Recrystallisation Benzoic Acid Determination Melting P ...

of and

of of its

and

Recrystallisation Benzoic Acid Determination Melting Point

Recrystallisation Benzoic Acid D

Producing pure substances is a very important process, especially in the pharmaceutical industry. Separating insoluble solids from solvents is easily achieved using a simple technique called filtration. Soluble solids again are easily separated from solvents by evaporation, and

Fig.1 Filtration to remove insoluble impurities

Beaker containing benzoic acid dissolved in minimum amount of boiling water

Fig.1 Finding the melting point of benzoic acid

Thermometer

tapped sharply against the desk causing the crystals to fall to the sealed end. When about 3 mm of crystals are in the base of the tube it is placed in the oil bath. The

chromatography is used to separate a mixture of liquids. But

what happens when we have two soluble solids that we want

to separate? In this lesson we will look at recrystallisation, a

Filter funnel with fluted filter paper to

Benzoic acid crystals

commonly-used process in the pharmaceutical industry.

speed up the filtrarion process. Insoluble

impurities left behind as residue

Producing pure substances is a very important process,

Aluminium block

Wheastpiserceiacrllyystailnlisatthioen? pharmaceutical industry. Separating

Fig.1 Filtration to remove insoluble impurities

temperature at which the sample begins to melt and the temperature at which it is completely melted are recorded.

To double check your result, mix a sample of benzoic acid with some

insoluble solids from solvents is easily achieved using a Recrystallisation is a very important purification technique, purifying

substances by removing unwanted by-products. It is also used

Conical flask with hot concentrated benzoic acid solution which still contains

simple technique called filtration. to manufacture the correct crystal size and shape of a material.

These factors can have a very significant impact on how a

Soluble

solids

again soluble impurities

are easily separated from solvents medicine acts when taken by a patient. The same principles and

techniques of recrystallisation can be applied both on a laboratory and

by

evaporation,

and

pure benzoic acid. If both

Bunsen burner

are pure benzoic acid the

Beaker containing benzoimcealtincgidpdoinist swoilllvreedmaiinn

minimum

amount

of

boilintishgenswoatmapetuebrerut

if the sample benzoic acid

then the melting point will

inducstrhy srcoalem. atography is used to separate a mixture of liquids. But

be lowered.

Whwathaartehtahpepperinnsciwplhesenbewheinhdave two soluble sFiog.2lidAftser that we want cooling, the remaining solution is filtered off

rectroyssteapllaisraattieon??In this lesson we will look at recrystallPiusreabetnizooicnac,id acystals

commonly-used process in the pharmaceutical The process depends on two principles; the fact that substances tend

to be more soluble in a hot solvent than in cold solvent, and that each

industry.

solute tends to behave as though it were alone in the solvent.

B?chner funnel

How do I know I have a pure substance?

The melting Fpoilintet orf fausnubnsetalncweiitshnoftluthteeedxafcitltpeorintpaat wpheicrhtiot melts bunuttirlaitthhearstchoesmrpapnelgeeeteodlyf tmeumeplpteetdrha. Tetuhreefisgltfrrreoaamtreiwrothhneenrptahrneogsecatmehepslmesso.srIetnairmstspotuolrumitibeelslte present. A rainmgepouf lreistisethsanle1ft?Cbinedhicianteds aapsurreessuibdstuanece.

HoWw dhoaI tknioswrwehcatrsyoslvteantltloisuaset?ion?

How is crystallisation used in industry?

Using the correct solvent is a very important part of the process. The

soluRte emcusrtybse tinaslolliusbaletiinotnhe sioslveant avteroroym tiemmppeorartutrae,natndpaus rthifie cation technique, purifying tinecmrepsaeusraebtsu.srIettaiosfnatlhcseoesismolpvoebrnttaynintctrrheeaatmstehseo, ivmthipenusgroitileusbuiplnitryewsoeafnttnhaetreesodsloultuebblaeylsi-onproducts. It is also used

the stoolvenmt aat rnooumfatecmtpuerraeturethaned incsoolrurbelecatt higchreyr stetmaplerastuizrees. and shape of a material.

The use of crystallisation in the pharmaceutical industry is an important

process for controlling the physical properties, yield and purity of an

Active PharmCacoenutiiccaal lInfglaresdkienwt (itAhPI)h. oMtancyopnrcodeuncttiroan teprdocesses

use crystallibsaetionnzion itcheaficniadl sstaogeluotfiomnanwufahcitcurhe tsotailclhcieoventthaeisnes

targets. a better

Ruencdesenrost talaudnvbdailnnecgeoismfinthpceruypsrritoatcileleisssast.ioTnhepsroecaedsvsamncoensitoarlliongw

allow for crystals

An eTxhceellesnet sufbastcantocersfor cshaonwinghtahivs eprocaess viserbyenzosicigacnidificant impact on how a b(Cy6iHtms5CleoOwdOimHc)e.ilntAinegmopaloecicnuttlsaorf c1wr2y2shta?eCl n,rabthetenarzkothiecannacaindbioiysniucascerdypsatasalt,aisnehnaonwttn.i- The same principles and micrtoebicalhagneinqt uanedsisofofunred cinrtyoostthapallsitsesa, tmioounthcwaasnhebs, ecoasmpepticlised both on a laboratory and and idnedoduorsatnrtsy. scale.

Impure benzoic acid contains the impurities phthalic acid and

B?chner flask Water containing soluble impurities

with specific physical properties, for example particle size and shape, to be created. It is possible to produce crystals of varying particle size, shape and form polymorphs of the same substance, but only one will be suitable for drug development and manufacture.

In industry, the way an API is filtered and dried can have a very significant impact on the physical properties of the material.

benzylbenzoate. If the impure sample is dissolved in a minimal volume of hot solvent ? in this case boiling water ? and filtered to remove insoluble

How can we check the purity of

What are the principles behind impurities, the resulting solution will contain dissolved benzoic acid as

well as dissolved impurities.

our substance?

Fig.2 After cooling, tChealrceumlatinininggtshoelupteiornceisnfitaltgeereydieoflfd

A pure substance has a fixed melting point while an impure substance

After the crystallisation process the amount of sample will have been

recrystallisation? Upon cooling, the benzoic acid crystals comes out of solution as its

solubiluty in the solvent decreases. The impurities will remain in solution

melts over a wide range of temperatures and at a lower temperature than the pure substance. The melting points of almost all substances

Purerpeubdreuecnsezudboasictsainamccpeiudwriactiseyspsrhteaaslvesenbt einenthreeimniotivael dim. Tpoucrealscaumlapteleh, othwempeurccheontfatghee

and Tcahnebepfilrteorecdeosff.s depends on two principles; the factarethaavatilasbulebinstatablnesc. es tend

It is are

vwteoorrynbi,mebpeocmratauonsterweohregsnaonciaclurrsybuinblgestoauinntctehasiscehaxnpoebtreimsaeobnsltvotrhebanetdrtutbthhbroeaur ngghloivtnhees

cold

sTaoloumclhvineeicunkmtth,beloamcnkedlwtinhtgichhpaohtianstepaalacthcheerma ofemwetcerrysintaslesrtoefd.theUsseamaphleotopnlaatne

skin,saondluatsewetell,ngodgsgletsoshboeulhd abevweoranstotphrooteuctgyhouriteywesefrroemaholot ne intothheeatstohelvbelonckt.slowly. Watch the crystals carefully and note the

liquids which may spray out from the flask.

temperature at which they begin to melt and the temperature at which

yield is calculated.

Percentage yield = Mass of pure sample (after recrystallisation) x 100

Mass of imBp?urcehsanmeprlefu(bnenfoerelrecrystallisation)

The percentage yield is a good indicator of the purity of the initial

they have all melted. Compare this value with the value found on the

sample. A high percentage yield implies a low concentration of

bottle of pure substance. Another method of checking the melting point of

impurities, whereas a low percentage yield indicates a sample with a

How do I know what solvent to use? crystals is to use a narrow capillary tube in an oil bath. The capillary tube has one end open and the other end sealed. The open end is pressed

lot of impurities.

into fine crystals of the substance and the turned upside down and

Using the correct solvent is a very important part of the process. The

solute must be insoluble in the solvent at room temperature, and as the

temperature of the solvent increases, the solubility of the solute also

increases. It is also important that the impurities present are soluble in

the solvent at room temperature and insoluble at higher temperatures.

Glaxo comp the s a lea infect nervo The comm qualit to live World manu Curra the a facilit in de chem The C site w autom with P We a GSK' Type Canc Glaxo Dung Dubli

You Glax www

An excellent substance for showing this process is benzoic acid (C6H5COOH). A molecular crystal rather than an ionic crystal, shown by its low melting point of 122 ?C, benzoic acid is used as an antimicrobial agent and is found in toothpastes, mouthwashes, cosmetics and deodorants.

B?chner flask Water containing soluble impurities

Impure benzoic acid contains the impurities phthalic acid and benzylbenzoate. If the impure sample is dissolved in a minimal volume of hot solvent ? in this case boiling water ? and filtered to remove insoluble impurities, the resulting solution will contain dissolved benzoic acid as well as dissolved impurities.

Upon cooling, the benzoic acid crystals comes out of solution as its solubiluty in the solvent decreases. The impurities will remain in solution and can be filtered off.

How can we check the purity of our substance?

A pure substance has a fixed melting point while an impure substance melts over a wide range of temperatures and at a lower temperature than the pure substance. The melting points of almost all substances are available in tables.

It is very important when carrying out this experiment that rubber gloves are worn, because organic substances can be absorbed through the skin, and as well, goggles should be worn to protect your eyes from hot liquids which may spray out from the flask.

To check the melting point place a few crystals of the sample on an aluminium block which has a thermometer inserted. Use a hot plate to heat the block slowly. Watch the crystals carefully and note the temperature at which they begin to melt and the temperature at which they have all melted. Compare this value with the value found on the bottle of pure substance. Another method of checking the melting point of crystals is to use a narrow capillary tube in an oil bath. The capillary tube has one end open and the other end sealed. The open end is pressed into fine crystals of the substance and the turned upside down and

and of its

of and

of its

Recrystallisation Benzoic Acid Determination Melting Point

Determination Melting Point

Producing pure substances is a very important process, especially in the pharmaceutical industry. Separating

Fig.1 Filtration to remove insoluble impurities

insoluble solids from solvents is easily achieved using a simple technique called filtration. Soluble solids again are easily separated from solvents by evaporation, and

Beaker containing benzoic acid dissolved in minimum amount of boiling water

chromatography is used to separate a mixture of liquids. But

what happens when we have two soluble solids that we want

to separate? In this lesson we will look at recrystallisation, a

Filter funnel with fluted filter paper to

commonly-used process in the pharmaceutical industry.

speed up the filtrarion process. Insoluble

impurities left behind as residue

tapped sharply against the

WhFaigt.i1s Freincdriynsgttahlelismaetilotinng?

desk causing the crystals to

Recpryostianllitsaotiofnbies nazvoeiryc iamcpoidrtant purification technique, purifyinfgall to the sealed end. WheConnical flask with hot concentrated

substances by to manufacture

removing unwanted by-products. It

the correct Tchryestraml osimzeeatendr shape

is of

aalsmoatuesrieaadl.bout

3

mm

of

crystals

abreenzoic acid solution which still contains soluble impurities

These factors can have a very significant impact on how ina the base of the tube it is

placed medicine acts when taken by a patient. The same principles and

techniques of recrystallisation can be applied both on a laboratory and

in

the

oil

bath.

