D.|last = Chang|pages = 1–118|doi = 10.1080/01614948308078874|journal = [[Catal. Rev. - Sci. Eng.]]|volume = 25|issue = 1|year = 1983}}</ref>

:{{chem2|15 CH3OH → C6(CH3)6 + 3 CH4 + 15 H2O}}

Other examples include [[catalysis|catalyzing]] (A) the [[Fischer indole synthesis]],<ref>{{OrgSynth | last1 = Shriner | first1 = R. L. | last2 = Ashley | first2 = W. C. | last3 = Welch | first3 = E. | title = 2-Phenylindole | year = 1942 | volume = 22 | pages = 98 | collvol = 3 |collvolpages = 725 | doi = 10.15227/orgsyn.022.00981955 | prep = cv3p0725 }}</ref> and also (B) [[Friedel-Crafts acylation]] reactions involving activated [[aromatic rings]]<ref>{{OrgSynth | last = Cooper | first = S. R. | title = Resacetophenone | collvol = 3 | collvolpages = 761 | prep = cv3p0761 | year = 1941 | volume = 21 | pages = 103 | doi = 10.15227/orgsyn.021.0103 }}</ref><ref>{{cite journal | last1 = Dike | first1 = S. Y. | last2 = Merchant | first2 = J. R. | last3 = Sapre | first3 = N. Y. | title = A New and Efficient General Method for the Synthesis of 2-Spirobenzopyrans: First Synthesis of Cyclic Analogues of Precocene I and Related Compounds | journal = [[Tetrahedron (journal)|Tetrahedron]] | year = 1991 | volume = 47 | issue = 26 | pages = 4775–4786 | doi = 10.1016/S0040-4020(01)86481-4 }}</ref>

[[File:ZnCl2 aromatics.gif |center|700px]]

Related to the latter is the classical preparation of the dye [[fluorescein]] from [[phthalic anhydride]] and [[resorcinol]], which involves a [[Friedel-Crafts acylation]].<ref>{{cite book | author = Furnell, B. S. | title = Vogel's Textbook of Practical Organic Chemistry | edition = 5th | publisher = Longman/Wiley | location = New York | year = 1989 }}</ref> This transformation has in fact been accomplished using even the hydrated {{chem2|ZnCl2}} sample shown in the picture above.

[[File:Preparation_of_Fluorescein.svg|center|500px]]

Zinc chloride also activates [[benzylic]] and [[allylic]] halides towards substitution by weak [[nucleophile]]s such as [[alkene]]s:<ref>{{cite journal |author1=Bauml, E. |author2=Tschemschlok, K. |author3=Pock, R. |author4=Mayr, H. | title = Synthesis of γ-Lactones from Alkenes Employing p-Methoxybenzyl Chloride as ⁺CH₂-CO₂⁻ Equivalent | journal = Tetrahedron Letters | year = 1988 | volume = 29 | issue = 52 | pages = 6925–6926 | doi = 10.1016/S0040-4039(00)88476-2 | url = http://epub.ub.uni-muenchen.de/3799/1/086.pdf }}</ref>

[[File:ZnCl2 benzylation.gif|center|500px]]

In similar fashion, {{chem2|ZnCl2}} promotes selective [[sodium cyanoborohydride|{{chem2|Na[BH3(CN)]}}]] reduction of tertiary, allylic or benzylic halides to the corresponding hydrocarbons.<ref name="eros" />

Zinc chloride is also a useful starting reagent for the synthesis of many [[organozinc]] reagents, such as those used in the palladium catalyzed [[Negishi coupling]] with [[aryl halide]]s or [[vinyl halide]]s.<ref>{{cite journal |author1=Kim, S. |author2=Kim, Y. J. |author3=Ahn, K. H. | title = Selective Reduction of Tertiary, Allyl, and Benzyl Halides by Zinc-Modified Cyanoborohydride in Diethyl Ether | journal = Tetrahedron Letters | year = 1983 | volume = 24 | issue = 32 | pages = 3369–3372 | doi = 10.1016/S0040-4039(00)86272-3}}</ref> In such cases the organozinc compound is usually prepared by [[transmetallation]] from an [[organolithium]] or a [[Grignard reagent]], for example:

