Simultaneous measure ments are described of specific heat capacity, electrical resistivity and he mispheri cal total e mittance of the ternary alloy 90Ti-A I-4V in the tempe rature range 1450 to 1900 K, and the melting point and and the radiance te mperature at the melting point of the alloy by a subsecond duration transient technique .The results are e xpressed by the relations: c p = 1. 3833 -9.943 X 10-4 1' + 3.745 X 10-'7'" p = 152.65 + 1.9304 X 10-2 1' -3.9548 X 10-6r' whe re Cp is in J. g-" K-' , P is in ,.,.n .c m, and T is in K. Th e valu e of th e hemis pherical total e mittan ce is 0.39 in the ranl';e )700 to 1900 K. Th e me lting point and the radiance te mperature a t the me lting point a re 1943 and l796 total emittance of the ternary a lloy 9OTi-6Al -4V in the tempe rature ra nge 1450 to 1900 K, and the melting point 0.395.Estimated maccurac ies of measured prope rti es are: 3 percent for s pec ific heat capac ity, 1 perce nt for electrical resistivit y, 5 percent for he misphe rica l total emittance and 8 K for melting point and radiance te mperature at the me lting point.Key words: Electrica l res istivit y; heat capac it y; high-speed measure me nts; hi gh te mpe ratures; me lting; normal spectral e mittance; radi a nce temperature; spec ifi c hea t ca pac it y; th ermal radia ti on prope rti es; the rmod ynami cs; titanium a lloy.
An e valua ted compil ation of equilibrium rela ti ve humiditi es in a ir ve rsus tempe rature from pure phase to a pproximatel y l OS pascal (1 a tm) in press ure is present ed fo r 28 bina ry saturated aqueous so luti ons .Th e relative humiditi es of th e solutio ns ra nge from about 3 to 98 pe rcent.Us ing a da ta base from 2 1 sepa ra te in vesti gati ons compris ing 1106 indi vidu al meas ure me nts, fits we re made by the me thod of least s qua res to regula r po lynomia l equ ati ons with two through four coeffi c ie nts.Equa ti ons a nd ta bles a re presented a long with the estima ted uncert a inti es in the correla ted res ults.
Two idealized models for the preheat s tage of liquid dro plets are ana lyzed theoretically .These models conta in the effects of transie nt heat conduction and e va porati on.It is assumed that the droplet surface a rea decreases linearl y with ti me.This assumption necessitates the soluti on of mov in g boundary pro ble ms .These models, howe ver, do not consider gas-phase mass transport .In the finit e-gradient model, the te mpe ratures of both the dro plet a nd s urrounding hot gases vary spatia lly a nd temporall y.In the zero-gradie nt mod el the gas tempe ratu re varies spatia lly and temporall y but the d roplet temperature vari es onl y tempora ll y, i. e., the drop let tempe rature is spati a lly uniform .Numeri cal e xamples, whi ch require exte ns ive ca lcu lations of connue nt hypergeometric fu nctions, are presented for typi cal va lues of the d ro ple t late nt heat and evaporation rate consta nt.The tem pe rature profi les give n by the fin ite-gradient and zero-grad ient models agree to within 20 percent of eac h othe r for a ll cases examined .
Rate coeffi cie nts for produc tion of sta bilized dime ri c parent cations at 295 K hav e been dete rmined in CH31.CD3l, C H3l -CD31 mi xtures, C, Hsl, C H3C D,l, CD3CH,l, a nd C, Ds l.These processes a re the most rapid re port ed for association reactio ns, the va ri ous individual va lues fa lling within the limits 0. 33 X 10-'4 (C H31) and 10.1 X 10-'4 c m 6 molec ul e-2 sec-I (C2 Hsl) .The temperature de pende nce of the stabili zation coeffi cie nt s in CH31 a nd C D31 was a lso measured over the range 220 ± 3 to 320 ± 1 K, as we ll as the e ffi c ienc ies of oth e r third bodies in th e s tabilizatio n process.The differe nces observed for the various ly la be ll ed analogues are inte rpreted in te rms of vibratio na l level (energy) depress io n upon deut eration , whi c h a ffects the intrins ic li fe tim e of th e co lli sion co mpl ex .
