bluuebunny/crossref_metadata_2025 huggingface dataset:
Bayesian routes and unit roots: De rebus prioribus semper est disputandum
Authors: Phillips P. C. B.
Published: July 2007

This paper provides detailed responses to the following eight discussants of my paper ‘To criticize the critics: an objective Bayesian analysis of stochastic trends’: Gary Koop and Mark Steel; Edward Learner; In‐Moo Kim and G. S. Maddala; Dale J. Poirier; Peter C. Schotman and Herman K. van Dijk; James H. Stock; David DeJong and Charles H. Whiteman; and Christopher Sims. This reply puts new emphasis on the call made in the earlier paper for objective Bayesian analysis in time‐series; it underlines the need for a new approach, especially with regard to posterior odds testing; and it draws attention to a new methodology of Bayesian analysis developed in a recent paper by Phillips and Ploberger (1991a). Some new simulations that shed light on certain comments of the discussants are provided; new empirical evidence is reported with the extended Nelson‐Plosser data supplied by Schotman and van Dijk; and the new Phillips‐Ploberger posterior odds test is given a brief empirical illustration.
The role of the list price in housing markets: Theory and an econometric model
Authors: Horowitz Joel L.
Published: July 2007

Houses are routinely sold at prices below, but rarely sold at prices above, their list prices. List prices appear to be price ceilings that preclude the possibility of sales at higher prices. This paper presents a theory of sellers' behaviour that explains why there are list prices in housing markets and why list prices are distinct from sellers' reservation prices. The theory forms the basis of an econometric model that has been estimated using data from the Baltimore, MD, area. The estimated model predicts sale and reservation prices conditional on list prices. The predictions of sale prices are considerably more accurate than those obtained from a standard hedonic price regression. The estimated model also explains why sellers may not be willing to reduce their list prices even after their houses have remained unsold for long periods of time.
Estimation of data measured with error and subject to linear restrictions
Authors: Weale Martin
Published: July 2007

Variables are often measured subject to error, whether they are collected as part of an experiment or by sample surveys. A consequence of this is that there will be different estimates of the same variable, or, more generally, linear restrictions which the observations should satisfy but fail to. With knowledge of the variances of the various observations, it has been shown elsewhere that maximum‐likelihood estimates of the observations can be produced. This paper shows how, given a sequence of such observations, estimates can be produced without knowledge of data reliabilities. The method is applied to estimates of constant price US GNP. It suggests that 64 per cent of the discrepancy should be attributed to the expenditure estimate, with only 36 per cent going to the income/output estimate. The current method of presentation, on the other hand, places the whole of the error in the income/output estimate.
Some strange properties of panel data estimators
Authors: Robertson D. , Symons J.
Published: July 2007

We study the biases that are likely to arise in practice with panel data when parameters vary across individuals, but this is not allowed for in estimation. We consider both stationary and non‐stationary regressors. We find that biases can be severe for relatively small parameter variation, and that this problem is hard to detect. We study in some detail by Monte‐Carlo the performance of the Anderson‐Hsiao estimator in the presence of this particular mis‐specification.
Survey evidence on the rationality of expectations
Authors: Ivaldi Marc
Published: July 2007

Data on expectations collected by business surveys offer the opportunity to test the rational expectation hypothesis. Tests directly based on qualitative data are not powerful because of the nature of the data. An alternative method is proposed in this paper. We apply the usual orthogonality conditions of rationality to the unobservable variables which are assumed to trigger the categorical responses of surveys when they cross certain thresholds. To implement the test, an original estimation method for latent variable models using indicators is required. The results show that the Hypothesis is not always rejected for the expectations of changes in demand drawn from surveys of French manufacturing industry.
International evidence on persistence in output in the presence of an episodic change
Authors: Raj Baldev
Published: July 2007