[[File:ZnCl2 Negishi.gif|center|500px]]

Zinc [[enolate]]s, prepared from alkali metal enolates and {{chem2|ZnCl2}}, provide control of [[stereochemistry]] in [[aldol condensation]] reactions due to [[chelation]] on to the zinc. In the example shown below, the ''[[threo]]'' product was favored over the ''[[erythro]]'' by a factor of 5:1 when {{chem2|ZnCl2}} in [[dimethoxyethane|DME]]/[[diethyl ether|ether]] was used.<ref>{{cite journal |author1=House, H. O. |author2=Crumrine, D. S. |author3=Teranishi, A. Y. |author4=Olmstead, H. D. | title = Chemistry of Carbanions. XXIII. Use of Metal Complexes to Control the Aldol Condensation | journal = Journal of the American Chemical Society | year = 1973 | volume = 95 | issue = 10 | pages = 3310–3324 | doi = 10.1021/ja00791a039 }}</ref> The chelate is more stable when the bulky phenyl group is pseudo-[[equatorial bond|equatorial]] rather than pseudo-[[axis of rotation|axial]], i.e., ''threo'' rather than ''erythro''.

[[File:ZnCl2 aldol.gif|center|600px]]

===As a metallurgical flux===

The use of zinc chloride as a flux, sometimes in a mixture with [[ammonium chloride]] (see also [[Zinc ammonium chloride]]), involves the production of HCl and its subsequent reaction with surface oxides.

Zinc chloride reacts with metal oxides (MO) to give derivatives of the idealized formula {{chem2|MZnOCl2}}.<ref name="HOWI">{{cite book|last=Wiberg|first=Nils|title=Lehrbuch der Anorganischen Chemie |trans-title=Holleman & Wiberg, Textbook of Inorganic chemistry |language=de|publisher=de Gruyter, Berlin|year=2007 |page = 1491|isbn=978-3-11-017770-1}}</ref>{{Additional citation needed|date=October 2017|reason=Suggested reaction is bit dubious and it is not mentioned in some major chemistry textbooks (or anywhere else that I could find).}} This reaction is relevant to the utility of {{chem2|ZnCl2}} solution as a [[flux (metallurgy)|flux]] for [[soldering]] — it dissolves [[Passivation (chemistry)|passivating]] oxides, exposing the clean metal surface.<ref name="HOWI"/> Fluxes with {{chem2|ZnCl2}} as an active ingredient are sometimes called "tinner's fluid".

Zinc chloride forms two salts with ammonium chloride: {{chem2|[NH4]2[ZnCl4]}} and {{chem2|[NH4]3[ZnCl4]Cl}}, which decompose on heating liberating HCl, just as zinc chloride hydrate does. The action of zinc chloride/ammonium chloride fluxes, for example, in the [[hot-dip galvanizing]] process produces {{chem2|H2}} gas and ammonia fumes.<ref>{{cite book | title = ASM handbook | year = 1990 | author = American Society for Metals | publisher = ASM International | isbn = 978-0-87170-021-6 }}</ref>

===In textile and paper processing===

Concentrated aqueous solutions of zinc chloride (more than 64% weight/weight zinc chloride in water) are capable of dissolving [[starch]], [[silk]], and [[cellulose]].{{Citation needed|date=May 2024}}

Relevant to its affinity for these materials, {{chem2|ZnCl2}} is used as a fireproofing agent and in fabric "refresheners" such as Febreze. [[Vulcanized fibre]] is made by soaking paper in concentrated zinc chloride.