A qua ntita tive d esc riptio n is g ive n for the dens ifi cati on process of glasses resulting from g lass [orma ti o n at ele vat ed pressures .Phe nome n olog ica l re lati ons a re de rived, or j us tifie d , whic h al low es tim ati on of th e de ns ifi calion rate K ' (with respect 10 formation pressure ) fro m variolls the rmodynami c q uantiti es a nd glass trans ition be hav ior.In addition, the estimatio n of K ' may be fac ilit a ted by the appl ic a ti on of the hol e theory of S imha and Somcyn s ky.Using these relations K' is estimated , and the results from the d ifferent me thods a re co mpared for data from 23 diffe re nt organi c poly me rs wi th g lass tra ns iti on te mpe ratures rang ing fro m 150 to 455 K. T he a mount of de ns ifi cati on appea rs to be limit ed by the appa re nt convergence o f the glass tempe rature a nd e ffective decompos ition tempe rature wi th in c reas ing pressure .Some estimates of limiting values are presente d. final ly, c hanges of refrac tive index resulting from de ns ification are estima ted from the observed, or predic ted , de nsific atio n ra tes.
Solubility isothe nns of hydroxyapatite, Ca5(PO.hOH (OHAp) , pre pa red by titrating a boiling aqueous suspe nsion of Ca(O HJ, with 0 .5 M H3PO., we re detennined in the te rnary system Ca(OHJ,-H3PO.-H20at 5, 15, 25, a nd 3 7 °C in the pH ra nge 3 .7-6.7 by equilibration with dilute H3PO.solutio ns.The solubility product K" dete rmi ned as a fun ct io n of te mpe rature by a gene ra lized least-squa res procedure from 4 1 ex pe rimenta l points, is g ive n by the equation log K, = -82 19.41/ l' -1.6657 -0.0982 151'.The values of K s and it s dis persion at 25 a nd 37°C a re 3.04 (0.25) a nd 2.35 (0.27) X 10-59 .The re is a max imum in K s near 16°C, whic h may be d ue to the fo rm of te mperature de pendence found earlier fo r the sta bilit y constants of the ion pa irs Ca H2POt a nd Ca HPO~.The re lati ve pos itio ns of the isothe rms s how that OHA p has a negati ve the rma l coeffi cient of solub ility.T hermod ynam ic fun ctions for the di sso lutio n of the sa lt a re report ed .T he so lubility data previous ly re pOl1ed by others fo r OHAp at 25°C were rev iewed .The solubility prod uc ts obta ined by three of these in vestigators were compara ble with our value of 3 .0X 10-59 ; thei r data were reeva luated by the method desc ri bed he re.We conclude that the best value fo r the so lubility p rod uct at 25 °c is 4.7 (2 .0)X 10-59 .
A new fonn ulation is presenl ed for Ih e vapor press ure of ice from Ihe triple point to -100°C based on thermodynamic calculations.Use is made of Ih e d efinilive ex pe rim e nlal value of the vapor pressure of waler a t its triple poinl recentl y oblain ed by Cuildner , Johnson, and Jones.A tab le is given of Ihe vapor press ure as a function of le mpe rature at O.I-d egree inl e rv a ls ove r Ihe range 0 10 -100 °C, logel he r wilh Ihe values of Ih e lemperature derivative at I-degree inl e rvals .T he formu laLion is compa red with published ex perime nlal meas urement s and vapor pressure equaLi ons.It is eslima led Ih at Ihi s formu lalion predi cls Ihe vapor pressure of ice wit h an ove rall unce rtainl y Ihal vari es from 0.016 pe rce nl al the Iripl e poinl 10 0.50 percenl a l -100 °C.K ey wo rd s: C lausius-C lapey ron equation; sa turation vapor press ure over ice; th e rm a l properti es of ice; vapor pressure; vapor pressure at th e triple point; vapor pressure of ice; waler vapor.Pa Pa c m 3 / g c m 3 /g c m 3 /c m 3 Pa cm 3 /cm 3 Pa J/gK J/gK
Solubility isotherms of hydroxyapatite, Ca5(PO4)3OH (OHAp), prepared by titrating a boiling aqueous suspension of Ca(OH)2 with 0.5 M H3PO4, were determined in the ternary system Ca(OH)2–H3PO4–H2O at 5, 15, 25, and 37 °C in the pH range 3.7–6.7 by equilibration with dilute H3PO4 solutions. The solubility product Ks, determined as a function of temperature by a generalized least-squares procedure from 41 experimental points, is given by the equation logKs=−8219.41/T−1.6657−0.098215T.The values of Ks and its dispersion at 25 and 37 °C are 3.04 (0.25) and 2.35 (0.27) × 10−59. There is a maximum in Ks near 16 °C, which may be due to the form of temperature dependence found earlier for the stability constants of the ion pairs CaH2PO4+ and CaHPO40. The relative positions of the isotherms show that OHAp has a negative thermal coefficient of solubility. Thermodynamic functions for the dissolution of the salt are reported. The solubility data previously reported by others for OHAp at 25 °C were reviewed. The solubility products obtained by three of these investigators were comparable with our value of 3.0 × 10−59; their data were reevaluated by the method described here. We conclude that the best value for the solubility product at 25 °C is 4.7 (2.0) × 10−59.