This paper uses some newly developed methods and techniques to examine the dynamic properties of international output in the presence of a structural break. We provide statistical evidence to show that the unit root test results can, in some cases, be sensitive to whether a one‐time structural break in the data is modelled exogenously or endogenously. However, in most cases the unit root test results remain robust to specification of the structural break exogenously or endogenously; moreover, we find that the null hypothesis of a unit root in output can be rejected in favour of a ‘flexible’ trend alternative for a number of countries such as Canada, Denmark, France, and the United States.
Polynomial approximations in cross‐sectional models
Authors: Byron R. P.
Published: July 2007

The time‐series distributed lag techniques of econometrics can be usefully applied to cross‐sectional, spatial and cross‐section time‐series situations. The application is perfectly natural in cross‐section, time‐series models when regression coefficients evolve systematically as the cross‐section grouping variable changes. The evolution of such coefficients lends itself to polynomial approximation or more general smoothing restrictions. These ideas are not new, Gersovitz and McKinnon (1978) and Trivedi and Lee (1981) providing two of the earliest applications of cross‐equation smoothing techniques. However, their applications were in the context of coefficient variation due to seasonal changes and this may account for the non‐diffusion of these techniques. The approach here is illustrated in the context of age‐specific household formation equations based on census data, using Almon polynomials when the regression coefficients vary systematically by age group. A second application is provided, using spatial data, explaining the incidence of crime, by region; using polynomial and geometric smoothing to model distance declining regional effects.
Intra‐day futures price volatility: Information effects and variance persistence
Authors: Locke P. R. , Sayers C. L.
Published: July 2007

This paper was prepared for presentation at the Conference on Nonlinear Dynamics and Econometrics, UCLA, 5–6 April, 1991, under the title ‘Information and chronological time effects in intra‐day futures price volatility.’ The authors are grateful to participants of the Nonlinear Dynamics Conference and to Leigh Riddick, George Wang, and two anonymous referees for helpful comments. The BDS program was provided by W. D. Dechert and the BISPEC program was provided by Doug Patterson. The views stated within are those of the authors, and do not necessarily reflect those of the Commodity Futures Trading Commission or its staff.

This paper examines the role of the rate of information arrival proxy variables, as they relate to persistence in the variance structure of minute‐by‐minute S&P 500 Index Futures returns series. The role of contract volume, floor transactions, the number of price changes, executed order imbalance, and an information composite in reducing variance persistence is examined. All proxy variables are found to explain a significant amount of returns variance. While the characteristics of returns data vary daily, some evidence of remaining variance persistence is found, regardless of the definition of the rate of information arrival variable. Our results suggest that utilization of a pure ARCH‐type model for highfrequency returns data implies a mis‐specification.
The cyclical and secular behaviour of the labour input: Comparing efficiency units and hours worked
Authors: Hanse G. D.
Published: July 2007

A monthly labour input series designed to correct for the fact that all hours worked are not of the same quality is constructed and its properties compared with unadjusted hours worked. This efficiency units series is constructed from BLS data on hours worked and earnings by age and sex. The cyclical fluctuations displayed by the efficiency units series are smaller on average than those displayed by hours worked, although the difference is not large. However, the secular behaviour of the series is quite different: hours worked per capita displays a significant positive trend while efficiency units per capita does not.
International real interest rate equalization. A multivariate time‐series approach
Authors: Kugler P. , Neusser K.
Published: July 2007

This paper investigates the dynamic behaviour of monthly ex post real interest rates from several countries over the period 1980 to 1991. It is found that real interest rates are stationary over this period and that deviations from real interest parity are significant in the short run but disappear in the long run. The latter evidence is established using the concept of co‐dependent time series proposed by Gourieroux and Peaucelle (1989) for the analysis of multivariate stationary time series.
Income and wealth inequality and the life cycle. A non‐parametric analysis for China
Authors: Pudney S.
Published: July 2007

This paper uses the techniques of non‐parametric density and regression estimation to estimate the Chinese age/income and age/wealth distributions, using survey data relating to 1987. Although there is evidence of a clear life‐cycle profile of income earning and wealth accumulation, the results suggest that only a small part of observed inequality can be explained by life‐cycle factors. This finding contradicts the results of some other researchers.
Production cost structure of us hospital pharmacies: Time‐series, cross‐sectional bed size evidence
Authors: Okunade A. A.
Published: July 2007