The

industry scale.

temperature at which the

Fig.1 Finding the melting point of benzoic acid

Thermometer

Benzoic acid crystals Aluminium block

Bunsen burner

tapped sharply against the desk causing the crystals to fall to the sealed end. When about 3 mm of crystals are in the base of the tube it is placed in the oil bath. The temperature at which the sample begins to melt and the temperature at which it is completely melted are recorded.

To double check your result, mix a sample of benzoic acid with some pure benzoic acid. If both are pure benzoic acid the melting point will remain the same but if the sample is not pure benzoic acid then the melting point will be lowered.

sample begins to melt and

What are the principles behind

the temFipg.2erAaftetrucroeolinga, tthe wremhaiicnihng solution is filtered off

How do I know I have a pure substance?

recrystaBlleisnazotiiconac?id crystals

it is completely mPeureltbeendzoicaacried cystals

The melting point of a substance is not the exact point at which it melts

The process depends on two principles; the fact that substances tenrdecorded.

to be more soluble in a hot solvent than in cold solvent, and that each

solute teAnldusmtoinbieuhmavebalos cthkough it were alone in the solvent.

To double

check

your

but rather the range of temperatures from when the samples starts to melt

B?chner funnGel laxoSmithKline isupnraetisleitnlhet.aaAs dcraoinmngpgeleotferlleeysmsseethltaaendrc.1Th?hCe-bignrdaeiacstaeetredtshae prpauhnrgeaesruthmbesmataocnrceeeiu.mtpiucraitiel s company committed to excellence and innovation. We are

How do I know what solvent to use?

result, mix a sample of

benzoic acid with some

Using the correct solvent is a very important part of the process. The

solute must be insoluble in the solvent at room temperature, and as thpe ure benzoic acid. If both

temperatuBreuonfstehen

increases. It is also

sboulvrennet rincreases,

important that the

are the solubility of the solute also

impurities present are soluble in

pure

benzoic

acid

the

the solvent at room temperature and insoluble at higher temperaturesm. elting point will remain

An excellent substance for showing this process is benzoic acitdhe same but if the sample

is (C6H5COOH). A molecular crystal rather than an ionic crystal, shown

by its low melting point of 122 ?C, benzoic acid is used as an anti-

not

pure

benzoic

acid

microbial agent and is found in toothpastes, mouthwashes, cosmetictshen the melting point will

and deodorants.

be lowered.

the second largest Hlifoewscisiecnrcyestcaollmispaatinoyninustehde iwnoirnldduasntdryh?ave

a leadership positiTohne usienoffcoryustrallimsataiojnoinr thtehpeharrampaceeuutticical inadurestraysis a?n imapnorttia-nt

infectives, gastroinptreoscetsins faolr/cmonetrotallinbgothliecp,hyrseicaslppirroapetrotiersy, yiealdnadnd cpuerintytroaf aln

nervous system.

Active Pharmaceutical Ingredient (API). Many production processes use crystallisation in the final stage of manufacture to achieve these

targets. Recent advances in crystallisation process monitoring allow for

The source of oura cbeottmer punedetirtsitvanedinag dofvthaenptraocgeess. iTshestehaedvaenncees raglloyw carynstdals B?chner flaskcommitment of ourwtoeitbhmescppreelcaoitfieycde.pheItysissi.cpaolsOpsriboulperetrotmiepsrio,sdfosuricoeexncarmyispstlaelstpooafrtviicamlreypisnigzreopaavnretdiclsethhsaiepzee,,

Water

containqinug saolluibtlye imopufrihtieus man

lifeshtaopeeanndafborlmeppoleymooprplhes otfothde soamme sourbest,anfecee, bl ubt oentltyeorneawnilldbe suitable for drug development and manufacture.

to live longer.

In industry, the way an API is filtered and dried can have a very significant

How do I know I have a pure substance? IbhiwUsaIasmmtoknroepeieTbupsiplpdntnloulsuuvznhw,urnbcaoeyrraeiaosietetllrltcnubvnryiisdeorndelteiybisamboe,nmnsia,etelitsbztninsptnn?oohehefihotwgztlalcheivtnlero.,aeteaeetteriatlrtuircAedsl.hshen,nssIoteidgfitseumchglatrwovholbcctoapeogeheifeainprfnudge.nngsmigtrrmlnezaoeidagtosncpiscbepeioiinoeuanccocsslnlrruhri.greeltasetitooyaniucasoetiouignibsafnendlgedmsfswollwstceoybaapa.friutntellTsyhtelemtcsheswcerstietesho?auomseindiltsraimsbmntcihlnseaptapcpdtssxiaeonnuooeupfitrnmdplredlabivrittrtrieeeiea.sioiene1mdrsstseTtsaeocieudowbnc?lhnveustCiptratleotoeylehtmdrorhiortebssehiuagifbmnnemartesfidrnlramedoinroueciyolznvotabuiehoaeclbitmsrtanviioiceotacnofseturrnisalohdotugwgorcemlamhluelioudsthsatevhhtibnohaeieeootladneeessstfxnarptachuntergepsHoAmtaTateohoorlsaueaeupoimhutlnmcutanrheshwrivbtneaethaepositcseuisvalcklaumtumetephbtbaratbeulhssbewaornnetselbaoisrwnchlnmtcsoetwicatekudicaeaecbkeil.nbewrtmshihlnthretscaaasglicsocpsnnei.htwhtgcpau?oeeolmheyfi.ri.anmoxiTcsteetWfhikdpteaeelaetlmatmlsstmctthcehhpeeeletlreittmanrihnageofgtpeumpwcrpoueeroiystncreisntriartytwtanssilynhdstoasilfleaecosrataWmCtfictanfaohlreamnhefducaeofol.tueidomrhisnrlwllremteUylpiauaedtaussvrycalibferal-ceenattmwesidaiaelnuscmvpouibhlmnlntpdeebsopuoeastytetaorpmtrena,ipannintlnlcnudtaoeahcegwwrtgneeeesynprhesetrisdoccoieichhtevemeeeniCArpysmPeswimufertpedtpasrlserdueacalri5licoescisencstsneo0tuhyttdnucoaberf0agnasygel3celtsacm,tarosihyp7uyinntmieaetlsvcaieealetpndpeetnaedouhbcel=wglrdariyipsio.raltsclaiiMiseiyMstluncta1eisahpaoahtsn1glrhs,linseecsepa0t.socpvmorradef,oeprfioi0noempplbatecuem0pseiaeirrnnuernets.0rnintcpseeyshasdrseeotme1ahoopimmnpuen9fqAlfipeeotttna7hiluvta(eamoewaed5l(afgdombitpm,esho.eulrealiTf.pnooretutoeweturyecymOrrcrorieeraayifecaselluscs.ctCahraaaunlrymmlmdllseioardstpCptaeamaerlltleliekiohnus,enihaotwsruht)winairoetlSflnamrgvap)hyibeuetacaxrecvci1tgahene0uon0ne8nbrtfieaddne0ytgehnee