Ve ry oft e n a non-so lve nl diffuses into a glassy polyme r with a steep co ncentration profil e proceeding a t an a lmost consta nt rate v yi e ldin g a we ight ga in proportio na l to time.S uc h a diffus io n is ca ll e d type II diffus io n in orde r to distinguis h it from the more usual "' Fic ki a n" diffus io n proceed in g witho ut su c h a constant conce ntra ti o n front a nd yie lding, at le ast in the beginning, a we ig hl ga in proportional to the square roo t of time .It turns out th a t the conve ntiona l diffus io n equation without a ny spec ial ne w te rm but with" diffus ion coe ffi c ie nt rapidl y inc reas in g wilh concentratio n has a seri es of solutions re presenting exactly suc h type II diffus ion with /} as a compl e te ly free pa rame le r whic h d e te rmines the stee pness of concentra ti on fro nt.With the us ua l bo undary condilions a nd infinite me dium Ihe diffus ion coe ffi c ie nl has 10 become infinit e a l Ihe highest pe netra nt concentration.Thi s case ca n be c ons ide red as an ex tre me limit whi c h is a pproac hed 10 a high d egree in a n a c tual ex pe rime nt.The finit e sa mpl e thic kness, howe ve r, requires onl y a ve ry la rge but not a n infinil e diffus ion coeffi c ie nt.He nce Iype II diffus io n is o nl y a s pec ia l c ase of poss ibl e diffusion processes compatible with the conve ntiona l diffu s io n eq ua ti on wilhout any need for ne w te rms if on ly the diffus ion coe ffi c ie nt inc reases s uffic ie ntl y fasl with pe ne tran l conce ntra tion . Key words : Concentration de
T he rece ntl y obtain ed c ompl e te so lution of Ih e s irn ult an eous diagonalizali on of matri ces H A a nd H in the hydrody na mi c diffu s ion equat ion has bas ic a ll y c han ged the diagona l va lues v" of the sy mme tri c malrix H of hydrod yna mic int e rac ti o n be lween a ll the beads of the e lasti c ra ndom c oil mod e l of th e iso la te d mac romo lecul e in soluti on.Si nce th ese va lu es ent er exp li citl y th e expression s for th e intrin sic stress and refracti ve in dex tensor in an a lt e rnating fl ow fi e ld if based on the conce pt o f inte rnal vi scos it y o f the model one had to reca lc ulat e a ll va lues obt a ined form erl y b y us in g the th e n ge ne ra ll y acce pt e d e rroneous se t of 11" data.Th e ne w vp e qua l uni ty independenl of p while th e old va lues were larger than 1 for small p and s ma ll e r for large p.He nce the ir too la rge contributi on s in th e fonn er range are partiall y compensated by th eir too small contributi on s in th e latt e r region.A s a c onsequence in the who le ran ge in vesti gat e d , be tween 3 and 3 00 c ha in link s, th e diffe re nces in rheo logica l and rhe oopti ca l e ffects are relat ive ly s mall, up to a fa c tor of 2, a lthough at hi ghe r link numbe r the diffe re nces le nd to grow wilh the logarithm of this numbe r.
