Purity analysis of highly purified materials by time-temperature cryometry

Ross, Gaylon S.; Dixon, Herbert D.

doi:10.6028/jres.067a.025

Cited by 7 publications

(5 citation statements)

References 5 publications

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“…Two difTerrent samples of benzene were a nalyzed . In t i1e first saillple the purity as determined by t he m ethod described he rein was co mp ared wi th t he plll'ity as determined by t ime-temp erftt ul'C a nalysis usin g a 50-ml sa mple [2,3]. vVhen th e second sample was analyzed a portion of the sa mple was placed in the small, gold-van ed cell a nd a nother identical portion was distilled into an all-glass cell, similar in shape and size.…”

Section: Methodsmentioning

confidence: 99%

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Principles of cryometric impurity determination as applied to samples of small sizes

Saylor¹,

Ross²

1964

J. RES. NATL. BUR. STAN. SECT. C. ENG. INSTR.

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A co nsideration of the faclo rs that tend to prevent attainmen t of t hermal a nd t hermod.vna mic1equ ilibrium d ur ing t hermometri c m etl;ods of purity an alysis s uggests t lmt t he p r o~1 ems. la rgely o n glll ate from sp onta neously. llltr oclucecl inequali ties i n com p os it ion . D un ng eit her a fr eeZin g or m el tlllg cycle, t he soh d phase settl es in t he liqu id. T his r eslil ls i n a greater a \'er age puri ty i n the boLlo m t han in t he upper part of t he \" esse!. TIle effecls would be par ticul a rly s trong duri ng a melling sequence \\ 'here the liquid released by melting of t he solid " -ould prov ide t he co mpositio n al en vironm ent for t he establis hment of fin a l temperature. This hyp ot hesis has been tested by t he des ign of a new cell f or s mall samples. The dcsig n inco rp orates use of s mall go ld p a ns to hold solid and liqui d in close contact. T he resul ts are co mpar able i n precision Lo t hose from conventional t i me-temperature curves witll muc h la rger samples, a co nd iLion not ordinarily p os ible wit h small samples.

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Section: Methodsmentioning

confidence: 99%

“…The results of t hese analyzes were, respectively, 99.985 a nd 99.980 mole percent. vVben 50 ml of the sample was analyzed thermometrically [3], the purity was calculated to be 99.976 mole percent.…”

Section: Methodsmentioning

confidence: 99%

Principles of cryometric impurity determination as applied to samples of small sizes

Saylor¹,

Ross²

1964

J. RES. NATL. BUR. STAN. SECT. C. ENG. INSTR.

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“…The two other techniques effectively depend on heat content. They are adiabatic calorimetry [3, 4] and time-temperature (thermometric) freezing curves [5, 6]. A carefully conducted comparison [7] has shown that the three techniques, each at its best, can give reliable results.…”

Section: Cryometric Methodsmentioning

confidence: 99%

Chemical purity by dielectric cryometry

Ross¹,

Frolen²

1963

J. RES. NATL. BUR. STAN. SECT. A.

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A co ns ider at io n of th e defi ciencies in standa rd methods used for t he cr yometr ic clrt(' rmination of puri ty has led to a new a pproac h in w hi ch t he m eas uremen t of an in t('n siv(' r ath er t ha n a n extensive proper ty is t he contr ollin g fa ctor. This m ethod , m easu re men t of t h e di electri c con stan t as a fun ction of t he fractio n melted a nd correlation w ith t h e acco mpan y ing change in te mperature, allows calculat ion of puri ty w it h hi gh precision. Th e a pparat us used a nd ex perim en tal work p erform ed t o ascer ta in t he sco pe of t he m eth od a re desc ribed. Dete rmin at ion of puri ty fo r o rgani c co mpo nnds wit h differin g polari zabilities a nd dipol e moments indicate a rat her w id e a ppli ca bili ty o f t he m ethod . The la rge eha nge in t h e d ielectric co nstant of a hi gh p uri ty co mpoun d as it p asses fr o m solid t o liquid sta te, with a n acco mpa ny in g small chan ge in te mperature, may allow a u to matic con t rol of t emper at ure wit hin extre mely n a rrow limi ts . Cryometric MethodThe well-known m ethod or freezing poin L depression, (T Jo-TJ) -wh ere TJO is the freezing point of t he pure ma teri al and T J t hat or the ac tual sftmplepro vides a sensi ti\T e nond estructive m easure of impuri ties. In t his method a pb ysical proper ty, ~, is determined as a IuncLion of Lempera ture, Tx, in. the region or tbe liquid-solid transition . Th e liquid frac tion, F, is presumed to be a linear function or ~, tha t is:For nearly pure substances the gener alized van 't Hoff equation applies:1:,N t designates th e sum of the mole fractions of impuri ties soluble in th e liquid and insoluble in t he solid. Conventionally it is written N 2*' .6. H f is the molar h ea t of fusion of the pure m aterial. R is the gas constant. The factor .6.HJ/RTJo 2 is generally r eferred to as the cryoscopic constant, A, and (TfO -Tx) is equated to .6. T so tha t eq (2) can be written :Where N l* is the mole fraction of tb e major component. On r ewri ting (3) w e have the straight line r elationship : (4) Wh en F = l , Tx= Tf> the m el ting poin t of the sample by defini tion. When the line is extrapolated to F=O , Tx= TJo , so tha t by th ermodynamic t h eory applicable to dilute solu tions the m elting point of t he pure subs tance can be deri \'ed exp erimentally from a plot or ~ vcrsus T x. In practice cxp erimen ters of ten derive T fo by extn1.polation of Lh e hypcrboli::: r elation (3) to p=o.Presen. L ly t here exist Lhr ee widely used cryomeLric tcchniqu cs. In d ilatometry [1 , 2] 1 the sample volume is t he physical prop er ty~. Th e t wo other techniqucs eff ec Li vely depend Oll h eat con ten t . They ar e adiab atic calorimetry [3,4] and timetemperature (thermometric) fr eezin g cur vcs [5,6]. A car efully conducted comparison [7] h as shown tha L Lhc Lhree tec hniqu es, cach at i Ls b esL, can gi\Te r eliable r csul L. Th e chief acl\ran tage in t be caIOl'im etric approac h is Lbat 011 C direcLly ob tain s accurate values for hea ts of ...

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“…Pull details of the method were disclosed at the EURATOM Conference on High -Precision Analysis of Substances of Interest to Nuclear Chemistry, January [18][19][20][21][22]1965 [8] , and will be published in the near future.…”

Section: Facilitiesmentioning

confidence: 99%

“…The purity values of the presently available NBS standard reference materials of hydrocarbons were obtained by this method. Examples of more recent results and comparisons of this method against the other cryoscopic techniques have been published [18,19].…”

Section: The Cryometric Cell Is Described In Detail By Glasgow and Tementioning

confidence: 99%

Analysis and Purification Section :

Taylor¹

1965

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Stills used for preparation of ultrapure reagents ..... 25. Extractor for purification of silica gel 26. Quartz container for dispensing purified reagents 27. Physical arrangement of the major facilities for light-element purification 28. Three-compartmental assembly for high-temperature experiments with toxic materials 29. Cabinet area of assembly for low-temperature trap, absorption tube, and fore-pump 30. Three-zone furnace, automatically controlled, for hightemperature phase separations 31. Front and back views of electronic units for automatically controlling and recording temperatures in the three-zone furnace 32. Controlled-atmosphere glove box 33. Phase purification and thermal analysis cell ... 59 34. Assembled cell for use at 1000°C in phase purification 60 35. Disassembled cell for use at 1000°C in phase purification 61 36. Rupture-disk ampoule 62 37. Manifold used to fill rupture-disk ampoule .... 63 38.

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Purity analysis of highly purified materials by time-temperature cryometry

Cited by 7 publications

References 5 publications

Principles of cryometric impurity determination as applied to samples of small sizes

Principles of cryometric impurity determination as applied to samples of small sizes

Chemical purity by dielectric cryometry

Analysis and Purification Section :

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