From electromotive-force measurements of the cell without liquid junction: [Formula: see text]through the range 0° to 95° C, calculations have been made of (1) the standard potential of the silver-silver-chloride electrode, (2) the activity coefficient of hydrochloric acid in aqueous solutions from m (molality) =0 to m=0.1 and from 0° to 90° C, (3) the relative partial molal heat content of hydrochloric acid, and (4) the relative partial molal heat capacity of hydrochloric acid. The extrapolations were made by the method of least squares with the aid of punch-card techniques. Data from at least 24 cells were analyzed at each temperature, and 81 cells were studied at 25° C. The value of the standard potential was found to be 0.22234 absolute volt at 25° C, and the standard deviation was 0.02 millivolt at 0° C, 0.01 millivolt at 25° C, and 0.09 millivolt at 95° C. The results from 0° to 60° C are compared with earlier determinations of the standard potential and other quantities derived from the electromotive force.

The National Bureau of Standards (NBS) electric watt in SI units to be: W/sub NBS//W=K/sub W/=1-(16.69+or-1.33) p.p.m. The uncertainty of 1.33 p.p.m. has the significance of a standard deviation and includes the best estimate of random and known or suspected systematic uncertainties. The mean time of the measurement is May 15, 1988. Combined with the measurement of the NBS ohm in SI units: Omega /...

We have constructed a current balance with superconducting field coils for the realization of the SI ampere by comparing mechanical to electrical work. The estimated ultimate accuracy of the realization is 0.1 ppm. We describe and present preliminary results obtained with a room temperature version of the apparatus.

A report of the Faraday constant as determined at NBS via silver coulometry and atomic weight measurements is presented. The uncertainty of the reported result represents a five-fold improvement over measurements made at NBS 20 years ago. The result should contribute to an analysis of the self-consistency of several other fundamental constants measurements. Experimental details have been reported in other publications which are cited in the text.

In 1975, the results of a series of mass measurements undertaken by the National Bureau of Standards were published in Science . The inconsistencies reported seemed to depend on barometric pressure. An inference to be drawn from the report is that buoyant forces on objects weighed in air are somehow incorrectly accounted for by the usual appeal to Archimedes' principle in which the density of air, ρ, is computed from an equation of state. The magnitude of the unexpected effect was estimated as approaching 1 milligram in 1 kilogram over a pressure range from 0.5 to 2.0 atmospheres for objects having a volume difference of 200 cubic centimeters. In a new experiment at the National Bureau of Standards, in which more elaborate and precise equipment was used, the calculation of air density from the atmospheric variables is confirmed to within 0.05 percent, hence within the uncertainty usually claimed for the air density and buoyancy calculations.

Oxygen-free high-purity samples were used in a precise determination of the electrochemical equivalent of silver. A comprehensive mass spectrometric analysis for impurities was performed. Our value agrees well with prior measurements of the same quantity at the National Bureau of Standards (NBS) by Craig and coworkers. We find the electrochemical equivalent of pure silver to be 1.1179648 mg F = 96486.33 ( 24 ) A NBS ⋅ s ⋅ mol - 1 ( 2.5 ppm ) . Attached to this figure is an uncertainty whose random component (standard deviation of the mean of 8 determinations) is 9.5 × 10-7 mg C-1 (0.85 ppm). The root-sum-square of systematic uncertainties of known origin is 1.07 × 10-6 mg C-1 (0.96 ppm). The above value for the electrochemical equivalent of silver leads us to calculate the Faraday to be: F = 96486.33 (24) A NBS · s · mol-1 (2.5 ppm).

A number of weighings of kilogram artifacts have been completed at sites of differing altitude. The artifacts and altitude difference were chosen to amplify the role of the necessary buoyancy corrections and thereby to uncover systematic errors in those corrections as they are usually applied. Small systematic effects were discovered but these are not explainable by buoyancy errors. Rather, we suggest their source is a lack of thermal equilibrium between the artifacts and the balance chamber.

A technique has been devised which is sufficiently accurate to aid in an electrochemical determination of the Faraday constant using the silver coulometer. The technique is used to recover the silver residue which falls from the anode during operation of the silver coulometer. In contrast to previous efforts at recovery, which involved weighing of the silver residue, the method here described is to convert the silver atoms to ions and then to plate the silver onto a cathode held at constant potential with respect to a reference electrode. The current involved in the electrolysis is integrated electronically. An overall standard deviation of 5 μg is achieved for samples ranging in size from 400 μg to 1.8 mg.

This paper describes a simple device which permits mass comparisons in air without appeal to the correction for air buoyancy. The device consists of a canister which is evacuated and weighed on a laboratory balance with a mass inside. A second weighing of another mass in the evacuated canister provides the desired mass comparison. The method was used to determine the mass difference between two stainless steel weights of widely differing densities. With knowledge of this mass difference and of the volume difference one may, by a simple air weighing of the two objects, determine directly the density of the air in the balance case. Densities of air determined by this method were compared with those calculated from the barometric pressure, the temperature, and the relative humidity of the laboratory air. The experimental and calculated values agree throughout to within 1.0 μg cm-3 (where the normal air density is about 1.2 mg cm-3). The calculated and experimental values of day-to-day fluctuations in air density agree to within 0.5 μg cm-3.