A new humidity calibration facility whi c h uses the two-press ure prin c ipl e for gene rating gas of known humidity has been de veloped at NBS for calibrating and testing hygrome ters.The relat ive humidity range of the two-pressure humidit y gene rator is 3 to 98 percent for ambient tempe ratures -60 ° to 80 °C and test c hamber pressu res 5 to 200 kPa (abso lut e) .Thi s is equival e nt to a nomina l d ew/ frost poi nt ra nge of -80 ° to 80°C.Intercomparison tests we re mad e with the NBS sta ndard grav ime tri c hygrometer over a portion of the gene rator's opera tin g range.The estimated maximum uncert aint y (three sta ndard de viations) is 0 .2percent RH for tempe ratures 0 ° to 80 °C whi c h in units of d ew point corresponds to a n estim ated max imum uncerta int y of 0.04 °C for de w points -35 ° to 80°C.
Accurate measure me nt of s to ic hio me try of GaAs provides new d a ta whic h a re u sed for ca lcul ation of the atomic weight of Ga .Us ing the IU PAC accepted val ue fo r the a tom ic we ight of As (74.92 16).th e a tomic we ight of Ga based o n this work is 69.737 ± 0 .006 .The mean of two inde pe nde nt c he mical va lues for th e a tomi c we ight of Ga, one obta in ed by Lunde ll a nd Hoffm an a nd th e othe r in th is wo rk , is 69.735.
The stand a rd pH values or th e solutio n or potass ium hyd rogen phtha la te (mo la lil y 0.05 mol kg-I) have bee n red ele rmin ed ove r Ihe le mpe ralure range 0 to 60 °C, us ing S RM l 8Se1.Ext e ns ive meas ure me nts we re made or th e e mr or ce ll s or Ih e Iype Pd; H2(g, 1 a lm)J KH phlhal ale (rn = 0.05), KCI (ml JA gC I;Ag wh ere m.KCI was 0.015, O.OJ., or 0.005 mol kg-I, rrom whi c h va lues or th e acidil y run cti on p(a ,"Ycl) we re derived.The pH conve nti o n d efin es Yel in Ihe ra nge or ionic stre ngths 0 to 0 . 1 mo l kg-I a nd pe rmits co nvenlio nal va lu es or paH 10 be obl a in ed.According to NBS procedures, I)(lH ror se lected re re re nce so luli ons is idenlifi ed wilh Ih e s landard pH(S) in the ope ra ti onal de finiti o n or p H. The new va lues, give n in te rm s or Ihe the rm ody na mi c tempe ralure ( 7') b y 2073.44 pH(S) = --7'--13.3270+ 0.0451997' -3.4846 X 1O-' {' d irre r, on the average, by 0.003 unil rro m th e res ults based on th e 1944 data or Hamer and Acree .
The shear modulus G = 5.925 × 10−3(fp − 0.45)T+G* (Part I), its energy component G* = 0.0684 (fp − 0.45)+ 2.70 (Part II), and the number of effective suh-chains per unit volume ve= (G – G*)/RT are given detailed molecular consideration. G is given in Mdyn cm−2 for rubber cross-linked by adding p parts of dicumyl peroxide per hundred of rubber, and heating until a fraction f of the peroxide is decomposed. ve is found to be approximately twice the density of cross-links, after a correction for impurities and chain ends is made. It can not be computed as G/RT since only the entropy component of modulus is related to ve. The sub-chains for the most highly cross-linked rubbers studied had a molecular weight of about 575 g mol−1, corresponding to about 8 isoprene units. The modulus corresponding to no added cross-links is not zero. It is determined chiefiy by the energy component of the modulus; it does not arise from entanglements. The “front factor” is found to be unity. An extensive literature survey yields values of the quantity RTΨ(v2), where Ψ (v2) is the Flory- Rehner equation function of v2, the equilibrium volume fraction obtained by swelling the cross-linked rubber. RTψ (v2) is found to be greater than G – G* but not as large as G itself.
In connection with the work on development of a high resolution laser source bidirectional reflectometer, a large number of papers were collected dealing with various aspects of the geometrical distribution of the radiant energy reflected from surfaces of different types. Each paper has been classified into one or more classes on the basis of its technical content. There are eight general classes, with several subclasses in some of the general classes. Because of the interest in this field, the bibliography is being published as a service to the public.