There are current concerns about potential factor substitutions and their implications for factor employments and cost containment in US hospital pharmacies. A translog production cost model is estimated for these pharmacies, using 1981–9 times‐series data consisting of seven cross‐sectional bed size classes per year. Zellner's joint GLS estimation of three‐factor cost share equations and the parent translog cost function reveals that pairwise factor substitutions are severely limited; production is non‐homothetic, occurring in the range of scale diseconomies; biased and pure technical change effects dominate the scale‐augmenting component. Implications of findings are rationalized in the context of the emerging biopharmaceutical technologies.
A count‐amount model with endogenous recording of observations
Authors: Van Praag B. M. S. , Vermeulen E. M.
Published: July 2007

This paper discusses some of the problems which are encountered if an event Ỹ is only recorded if its value satisfies a recording criterion A. It follows that we get an incorrect idea of the frequency of the events and of its true distribution. In order to solve these problems, an econometric model has been constructed by means of which consistent estimation of the true parameters is possible. The model is estimated on consumer purchases, where the number of purchases is assumed to be NEGBIN‐distributed and the purchase amounts obey a lognormal distribution. Purchases are only recorded if their value exceeds Dfl. 10. It is shown that ignoring the recording condition will result in biased estimates and invalid predictions. Apart from this, the model is, among others, relevant for insurance problems, marketing surveys and criminological and epidemiological phenomena.
A simulation estimation analysis of the external debt crises of developing countries
Authors: Hajivassiliou V. A.
Published: July 2007

In this paper we develop models of the incidence and extent of external financing crises of developing countries, which lead to multiperiod multinomial discrete choice and discrete/continuous econometric specifications with flexible correlation structures in the unobservables. We show that estimation of these models based on simulation methods has attractive statistical properties and is computationally tractable. Three such simulation estimation methods are exposited, analysed theoretically, and used in practice: a method of smoothly simulated maximum likelihood (SSML) based on a smooth recursive conditioning simulator (SRC), a method of simulated scores (MSS) based on a Gibbs sampling simulator (GSS), and an MSS estimator based on the SRC simulator. The data set used in this study comprises 93 developing countries observed through the 1970–88 period and contains information on external financing responses that was not available to investigators in the past. Moreover, previous studies of external debt problems had to rely on restrictive correlation structures in the unobservables to overcome otherwise intractable computational difficulties. The findings show that being able for the first time to allow for flexible correlation patterns in the unobservables through estimation by simulation has a substantial impact on the parameter estimates obtained from such models. This suggests that past empirical results in this literature require a substantial re‐evaluation.
Estimates of the demand for medical care under different functional forms
Authors: Hunt‐McCool Janet , Kiker B. F. , Ng Ying Chu
Published: July 2007

We estimate price and income elasticities from a linear, log‐linear, and the almost ideal demand model (with and without an adjustment for selectivity bias) in an effort to show that special attention should be paid to the underlying assumptions of consumer behaviour when estimating a medical care demand model. The literature on medical care utilization is extended by incorporating two major components of spending as separate demands in a system of medical care spending. We find that estimates of elasticities vary depending on the functional form of the estimating equation, thus questioning the usefulness for policy purposes of single estimates of elasticities.
A structural model of aircraft engine maintenance
Authors: Kennet D. Mark
Published: July 2007

We develop and estimate a simple regenerative optimal stopping model of aircraft engine maintenance that attempts to describe the behaviour of airline maintenance personnel. The model assumes that the decision to send an engine to the shop for overhaul is the solution to a stochastic dynamic programming problem that trades off the expected cost of continuing operation with the attendant risk of engine failure with the cost of performing the overhaul. We estimate the model using 42 engine histories from Pratt & Whitney, Inc. Estimation results indicate that such a model does not explain observed engine histories before deregulation, but does fit the data in the era since deregulation. The model also provides insight into the perceived relative costs of engine maintenance, in‐flight shutdown, and ordinary operation.
Unemployment dynamics and labour market tightness: An empirical evaluation of matching function models
Authors: Storer P.
Published: July 2007