There have been many efforts (1, 2, 3, 4, 5) to measure the Faraday by direct electrochemical methods. Of these only the experiments employing the oxidation of iodide (3), the electrode-position of silver (4), and the electrodissolution of silver (5) have ever been viewed seriously as determinations of a fundamental physical constant.

Isopiestic vapor pressure measurements have been made on the ternary system water-sodium chloride-barium chloride at 25 °C. From these data the activity coefficient of each salt in the presence of the other has been calculated. The rule that the logarithm of the activity coefficient of one salt (which is equivalent to its chemical potential) varies linearly with the concentration of the other salt has been investigated. It is shown that this rule is at least approximately valid with the condition usually assumed, namely, that the total ionic strength is kept constant. It is shown, moreover, to be valid for another condition, namely, that the total concentration of ions is kept constant. This latter condition is more suited to isopiestic studies. Finally, the calculation of mutual solubilities from isopiestic data is described.

Isopiestic vapor pressure measurements have been made on the system water-calcium chloride-magnesium chloride at 25°C. Activity coefficients have been evaluated for each salt in the presence of the other in systems of constant total ionic strength. The excess free energy of mixing has been calculated and compared with the values for analogous systems.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOsmotic and Activity Coefficients of Tris(hydroxymethyl) aminomethane and Its Hydrochloride in Aqueous Solution at 25° C.R. A. Robinson and V. E. BowerCite this: J. Chem. Eng. Data 1965, 10, 3, 246–247Publication Date (Print):July 1, 1965Publication History Published online1 May 2002Published inissue 1 July 1965https://pubs.acs.org/doi/10.1021/je60026a013https://doi.org/10.1021/je60026a013research-articleACS PublicationsRequest reuse permissionsArticle Views273Altmetric-Citations12LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

Sep te mber 15, 1964) I sop iestic vapor press ure meas urements h ave been made on t he tern a ry syste m watersodium chloride-barium chloride at 25 °e.From t hese data the activity coe ffi cient o f each salt in t he presence of t he other has been calcul ated.The rul e t hat the logarithm of the ac tivity coefficient of one salt (which is eq uiva lent to its chemica'!pote ntial) va ries linearly with the concentration of t he other salt has been in vestigated.It is s hown t hat th is rule is at least a pproximately vali d w ith the co ndi t ion usually ass um ed, na mely, t hat t he total ionic stre ngth is kept co nstant.It is sh own, moreover, to be valid for another con di t ion, namely, that the total concentration of ions is kept co nstant.This latter co nd it ion is more suited to isopiestic studi es.Finally, t he calculation of mutual solu bil ities f rom isop iestic data is described .

The question is discussed whether, and to what extent, the vapor pressure lowering of an aqueous solution containing two salts A and B can be compounded additively from the vapor pressure lowerings of a solution containing the salt A alone and another solution containing the salt B alone. In some instances the additivity of vapor pressure lowering is true within less than 0.5 percent; six systems have been examined and the greatest deviation from additivity amounts to 2.0 percent.

The thermodynamic properties of the ternary system: water-glycine-potassium chloride at 25 °C have been evaluated by means of isopiestic vapor pressure measurements. The effect of added glycine on the activity coefficient of potassium chloride has been calculated and the effect of added potassium chloride on the activity coefficient of glycine. The variation of the activity coefficient of potassium chloride has been studied previously by Roberts and Kirkwood, using an entirely different method-the measurement of the emf of suitable concentration cells. The agreement between these independent measurements is shown to be excellent within the concentration ranges common to both experiments.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTHE THERMODYNAMICS OF THE TERNARY SYSTEM: UREA-SODIUM CHLORIDE-WATER AT 25°V. E. Bower and R. A. RobinsonCite this: J. Phys. Chem. 1963, 67, 7, 1524–1527Publication Date (Print):July 1, 1963Publication History Published online1 May 2002Published inissue 1 July 1963https://doi.org/10.1021/j100801a030RIGHTS & PERMISSIONSArticle Views344Altmetric-Citations99LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (506 KB) Get e-Alerts

V. E. Bower and R. A. Robinson, Trans. Faraday Soc., 1963, 59, 1717 DOI: 10.1039/TF9635901717

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTISOPIESTIC VAPOR PRESSURE MEASUREMENTS OF THE TERNARY SYSTEM: SORBITOL-SODIUM CHLORIDE-WATER AT 25°V. E. Bower and R. A. RobinsonCite this: J. Phys. Chem. 1963, 67, 7, 1540–1541Publication Date (Print):July 1, 1963Publication History Published online1 May 2002Published inissue 1 July 1963https://pubs.acs.org/doi/10.1021/j100801a033https://doi.org/10.1021/j100801a033research-articleACS PublicationsRequest reuse permissionsArticle Views123Altmetric-Citations39LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts