Journal of research of the National Bureau of Standards. Section A, Physics and chemistry最新文献

Solubility of Ca5(PO4)3OH in the System Ca(OH)2-H3PO4-H2O at 5, 15, 25, and 37 °C Ca5(PO4)3OH在体系Ca(OH)2-H3PO4-H2O中5、15、25和37℃的溶解度

Journal of research of the National Bureau of Standards. Section A, Physics and chemistry Pub Date : 1977-04-01 DOI: 10.6028/jres.081A.017

H. McDowell, T. M. Gregory, W. E. Brown

{"title":"Solubility of Ca5(PO4)3OH in the System Ca(OH)2-H3PO4-H2O at 5, 15, 25, and 37 °C","authors":"H. McDowell, T. M. Gregory, W. E. Brown","doi":"10.6028/jres.081A.017","DOIUrl":"https://doi.org/10.6028/jres.081A.017","url":null,"abstract":"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.","PeriodicalId":94340,"journal":{"name":"Journal of research of the National Bureau of Standards. Section A, Physics and chemistry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1977-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87911570","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 65

Thermophysical Measurements on 90Ti-6AI-4V Alloy Above 1450 K Using a Transient (Subsecond) Technique 1450k以上90Ti-6AI-4V合金的瞬态(亚秒)热物理测量

Journal of research of the National Bureau of Standards. Section A, Physics and chemistry Pub Date : 1977-04-01 DOI: 10.6028/jres.081A.014

A. Cezairliyan, J. McClure, R. Taylor

引用次数: 26

Evaporation of a Liquid Droplet 液滴的蒸发

Journal of research of the National Bureau of Standards. Section A, Physics and chemistry Pub Date : 1977-03-01 DOI: 10.6028/jres.081A.015

R. Kayser, H. Bennett

引用次数: 4

Isotope Effects in the Association Reactions of Methyl and Ethyl Iodide Cations 甲基和乙基碘离子缔合反应中的同位素效应

Journal of research of the National Bureau of Standards. Section A, Physics and chemistry Pub Date : 1977-03-01 DOI: 10.6028/jres.081A.016

L. W. Sieck

引用次数: 1

Diffusion with Discontinuous Swelling 伴有不连续肿胀的扩散

Journal of research of the National Bureau of Standards. Section A, Physics and chemistry Pub Date : 1977-03-01 DOI: 10.6028/jres.081A.013

A. Peterlin

{"title":"Diffusion with Discontinuous Swelling","authors":"A. Peterlin","doi":"10.6028/jres.081A.013","DOIUrl":"https://doi.org/10.6028/jres.081A.013","url":null,"abstract":"Very often a non-solvent diffuses into a glassy polymer with a steep concentration profile proceeding at an almost constant rate v yielding a weight gain proportional to time. Such a diffusion is called type II diffusion in order to distinguish it from the more usual “Fickian” diffusion proceeding without such a constant concentration front and yielding, at least in the beginning, a weight gain proportional to the square root of time. It turns out that the conventional diffusion equation without any special new term but with a diffusion coefficient rapidly increasing with concentration has a series of solutions representing exactly such type II diffusion with v as a completely free parameter which determines the steepness of concentration front. With the usual boundary conditions and infinite medium the diffusion coefficient has to become infinite at the highest penetrant concentration. This case can be considered as an extreme limit which is approached to a high degree in an actual experiment. The finite sample thickness, however, requires only a very large but not an infinite diffusion coefficient. Hence type II diffusion is only a special case of possible diffusion processes compatible with the conventional diffusion equation without any need for new terms if only the diffusion coefficient increases sufficiently fast with penetrant concentration.","PeriodicalId":94340,"journal":{"name":"Journal of research of the National Bureau of Standards. Section A, Physics and chemistry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1977-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91052846","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 33

Thermodynamics of the Densification Process for Polymer Glasses 聚合物玻璃致密化过程的热力学

Journal of research of the National Bureau of Standards. Section A, Physics and chemistry Pub Date : 1977-03-01 DOI: 10.6028/jres.081A.018

J. McKinney, R. Simha

引用次数: 36

The NBS Two-Pressure Humidity Generator, Mark 2 NBS双压湿度发生器，Mark 2

Journal of research of the National Bureau of Standards. Section A, Physics and chemistry Pub Date : 1977-02-01 DOI: 10.6028/jres.081A.010

S. Hasegawa, J. W. Little

引用次数: 51

Frequency Dependence of Intrinsic Stress and Birefringence Tensor of Bead/Spring Model of Polymer Solutions 聚合物溶液珠/弹簧模型的固有应力与双折射张量的频率依赖性

Journal of research of the National Bureau of Standards. Section A, Physics and chemistry Pub Date : 1977-02-01 DOI: 10.6028/jres.081A.012

A. Peterlin, J. Fong

{"title":"Frequency Dependence of Intrinsic Stress and Birefringence Tensor of Bead/Spring Model of Polymer Solutions","authors":"A. Peterlin, J. Fong","doi":"10.6028/jres.081A.012","DOIUrl":"https://doi.org/10.6028/jres.081A.012","url":null,"abstract":"The recently obtained complete solution of the simultaneous diagonalization of matrices H A and H in the hydrodynamic diffusion equation has basically changed the diagonal values vp of the symmetric matrix H of hydrodynamic interaction between all the beads of the elastic random coil model of the isolated macromolecule in solution. Since these values enter explicitly the expressions for the intrinsic stress and refractive index tensor in an alternating flow field if based on the concept of internal viscosity of the model one had to recalculate all values obtained formerly by using the then generally accepted erroneous set of vp data. The new vp equal unity independent of p while the old values were larger than 1 for small p and smaller for large p. Hence their too large contributions in the former range are partially compensated by their too small contributions in the latter region. As a consequence in the whole range investigated, between 3 and 300 chain links, the differences in rheological and rheooptical effects are relatively small, up to a factor of 2, although at higher link number the differences tend to grow with the logarithm of this number.","PeriodicalId":94340,"journal":{"name":"Journal of research of the National Bureau of Standards. Section A, Physics and chemistry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1977-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83025519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Atlas of the I2 Spectrum from 19 000 to 18 000 cm−1 19 000 ~ 18 000 cm的I2光谱图集−1

Journal of research of the National Bureau of Standards. Section A, Physics and chemistry Pub Date : 1977-02-01 DOI: 10.6028/JRES.081A.006

J. D. Simmons, J. T. Hougen

引用次数: 45

On the Atomic Weight of Gallium 论镓的原子量

Journal of research of the National Bureau of Standards. Section A, Physics and chemistry Pub Date : 1977-02-01 DOI: 10.6028/jres.081A.002

G. Marinenko

引用次数: 18