The implications of matching function models for the relationship between labour market tightness and the transition probability into employment are summarized. These implications are then tested using monthly data for three Canadian provinces: British Columbia, Ontario, and Quebec. Testing methods use flexible regression techniques so as to reduce the effect of any extraneous restrictions. The results show rough concordance between theoretical assumptions and empirical facts. Evidence of non‐linearity in the estimated relationships favours a search‐theoretic model of labour markets over one based on queues and some quantitative results offer guidance to those using ‘calibrated’ search models in theoretical analysis.
Labour‐use efficiency in Swedish social insurance offices
Authors: Kumbhakar Subal C. , Hjalmarsson Lennart
Published: July 2007

This paper considers the estimation of frontier production functions in panel data models. It proposes a multi‐stage method to obtain estimates of (1) the parameters of a flexible input requirement function and (2) technical inefficiency decomposed into time‐invariant (firm‐specific), time‐varying, and the residual components. The proposed method is used to analyse labour‐use efficiency of Swedish local social insurance offices on the basis of a large panel of observations during the time period 1974–84. Empirical results show: (1) substantial variations in labour‐use efficiency among these offices, with the mean efficiencies declining over time; (2) presence of economies of scale, thereby meaning that most of the offices were of suboptimal size.
Convergence in international output
Authors: Bernard Andrew B. , Durlauf Steven N.
Published: July 2007

This paper proposes and tests new definitions of convergence and common trends for per capita output. We define convergence for a group of countries to mean that each country has identical long‐run trends, either stochastic or deterministic, while common trends allow for proportionality of the stochastic elements. These definitions lead naturally to the use of cointegration techniques in testing. Using century‐long time series for 15 OECD economies, we reject convergence but find substantial evidence for common trends. Smaller samples of European countries also reject convergence but are driven by a lower number of common stochastic trends.
A nonlinear approach to US GNP
Authors: Potter Simon M.
Published: July 2007

A univariate nonlinear model is estimated for US GNP that on many criteria outperforms standard linear models. The estimated model is of the threshold autoregressive type and contains evidence of asymmetric effects of shocks over the business cycle. In particular the nonlinear model suggests that the post‐1945 US economy is significantly more stable than the pre‐1945 US economy.
Testing for homogeneity in demand systems when the regressors are nonstationary
Authors: Ng Serena
Published: July 2007

An implication of optimizing theory is that demand functions are homogeneous of degree zero in prices and nominal income. Evidence based on estimations of demand systems has repeatedly found this restriction to be rejected by the data. However, the hypothesis is often formulated in terms of regressors that are non‐stationary. This paper re‐examines the evidence for homogeneity in light of recent developments in time‐series econometrics with special emphasis on the treatment of trends. We find the demand system to be stochastically but not deterministically cointegrated. Using techniques developed for estimating cointegrating vectors in the presence of deterministic trends, we re‐estimate the demand system and find that homogeneity holds in many cases.
Maximum likelihood estimation of a GARCH‐stable model
Authors: Liu Shi‐Miin , Brorsen B. Wade
Published: July 2007

Maximum likelihood is used to estimate a generalized autoregressive conditional heteroskedastic (GARCH) process where the residuals have a conditional stable distribution (GARCH‐stable). The scale parameter is modelled such that a GARCH process with normally distributed residuals is a special case. The usual methods of estimating the parameters of the stable distribution assume constant scale and will underestimate the characteristic exponent when the scale parameter follows a GARCH process. The parameters of the GARCH‐stable model are estimated with daily foreign currency returns. Estimates of characteristic exponents are higher with the GARCH‐stable than when independence is assumed. Monte Carlo hypothesis testing procedures, however, reject our GARCH‐stable model at the 1% significance level in four out of five cases.
Heterogeneity biases, distributional effects, and aggregate consumption: An empirical analysis using stratified microdata
Authors: Fortin Nicole M.
Published: July 2007