===Other uses===

The [[smoke composition|zinc chloride smoke mixture]] ("HC") used in [[smoke grenades]] contains zinc oxide, [[hexachloroethane]] and granular [[aluminium]] powder, which, when ignited, react to form zinc chloride, carbon and [[aluminium oxide]] smoke, an effective [[smoke screen]].<ref>{{cite book | author = Sample, B. E. | year = 1997 | title = Methods for Field Studies of Effects of Military Smokes, Obscurants, and Riot-control Agents on Threatened and Endangered Species | publisher = DIANE Publishing | isbn = 978-1-4289-1233-5 }}</ref>

[[Ninhydrin]] reacts with [[amino acid]]s and [[amine]]s to form a colored compound "Ruhemann's purple" (RP). Spraying with a zinc chloride solution forms a 1:1 complex RP:{{chem2|ZnCl(H2O)2}}, which is more readily detected as it fluoresces more intensely than RP.<ref>{{cite book | author = Menzel, E. R. | year = 1999 | title = Fingerprint Detection with Lasers | publisher = CRC Press | isbn = 978-0-8247-1974-6 }}</ref>

Dilute aqueous zinc chloride was used as a disinfectant under the name "Burnett's Disinfecting Fluid".<ref>{{cite book | author = Watts, H. | year = 1869 | title = A Dictionary of Chemistry and the Allied Branches of Other Sciences | publisher = Longmans, Green | url = https://archive.org/details/adictionarychem11wattgoog }}</ref> From 1839 [[Sir William Burnett]] promoted its use as a disinfectant as well as a wood preservative.<ref>{{cite journal |last1=McLean |first1=David |title=Protecting wood and killing germs: 'Burnett's Liquid' and the origins of the preservative and disinfectant industries in early Victorian Britain |journal=Business History |date=April 2010 |volume=52 |issue=2 |pages=285–305|doi=10.1080/00076791003610691 |s2cid=154790730 }}</ref> The Royal Navy conducted trials into its use as a disinfectant in the late 1840s, including during the [[1846–1860 cholera pandemic|cholera epidemic of 1849]]; and at the same time experiments were conducted into its preservative properties as applicable to the shipbuilding and railway industries. Burnett had some commercial success with his eponymous fluid. Following his death however, its use was largely superseded by that of [[carbolic acid]] and other proprietary products.

==Natural occurrence==

Anhydrous zinc chloride or its hydrates is not known in nature. However, the related [[zinc chloride hydroxide monohydrate]] is known as simonkolleite in nature.<ref>{{cite web |title=Simonkolleite |url=https://mindat.org/min-3668.html |website=mindat.org |access-date=20 February 2024}}</ref>

==References==

{{Reflist|colwidth=30em}}

==Further reading==

* N. N. Greenwood, A. Earnshaw, ''Chemistry of the Elements'', 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997.

* {{RubberBible86th}}

* ''The Merck Index'', 7th edition, Merck & Co, Rahway, New Jersey, USA, 1960.

* D. Nicholls, ''Complexes and First-Row Transition Elements'', Macmillan Press, London, 1973.

* J. March, ''Advanced Organic Chemistry'', 4th ed., p.&nbsp;723, Wiley, New York, 1992.

* G. J. McGarvey, in ''Handbook of Reagents for Organic Synthesis, Volume 1: Reagents, Auxiliaries and Catalysts for C-C Bond Formation'', (R. M. Coates, S. E. Denmark, eds.), pp.&nbsp;220–3, Wiley, New York, 1999.

==External links==

* [http://muby.itgo.com/zincchloride.html Grades and Applications of Zinc Chloride]

* [https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=5727 PubChem ZnCl₂ summary].

{{Zinc compounds}}

{{Chlorides}}

{{Authority control}}

{{DEFAULTSORT:Zinc Chloride}}

[[Category:Chlorides|zinc]]

[[Category:Zinc compounds|chloride]]

[[Category:Inorganic compounds]]

[[Category:Metal halides]]

[[Category:Deliquescent materials]]