A chemical model is proposed for describing charge-transfer complexes between aromatic amines and electron-accepting benzene derivatives containing a group having a double- or triple-bond conjugated with the benzene ring. According to this model, an electron migrates from the nitrogen atom of the amine to one of the atoms of the multiple-bonded group during charge-transfer interaction. Structure-property relationships were derived for correlating: (1), the transition energies of the complexes; (2), the ionization, or oxidation, potentials of the amines, and (3), the electron affinities or reduction potentials of the electron acceptors, with the electron-donating abilities of the substituents of the various compounds. Transition energies calculated from reported spectroscopic data for these complexes were correlated using equations derived in this study. Similarly correlated were reported data for the above properties of the amine and electron acceptor. Equations were derived for correlating the effect of variation in solvent on the transition energies of the complexes. Correlation of reported spectroscopic data indicated that the greatest effect is caused by variation in the refractive index; of secondary importance was the change in dielectric constant.
The energy levels belonging to the configurations 3d74s2 and 3d8nℓ (nℓ = 4s, 5s, 4p 5p, 4d 5d 4f, and 5g) have been calculated. The radial energy integrals were treated as parameters and adjusted to give a least-squares fit to the observed levels. Two- and three-body effective electrostatic interactions for equivalent electrons were included, as well as two-body effective interactions for inequivalent electrons. Strong configuration interaction between 3d74s2 and 3d84d was taken into account. Values of the parameters are given for all the above configurations, and the calculated levels are given for all except 3d84s and 3d84p (for which essentially equivalent results have been published). Leading eigenvector percentages are given in appropriate coupling schemes.
Four molecular fluorescence parameters describe the behaviour of a fluorescent molecule in very dilute (~ 10-6 M) solution: the fluorescence spectrum F M ( v ¯ ) ;the fluorescence polarization PM ;the radiative transition probability kFM ; andthe radiationless transition probability kIM .These parameters and their temperature and solvent dependence are those of primary interest to the photophysicist and photochemist. F M ( v ¯ ) and PM can be determined directly, but kFM and kIM can only be found indirectly from measurements of the secondary parameters,the fluorescence lifetime τM , andthe fluorescence quantum efficiency qFM ,where kFM =qFM/τM and kIM =(1-qFM ) τM. The real fluorescence parameters F ( v ¯ ) , τ and ϕF of more concentrated (c > 10-5 M) solutions usually differ from the molecular parameters F M ( v ¯ ) , τM and qFM due to concentration (self) quenching, so that τ > τM and ϕF < qFM. The concentration quenching is due to excimer formation and dissociation (rates kDMc and kMD , respectively) and it is often accompanied by the appearance of an excimer fluorescence spectrum F D ( v ¯ ) in addition to F M ( v ¯ ) , so that F ( v ¯ ) has two components. The excimer fluorescence parameters F D ( v ¯ ) , PD , kFD and kID together with kDM and kMD , and their solvent and temperature dependence, are also of primary scientific interest. The observed (technical) fluorescence parameters F T ( v ¯ ) , τT and ϕ F T in more concentrated solutions usually differ from the real parameters F ( v ¯ ) , τ and ϕF , due to the effects of self-absorption and secondary fluorescence. The technical parameters also depend on the optical geometry and the excitation wavelength. The problems of determining the real parameters from the observed, and the molecular parameters from the real, will be discussed. Methods are available for the accurate determination of F T ( v ¯ ) and τT . The usual method of determining ϕ F T involves comparison with a reference solution R, although a few calorimetric and other absolute determinations have been made. For two solutions excited under identical conditions and observed at normal incidence ϕ F T ϕ F R T = n 2 ∫ F T ( v ¯ ) d v ¯ n R 2 ∫ F R T ( v ¯ ) d v ¯ where n is the solvent refractive index. Two reference solution standards have been proposed, quinine sulphate in N H2SO4 which has no self-absorption, and 9,10-diphenylanthracene in cyclohexane which has no self-quenching. The relative merits of these solutions will be discussed, and possible candidates for an "ideal" fluorescence standard with no self-absorption and no self-quenching will be considered.