Using stratified microdata from the Canadian FAMEX (78–86) surveys, this paper investigates whether observed heterogeneity in marginal propensities to consume across strata actually hinders the aggregation process. Despite significant heterogeneity in marginal responses, the divergences between aggregate predicted consumption and the predictions from a model that uses average strata responses are found to be small, whenever the strata demands are approximatively linear at the mean and the commodity group considered is not a luxury good. On the other hand, some cross‐sectional estimates obtained by pooling the strata are shown to be contaminated by unwanted cross‐moments. Further, the analysis reconciles the fact that while there exists significant heterogeneity in consumer demands, the related distributional effects in the aggregate equation have not been found to be important.
The rapid determination of tar and bitumen in road materials
Authors: Green E. H. , Cox E. A.
Published: July 2007

A method is described for the determination of the binder content of bituminous mixtures, rapid enough for plant control and sufficiently accurate for routine analysis. The soluble binder is extracted from the mixture with methylene chloride; from an aliquot portion of the solution the solvent is removed by distillation under reduced pressure, and the binder weighed. The time required for the estimation of binder content varies from 30 to 90 minutes, according to the type of mix. Analysis of over one hundred representative bituminous road materials has shown excellent agreement with figures obtained by British standard methods. A brief review of standard methods is given with the times required for analysis.
The photogelation of rubber sols in the absence of accelerators
Authors: Buckingham R. , Planer G. V.
Published: July 2007

On irradiation of rubber sols with ultra‐violet light in the absence of oxygen, gelation takes place under certain conditions. The nature of thin reaction was studied by following its progress by means of viscosity measurements. Reaction curved determined for rubber sols in carbon tetrachloride, in the absence of accelerators, were found to be fundamentally, of the same type as those obtained in their presence. They differed, however, in showing a slight initial decrease in viscosity owing 10 degradation, probably due to traces of oxygen. The mechanism of the reaction and the possible structures of the reaction feature are discussed.
Colorimetric determination of less than 0·001% S as thiophen in pure benzoles
Authors: French K. H. V.
Published: July 2007

The use of pure benzole as a raw material for the manafacture of plastics has demanded the production of a grade containing very low quantities of sulphur as thiophen. Recent experience has shown that, in order to estimate this thiophen, which may be present in quantities of the order of 0·001% wt. sulphur as thiophen, reliance has been placed almost entirely on the well‐known isatin test, although many variations of the test are being used and comparable results are not being obtained. The present work was undertaken to enable a reliable test to be suggested that is capable of standardisation in the manner of other tests commonly used for testing tar and its products.
A study of the action of borax in retarding the setting of plaster of Paris
Authors: Buchanan A. S. , Worner K.
Published: July 2007

It is a matter of common knowledge that borax (Na2B4O7) is a very efficient agent for retarding the set of plaster of Paris. Its effect on the setting time is shown by the typical curve given in Fig. 1 (after Gibson and John‐on1). One of the explanations offered2 for this retardation phenomenon is that borax is physically adsorbed on the surface of the crystal, thus reducing the rates of solution of the hemihydrate and the formation of gypsum nuclei. Thin short investigation was initialed to test and the validity of this postulation.
A rapid method for the determination of the specific surface and mean particle size of black powders
Authors: Frith F. , Mott R. A.
Published: July 2007

The tinting strength test has been standardised so as to obtain complete dispersion of carbon blacks down to a size of 50 mμ (= 0·000030 mm.) or less. Standardisation of the test has been possible with carbon blacks whoso size (within the range 300 to 30 mμ) has been determined by the electron microscope. A discussion of the relationship between surface area and mean particle size for particles which are spherical, cubical, or oven slightly prismatic, shows that the method can be used to assess moan specific surface or mean particle size for black powders below 50mμ (0·050 ram. or 240 B.S. mesh), that is for sub‐sieve sizes. The range of sizes which can be assessed extends to lower limits of size than can be examined by sedimentation tests or microscopical counts. The method has been applied particularly in a study of the fine grinding of coke and coal, and could be applied to other black powders. Its application to white powders should be possible if suitable standards can be chosen from measurements by the electron microscope. The method is simple, requires little equipment and is rapid to carry out when the art has been acquired.
A simple photo‐electric absorptiometer
Authors: Clayson H. R. , Scott B. A.
Published: July 2007