liquids which may spray out from the flask.

temperature at which they begin to melt and theTtehmeperCatuorerkat fwahcicihlity isTahe spterrcaetnetaggiecyigeldloisbaa lgonoedwindpicartoordouf cthte ipnutrritoy dofutchetioinintial

How is crystallisation used in industry? they have all bottle of pure

e.oAmnpoathreertmhiesthvaoldueofwchitehctkhsineigtvteahleuemwefoilttuihnngdinpooninGtthoSef K's

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crystals is to use a narrow capillary tube in an oil baatuh.tTohemcaaptielladry tmubae nufaclottuofriimnpguriftiaesc. ility, as well as an R&D Pilot Plant

The

use

of

crystallisation

in

the

pharmaceutical

has one end open and the other end sealed.

indinutosfitnrey cisrysatanls iomf tpheosrutbasntatnce and the

tTuhrneweodpiteuhnpsePidniedloidstopwPrnelsaasnenddt

Laboratories

on

site.

process for controlling the physical properties, yield and purity of an

We are currently the primary production site for a number of

Active Pharmaceutical Ingredient (API). Many production processes

GSK's top selling drugs which treat illnesses such as depression,

use crystallisation in the final stage of manufacture to achieve these

Type 2 Diabetes, Congestive Heart Failure, Ulcers, HIV, Ovarian

targets. Recent advances in crystallisation process monitoring allow for

Cancer, Breast Cancer, Parkinson's Disease and Arthritis.

a better understanding of the process. These advances allow crystals with specific physical properties, for example particle size and shape, to be created. It is possible to produce crystals of varying particle size, shape and form polymorphs of the same substance, but only one will be

GlaxoSmithKline also has a manufacturing and R&D facility in Dungarvan, Co. Waterford and sales and marketing functions in Dublin. GSK currently employs over 1,400 in Ireland.

suitable for drug development and manufacture.

In industry, the way an API is filtered and dried can have a very significant impact on the physical properties of the material.

Calculating the percentage yield

After the crystallisation process the amount of sample will have been reduced as impurities have been removed. To calculate how much of the pure substance was present in the initial impure sample, the percentage yield is calculated.

Percentage yield = Mass of pure sample (after recrystallisation) x 100 Mass of impure sample (before recrystallisation)

The percentage yield is a good indicator of the purity of the initial sample. A high percentage yield implies a low concentration of impurities, whereas a low percentage yield indicates a sample with a lot of impurities.

You can find out more about the work of GlaxoSmithKline at , worldwide/ie.htm or at sta.ie

Glaxo comp the s a lea infect nervo The comm qualit to live World manu Curra the a facilit in de chem The C site w autom with P We a GSK' Type Canc Glaxo Dung Dubli

You Glax www

of and

of of its

and

Recrystallisation Benzoic Acid Determination Melting Point

Recrystallisation Benzoic Acid D

Producing pure substances is a very important process, especially in the pharmaceutical industry. Separating insoluble solids from solvents is easily achieved using a simple technique called filtration. Soluble solids again are easily separated from solvents by evaporation, and chromatography is used to separate a mixture of liquids. But what happens when we have two soluble solids that we want to separate? In this lesson we will look at recrystallisation, a commonly-used process in the pharmaceutical industry.

WShayt lislarebcurysstaRlliesafteiorne? nce

Recrystallisation is a very important purification technique, purifying

subLsetanacevsinbygreCmoevrintgifiuncwaantteed Cbyh-preodmucitss. tItryis also used

to manufacture the correct crystal size and shape of a material.

ThUesne itfa7c.to2rs? cPalnanhaavre Caarvberoy nsicgnoifimcapntouimnpadcst on how a

medicine acts when taken by a patient. The same principles and

tinedcJhunsutiqrynuseicsoaolerf .reCcryestratlliisfiaticonactaen beSacppileiednbcoteh on a laboratory and

Fig.1 Filtration to remove insoluble impurities

Fig.1 Finding the melting

tapped sharply against the desk causing the crystals to

point of benzoic acid

fall to the sealed end. When

Beaker containing benzoic acid dissolved in minimum amount of boiling water

Thermometer

about 3 mm of crystals are in the base of the tube it is placed in the oil bath. The

temperature at which the

sample begins to melt and

Filter funnel with fluted filter paper to speed up the filtrarion process. Insoluble impurities left behind as residue

Benzoic acid crystals Aluminium block

Practical Activities

the temperature at which it is completely melted are recorded.

To double check your result, mix a sample of benzoic acid with some

Conical flask with hot concentrated

pure benzoic acid. If both

benzoic acid soluMtionawnhicdh astitll ocorntyainEs xperimeBnuntse?n bLurneeraving

soluble impurities

Certificate are pure benzoic acid the melting point will remain

Recrystallisation of benzoic acid and determination tioshefnisotatsmpemubreeutltbiifentnhgzeoispcaomaipcnildet.

Boil

about

100

cm3

deionised

water

in

a

suitable

then the melting

bebaekloewreraend.d at

point

the

will

same

Section 2A7 ? Water and solutions What are the principles behind recrystallisation?

The process depends on two principles; the fact that substances tend to be more soluble in a hot solvent than in cold solvent, and that each solute tends to behave as though it were alone in the solvent.

time place a conical flask with about the same volume of boiling water Fig.2 on a hot After cooling, the remaining solution is filtered off plate. Into theHnoecwkdoof tIhkisncoowniIcahlaflvaesak ppluarcee sauflbustetadnficltee?r paper

Pure benzoic acid cystals

and wet the filter paperTwheimtheltbinog iploiningt owf aasutebsrt.aTncheeis nboot tihlienegxacwt paotientraitnwhtihcheitcmoelntsical

keeps everything warmbunuattirnlaittdhheasrsttchooemprapsnlgepeteorlyef tmemmelpateetdrua. Ttruhereesrgefrreocamtreywr sthheteanrtalhlniesgseaatmthiepolmenso.sretairmtsptuormitieelst

B?chner funnel

present. A range of less than 1 ?C indicates a pure substance.

Dissolve 1 gram of impure benzoic acid in the minimum amount of boiling

How do I know what solvent to use?

Learning Objectives Using the correct solvent is a very important part of the process. The

solute must be insoluble in the solvent at room temperature, and as the temperature of the solvent increases, the solubility of the solute also increases. It is also important that the impurities present are soluble in

theOsonlvecntoatmroopmlteemtpienragturethanidsinssoleubcletaitohingh,erttehmepersattuuresd. ent will be able to:

water and leave it on theHhoowt pislacter.yEsmtaplltiystahteiobnouilisnegdwianteinr fdroumstrthye?conical flask and replace the flTahsekusoe nof cthryestahlliosattiopnlainttehe. pImharmmaecdeuitaictael ilnydufislttrey irs athn eimpboertnanzt oic acid solution into the copnroicceassl ffloar csokntirnollsinmg tahellpahmysiocaul pnrtosp.erItfieas,nyyielcdraynsdtpaulrsityfoofrman on the paper use tiny amouAuscnetivtcesryPoshtfaalbrlmisoaactiileoiunntigcinalwthIenagtfirenedarlietsnottagd(AeiPsoIs)f. moMalvanneuyfatcphtrueordemutco.tioTanchhpiiesrvoepcetrhsoesescesess will have removed all thtaergientss. oRelucebnlteadivmanpceusrinitcierysstaflrliosamtionthpreocbesesnmzoonitiocrinagcaildlo.w for

a better understanding of the process. These advances allow crystals

An excellent substance for showing this process is benzoic acid

(C6H5CO?OHR). eAcmooglecnuilsarecrtyhsteal irmathperotrhtaannanceionoicfctrhysetalr,eshcorwynstallisation process

The B?chner flask filtrate is then powtouitbrheescdpreecaiitfinecdto.phItyiassicpaowlspsariborlpmeetrotiebpsreo, dfaourkceeexcarrmyasptlnaelsdpoafrttvihcalreeyisnigzwepaaantrtedicrlsehsgaipzeee,,ntly

by its low melting point of 122 ?C, benzoic acid is used as an anti-

manicdrodbeioa?dl oagraeUnnttsna. dndeirssfotaunnddintthooethpparsintecs,ipmoleutshwbaeshhesin, cdosrmeectircys stallisation

Water coenvtaianinpgosorluablteeimdpuruitiens til

tracesshaopef acndryfosrmtaploslymboerpghsinof tthoe saampepseubasrtanocne, btuht oenlysoidneewioll bfethe suitable for drug development and manufacture.

beaker. At this point you have a hot saturated solution of benzoic acid

In industry, the way an API is filtered and dried can have a very significant

Impure ?benCzoaiclcaucildatceontthaienspteherciemnputaritgiese yphiethladlicoafcaid saanmd ple after recrystallisation

so when the solution iimspaccot oonltehde p,hcysricyasl ptarolpserotiefs obfethnezmoatiecriaal. cid will come out

bhimoepnt suzoyrilltbviee?esnn,tzt?ohOaeinterute.hsItifsultihlcnteianesigmetspbhouoleruielitnisorgaonmwwleapitlleleocriso?fndartinseadsincofildrlvtyieesdrsseoitdnlavtaeolmdlriesibnmaeimnotzvaiooel viicnnosaluiocnmliudebianolesfdustryHouorwscuabnstwanecceh?eck

the

purityofosfolution. Cool the solution by placing the beaker in an ice bath ? the lower the temperature tChaelmcuolraetibnegntzhoeicpaecridcewniltlacgoemyeieoludt of solution and

well as dissolved impurities.

Upon co?olingM, tehae sbeunrzeoicthaceidmcreyslttainlsgcopmoesinotutooff csorlyutsiotnaalss iutssing

solubiluty in the solvent decreases. The impurities will remain in solution

tAmthheaeplnutsortehouesvuteplbriunsarteeawnsdicudebepshrtraaaosnngccaeeefi. oxTdefhduteermmmeepeletlitnrinaggtuprpoeoisnintatwnstchdohialfaeeatnalamngboliormseewtpeaauerlrtletneesusmrcubopybsestuoartaanrutncaurcergeesyeiedldbyArpweufdtsireluecrlcstrebuhadbeepasc.tsarinyiInmfscgtpeatuhlwltrisiheataiseetispcorhnrieanyspvessernoitbtdcaeieneelssntshoretdehfimenoiottanhivame'letdoim.ufflTpnootaurcrosemafklsscaauimwmlmapptieltmleehh, otwehwaiedllmphigeauarclvtcaheeesonlbytfseatgehtneerhoedy.

and can?be fiIldtereend otiff.y crystals using melting point data fromaretaavbaillaebsle.in tables.

Remember that in any ypieuldriisficcalacutilaotend.process you are going to lose some of

It is very important when carrying out this experiment that rubber gloves

To check the melting point place a few crystthalseosf tuhebssatmapnleceon yanou wanPetr.ceFntialgteeyrielod f=f tMhaesssoef pucrersyasmptalel(safteur rsecinrygstallvisaatcionu)umx 1fi0l0tration

are worn, because organic substances can be absorbed through the skin, and as well, goggles should be worn to protect your eyes from hot liquids which may spray out from the flask.

atolumheinaitumtheblbolcokckwhsliochwlhy.asWaattchhertmheomcerytesrtailnisfsecpratoreedsf.usllUyibsaelneda. hnAootntepyltahtseeoluble impurities tMhaasstoaf imrepuriensatmhpele (sbeofolrue rteicorynstawllisialtliosn)till be fully temperature at which they begin to melt and sthoeltuembpleeraitnurethatewhcicohld waTtheer paerncedntasgoe ythieledyis wa iglloopdaisndsicathtorr oouf tghehptuhritey ofifltteher inpitaiapl er.

General Learning Points

they have all bottle of pure

e.oAmnpoathreertmhiesthvaoldueofwchitFehcitknhineagvltlahyleuemwefoaltuisnnhgdpotonhinetthoefcrystasimalsmpupurlietsi.eisnA, gwhhitgeirhneaypseaarcmleonwotapugeenrctyesinetloadgfeimiycpieeliledscinoadlicdloawtewscaaotnescaremntptorlaetirwoenitmhoafove

crystals is to use a narrow capillary tube in an othil beatlha. Tshtetcraapcillaersy tuobfe the imlopt ouf irmitpieursitiefsr.om their surface. The fact that the water

has into

one fi ne

end open and the other end sealed. crystals of the substance and the

itTsuhrneiceodepeucnposeidnlded

idmsopwerneasasnnesdd

that

it

will

dissolve

the

minimum

amount

of

benzoic

acid.

? Different separation techniques are used depending on nature of

Dry the crystals on a filter paper. Weigh the crystals and calculate your

solutes and solvents.

percentage yield.

Glaxo comp the s a lea infect nervo The comm qualit to live World manu Curra the a facilit in de chem The C site w autom with P We a GSK' Type Canc Glaxo Dung Dubli

You Glax www

? Filtration can be used to separate insoluble solids from solvents.

? Evaporation is used to separate soluble solids form solvents.

? Recrystallisation is used to separate soluble solutes from a mixture of them in solution.

? Benzoic acid is used as a microbial agent in toothpastes, mouthwashes, cosmetics and deodorants.

? Melting points are calculated to identify substances and to verify purity of samples.

? Recrystallisation is widely used in the pharmaceutical industry to control physical properties, yield and purity of Active Pharmaceutical Ingredients.

? When choosing what solvent to use, remember more-polar compounds require polar solvents, where less-polar compounds require less polar solvents.

True or False

Indicate whether the following are true (T) or false (F) by drawing a circle around T or F.

(a) Separation is used to separate two insoluble solids.

T F

(b) Recrystallisation is a purifying technique.

T F

(c) An impure substance has a fixed melting point.

T F

(d) Organic substances tend to be less soluble in a hot solvent than in a cold solvent.

T F

(e) A range of 1 ?C in melting point of a substance indicates a pure substance.

T F

(f) Benzoic acid is an ionic crystal due to its high melting point. T F

(g) Polymorphs are substances with similar molecular composition but varying crystal structure.

T F

(h) A saturated solution is one which contains more solvent than solute.

T F

(i) The percentage yield is the mass of the pure sample divided by the mass of the initial sample.

T F

(j) Recrystallisation is used to produce crystals of specific size and shape.

T F

Check your answers to these questions on sta.ie

of and

of its

Recrystallisation Benzoic Acid Determination Melting Point

mental Monitoring

Producing pure substances is a very important process, especially in the pharmaceutical industry. Separating insoluble solids from solvents is easily achieved using a simple technique called filtration. Soluble solids again are easily separated from solvents by evaporation, and

Fig.1 Filtration to remove insoluble impurities

Beaker containing benzoic acid dissolved in minimum amount of boiling water

Fig.1 Finding the melting point of benzoic acid

Thermometer

tapped sharply against the desk causing the crystals to fall to the sealed end. When about 3 mm of crystals are in the base of the tube it is placed in the oil bath. The

chromatography is used to separate a mixture of liquids. But what happens when we have two soluble solids that we want to separate? In this lesson we will look at recrystallisation, a commonly-used process in the pharmaceutical industry.

WEhxataismreicnraysttiaollinsatQionu?estions

Filter funnel with fluted filter paper to speed up the filtrarion process. Insoluble impurities left behind as residue

Benzoic acid crystals Aluminium block

Did You Know?

temperature at which the sample begins to melt and the temperature at which it is completely melted are recorded.