This paper describes the construction and operation of a straightforward photo‐electric absorptiometer of original design. The instrument may be readily constructed in the laboratory workshop from standard parts, and is suitable for most routine colorimetric determinations at present carried out with more complicated and expensive apparatus. Tests in these laboratories have shown that the instrument is sufficiently robust and stable to withstand continued use under routine conditions and that the accuracy of reading and stability of calibration are both well up to the standard set by more expensive instruments. The preliminary design was drawn up on the following broad principles, which were considered to be the characteristics of an ideal ubsorptiometer : (1) Robust and simple construction. (2) Freedom from personal errors. (3) Good reproducibility of readings. (4) Permanency of calibration, (5) Rapid reading. (6) Liquid cell easy to, fill and drain, preferably without removal from the instrument.
Polymerisation of allyl esters
Authors: Simpson W.
Published: July 2007

The benzoyl peroxide catalysed polymerisation of diallyl phthalate is shown to proceed by a zero order reaction in the early stages to give a linear or lightly branched unsaturated polymer (β‐polymer). At approximately 25% conversion, gel formation occurs duo to the formation of a three‐dimensional polymer (γ‐polymer). Thereafter the β‐polymer concentration falls rapidly as the γ‐polymer content increases.

The polymerisation of mixtures of unsaturated polyesters, typified by diethylene maleste, and diallyl phthalate is shown to result mainly in a three‐dimensional copolymer.

The effect of temperature variation on multi‐functional polymerisation reactions of the above type is discussed. It is suggested that, as the polymerisation temperature is increased, fewer cross‐links by primary valence bonds are formed, i.e., Houwink's “Lockerstellen” theory may be extended to include polymers of this type.
A note on the effect of tinplate and of lacquered surfaces on the oxidative deterioration of butterfat
Authors: Lea C. H.
Published: July 2007

Little difference was observed in the storage life of butterfat when packed in sealed tinplate and in lacquered containers. Dispersed as very thin films of the order of 0·02‐0·06 nun. in thickness, butterfat was considerably less stable on a tinplate surface than on lacquered blackplate, on “fruit” or “meat” lacquered tinplate or on glass. These observations are discussed in connection with parallel experiments on spray dried full cream milk powder, for which, on a number of occasions, better keeping properties have been observed in lacquered than in plain tinplate containers, particularly at high storage temperatures.
A procedure for the characterisation of the acetic acid bacteria. Part II
Authors: Tošić Jezdimir , Walker Thomas Kennedy
Published: July 2007

A record is given of the experimental data which were obtained when ten authentic cultures of named species of Acctobacter (from the National Collection of Type Cultures, The Lister Institute, Elstree, Herts.) were examined by the standardised technique, described in Part I. The observations permit comparison under identical conditions of the respective types of growth of these organisms; they permit also direct comparison of other features which the organisms exhibit, and which prove useful for diagnostic purposes. Hitherto, such a systematic comparison of the Acelobacter species has not been published. The information thus obtained should be helpful in the task of differentiating between species and, considered in conjunction with further physiological and biochemical data which may be obtained by more detailed tests, it provides evidence sufficient for identification.
Transactions and communications the production of lubricating oils from the olefines produced in the fischer‐tropsch synthesis
Authors: Gall D.
Published: July 2007