To double check your result, mix a sample of benzoic acid with some

Recrystallisation is a very important purification technique, purifying

Conical flask with hot concentrated

pure benzoic acid. If both

suJbustanncieosrbCy reemrotviifingcuantweant2ed00by5-p,rodTuectcs.hItnios laolsogyuse-d Higher

benzoic acid sol?ution Twhhiceh sitnill vcoenntatinios n of the bBautntseenrbyurnbery Alessandro Voltaare ipnure1b8e0nz0oicparcoidvitdheed

to manufacture the correct crystal size and shape of a material.

ThSeesectfiaocntorBs ,cQanuehasvteioan 2very significant impact on how a

soluble impurities curious experimenters with a source of steamtdheeyltsinagmeelpebocuintttrifiwcthilel csraeummrparilene nt

mte(cechdoniciqinnueceesacorntfsrienwcrghyesnttahltleaiskaedtnioenbscyiagannbpeaatainepnpdtl.iefdTuhbneoctshtaiomonena ploarbifnoctriwaptloeorsydaannifddferent potential dividers) inSduesctrytisocnaleC. , Question 4

whose properties they explored. During the 19th ics ennottupruyre mbeunczohic oafcitdhe then the melting point will

basic theory of electricity was developed and mbealnowyeraedp.plications of

(concerning robotics, remote control, sensor feedback in relation to the

electricity were invented: electromagnet (1820), electric motor (1821),

WrMehcaarrytssaLtraaenllditsheaer)tipornin?ciples behind

Fig.2 theory After cooling, the remaining solution is filtered off of electricity gHeonwerdaotioInk(n1o8w31I),healevcetraicpliugrhet (s1u8b7s8t)a, nfircset?power

Pure benzoic acid cystals

station (1879), first hTyhde rmoeeltinlegcptorinict opf aoswubestranscteaistinoont th(e1e8x8ac2t )p,oifinrt sattwahlicteh ritnmaetltisng

The process depends on two principles; the fact that substances tend

toJbue mnoiroe rsolCubele rintaifihoct saoltveent2th0an0in4c,olTd esoclvehntn, aondlothgat yeac-h Higher

solute tends to behave as though it were alone in the solvent.

A student is required to produce a circuit which will turn on a water pump

current generator (18bunu8tti8rlai)tth,heaersltcheoecmratprnligeceteiotlyyf tmedmeilptseetdrra.iTtbuhrueesgtifrroeoanmtewsr thyheesnrttaehnemgseatm(h1ep8lme9sos3reta)ir,mtseptuloermitcieetlstric B?chner funnevl acuum cleaner andprewseanst. hAirnanggemofalecsshtihnaen 1(?1C9in0d3ica).tesAallputhreesusbestadnecev. ices are

classed as electric.

HwohwendolowI kwnaotwer wlehvealtssaorlevednettetcoteudsbey? a sensor. UTsinhgethceocmorrepcot snoelvnenttsisliasvteerdy imbpeolrotawnt paarret oaf tvhae iplarobcelses.tToheconstruct the circuit. solutLe EmuDst bSeeinnsosluobrle iTnrtahenssoilsvetnot ra,t rRooemsteismtpoerrat2urKe,2a,ndRasetsheistor 330R, Motor (pump), tinecmrepVaesraaetrsui.raIetbioslfeatlhsreoesimsoilpvsoetrnottarni,ntc9trheVaatstbehsea, itmthtepeursryoitileusbiplitryesoefntthaeresosloultueblaelsion

the solvent at room temperature and insoluble at higher temperatures.

A1n .eUxcselilnengt sthubestasnecne sfoorrsahnowdintghtehisvaprroiacebslseisrebseinszotoicr,ascikd etch the circuit diagram for

How is crystallisation used in industry? ? The invention of the dThioe udsee oinf cr1y9st0all4isactioonuilndthbe ephdaremsacceruitbicealdindausstrtyhies abn eimgpionrtnanint g

of electronics. Unlpikroecesws fiorrecso,ntroellliengctthreicphylsigicahl tpsropaerntieds, yeielled cantrdopmuriatygonf aents,

diodes conducts eleAusccetitvrceircyPsihttayalrlmisinaactieoountnicinealthdIenigrfirenedaclietsnitotagn(AePooI)fn. mlMyaannuayfancpdtruordethutcoetioiarnchopieprvoeecetrhsaestesieson cannot be adequatetlayrgeetxs.pRleaciennet addveanxccees ipn tcriynstatellisramtiosn porfoceelsescmtornoitnorsin.gAallnowotfohrer

development

B?chner flask

along awthibtheetstepsreacuinmfidceeprshtlyaisnnicdeainlsgp,rootfphteheretieptsrro,iocfoedrssee.x,aTmheepnsleeapabdalrvetaicnslceewssizeaelaloakwndcssryihgsatpnaelas, ls

b(Cy6iHtst5hCloOewOpmHo)e.lttAiengmnotpiloaeicnlutdlaoirfvc1ird2y2seta?rCl r,raebthqeenurzotihricaendacainidnioisnthiucsiscerdycsaitsarcl,ausnhiaot.nwtnim2ic.roNbiaal mageentaannddisefxoupnldaiinntoyoothuparsctehs,omiocuethwoafsmhesa, tceorsimaeltifcosr the sensor.

to be amplified. Thestoebevcarecauteud.mIt itsupbosesibdleiotodperosduacne cdrytsrtiaolsdoef vsary(iongr p`varaticlvleessiz'e,as Water containtihngesoylubwle eimrpeuritciesalled) wessruheiataptbehleaenfodbrfodurrmiulgdpdionelyvgmeloobrpplmhoseconkft tashnedosmaf maeneluesfuacbcttsrutoarenn.ciec, bsuft oonrlyaobneowuiltl bfiefty

and deodorants.

3. Explain why a variable resistor is used in the potential divider.

years.

In industry, the way an API is filtered and dried can have a very significant

Impure benzoic acid contains the impurities phthalic acid and

impact on the physical properties of the material.

bhimoe4pnt.suzoyrtIinhlltbvieedeesnni,tzcpt?ohaoaeinttteretee.hsIinfsucthltctlieiaeansigamlesrdpboluoyilruvielitiniwsdoganehmwwriap.citllelehcriso?pndatinsiandsinosfildlvtieesodrsenoidnlvtateohmdreeibnmeimnovzvaaoel rviicnioasaluocbmliudleebaolesfresistoHoruosrwhsocuuablndstwbaenecucesh?eedckinthe

purit?y

oSf olid-state semiconductor devices began to replace valves 1950s--crystal diodCeaslcaut filarstitnagndthterapnesriscteonrstasgoemyeieyledars later.

in In

the the

well as dissolved impurities.

A pure substance has a fixed melting point while 1an9i6m0pusrethsuebsfitarnscte integrAafteter tdheccirrycstualiltissatcioan mproeceossnthtehaemmounatrokfestamapnledwiilnl h1av9e7b2eetnhe

Junior Certificate 2001, Technology - Higher Upon cooling, the benzoic acid crystals comes out of solution as its

solubiluty in the solvent decreases. The impurities will remain in solution

melts over a wide range of temperatures and atfiarslotwcerotemmmpereartucreial micrreodupcerod acseimspsuoritriecs hhaivpe bweaensrermeolevead.sTeodca.lculate how much of the

than the pure substance. The melting points of almost all substances

pure substance was present in the initial impure sample, the percentage

anSdeccantiboenfiltBer,edQouff.estion 2

are available in tables.

? Although the distincytiieoldnisbcaelctuwlaeteedn. electric and electronic devices is not

It(iscvoernycimepronrtianngt whtehn ecarrdyinegsoiugtnthis aexnpderimoenpt teharat rtuibobner golovfesa

are worn, because organic substances can be absorbed through the

temTaolpumcehirneaicuktmuthrbeelomckealwtlianhgircmhpoh:ianst apanlathceerma ofemwetcerrysintaslesrstoehfd.taherUpsse,amathphleeotowpnlaoatnerd elecPterrcoenntaigce yisieldn=oMwMaaassssdoofafimpyupsruerseuasmsampulpeal(eall(fbyteerforrereecrsryesectraryllvsisteaaltlidiosnat)fioon)r xd10e0vices

skininc, aondmaps wleetlle, gocgigrlcesusihtoudldiabge wraormn towproatsectgyoivureenyesafrnomd hosttudenttoshewatetrhee beloxcpk eslcowtelyd. Wtaotch the crystals cawrehfuollysaendonpoteertahteion depends on solid-state semiconductors. On this

liqcuoidms wphlicehtemaiyt sapnrady oeutxfprolmaitnhe hflaoskw. it functioned.)

temperature at which they have all melted.

they begin to Compare this

mvaellut eanwdiththethbteeamvasplueiseraftaouurnendaotorwndhtiihcnheary

elTseahcmetprplieec.rcleAanmthaiggpeh

yipsieelrd`ceeilsnetaacgtgeroicoydi'elbdinudiimctapittloiercsoofauthlldoewpbuceroitnyacoergfntturhaeetiodinnittioahfl at

bottle of pure substance. Another method of checkiangCtheFmLelltainmg ppoinitsof`electrimopnuirciti'e.s, whereas a low percentage yield indicates a sample with a

2001

Junior

Certificate

Technology

Higher Level crystals is to use a narrow capillary tube in an oil bath. The capillary tube

has into

one fi ne

ecnrdysotaplesnoaf ntdhethseuobtshtaenr ceendansedatlehde?. tTuhrneeTodrpaeunnpsseidnised tidosoprwsrnesaasrneedd

the

lot of impurities.

active components

in

many

`transistorised'

devices

The sketch shows a circuit for a high temperature alarm.

such as radios, tape recorders, etc. Increasingly they are integrated

(i) Identify the components `X' any `Y'

into more complex `chips'. The transistor is the solid state successor

State the purpose of component `Y' in the circuit.

to the triode valve and following its invention it gradually replaced the

S1 +9 V

vacuum tube in most applications. The invention is usually attributed to William Shockley, John Bardeen and Walter Brattain who in 1947

Z

X

R

produced the first practical transistor device. However similar devices had been described in 1928 and 1934 but it seems that they were not

manufactured. In contrast to the triode, the transistor is a solid device

and its invention marked the beginning of solid-state physics.Today

transistors are the basic subunits in most integrated circuits (ICs or

Y

`chips') including microprocessors.

0 V

Why is a transistor used in this circuit? How can the cathode of the LED be correctly identified? (ii) If the maximum permitted current for the LED is 0.02 A, show how to calculate the value of the resistor `R' required for the circuit. Which of the following values should be used for resistor `R'?

270 , 330 , 390 , 470 , 560 , The fourth band in a resistor is either silver or gold. What does the colour of this band indicate? (iii) Name and sketch the symbol for the component which should be located at `Z'.

For further examples of past paper questions check sta.ie

Revise the Terms

Can you recall the meaning of these terms? Reviewing the terminology is a powerful aid for recall and retention.

Electricity; electric circuit; current; voltage; battery; switch; automatic; sensor; component; thermostat; bimetallic strip; temperature; pressure; humidity; potential divider; in series; resistor; resistance; electronic; thermistor; LDR; calibrate; speaker; microphone; electric motor; electric generator; transducer; volt; millivolt; computer; operating system; computer network; ad hoc network; mote; wireless communication; pH probe; chemical sensor

Check the Glossary of Terms for this lesson at sta.ie

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