The preparation of lubricating oils by the AlCl2 polymerisation of the olefines present in the primary product obtained by atmospheric pressure synthesis from carbon monoxide and hydrogen (ratio 1 :2) over a cobalt catalyst has been carried out in 2‐gallon batches. The effect of varying temperature, catalyst and boiling range of starting material on the reaction and its products is described. The oils obtained possess properties which approximate to the requirements of the Air Ministry Specification D.T.D. 109 for aircraft lubricants in all respects except the increase in viscosity on oxidation. It was found possible to overcome this disability subjecting the oils to a carefully controlled hydrogenation in the presence of molybdenum disulphide.
Improved methods for the preparation of the X‐ray contrast media iodoxyl and diodone
Authors: Hackman R. H. , Lemberg R.
Published: July 2007

Methods for the preparation of Iodoxyl and Diodone, X‐ray contrast substances for the visualisation of the urinary tract, are given. Improved methods of iodination and methylation are described.
The effect of cooking on the creatine‐creatinine, phosphorus, nitrogen and pH values of raw lean beef
Authors: Bendall J. R.
Published: July 2007

This survey of the changes in the analytical values of meat during cooking was undertaken in order to contribute towards an explanation of the changes in nutritive value, flavour, texture and appearance. A knowledge of these accurately determinable quantities is an essential preliminary to a study, which is contemplated, of the subjective characters enumerated. Some, interesting points of fundamental importance emerge: the nature of the soluble phosphorus compounds in meat, reflecting the degradation of the more complex molecules present in living tissue: the case of hydrolysis of the proteins by acid in the cold, but their relative stability to boiling for 1 hour in aqueous solution; the partial breakdown of the proteins on pressure‐cooking to give amino.acids and peptides; the destruction of creatino or creatinine at 120°c.; and the interesting relation, ships between concentration of protein and change in pH due to coagulation by heat.
Analytical reactions with organic reagents
Authors: Steigmann A.
Published: July 2007

New specific or very selective organic reagents are described: acid solutions of thionine for thiosulphates; acid solutions of α‐diketones for ureas, guanidines and nitrates, and mineral acid solutions of resorcinol for nitroso compounds. The resorcinol sugar reaction being interfered with by nitrates and nitrites, attention is drawn to hydrochloric acid solutions of urea and tryptophane for the detection of carbohydrates. New reactions of anionic and cationic wetting agents for earth alkalis and metal acids (e.g. of molybdenum and tungsten) respectively show again the analytical value of soaps and wetting agents. Instead of wetting agents special preparations of anionic and cationic “gelatines” may be of value. ϵ‐Bensylthiuronium chloride in hot ammoniacal solutions, i. e. benzyl mercaptan, was found to be a sensitive and very selective cobalt and nickel reagent.
The effect of sieve loading on the results of sieve analysis of natural sands
Authors: Shergold F. A.
Published: July 2007

An experimental investigation has been made into the effects of a number of factors on the results of stove analysis of natural sands. The factors studied included samples size, particle size distribution in the sample and the duration of sieving. Microscopic examination showed that the particle shape was similar in all the materials tested regardless of size. The work showed that overloading of the sieves leads to inaccurate results, and that reduction of sample size is a more effective remedy for overloading than prolongation of sieving time. Values are given for the maximum desirable loading for a number of sieves, and recommendations are made for the adoption of a standard weight of sample for sieve analysis of natural sands. The most recent British Standard method for Sieve Analysis (B.S. 882:1944, Appendix B) has been based on this work.
The analysis of external deposits from boilers part I. General remarks on the nature of boiler deposits and their examination
Authors: Crossley H. E. , Edwards A. H.
Published: July 2007

A description is given of the nature of external boiler deposits and of the methods used for examination. Special considerations attach to the collection of deposits from boilers if a maximum of information regarding their formation is to be obtained. The analytical difficulties arising from the presence of such radicals and elements as sulphate, phosphate, arsenic and boron (which may interfere with the normal procedure) are discussed, and methods for avoiding these difficulties are suggested. A rapid method is given for the determination, us mixed sulphates, of sodium and potassium in the water soluble fraction of a deposit.
The analysis of external deposits from boilers. part II. Method in use at british coal utilisation research association for the analysis of external boiler deposits rich in phosphates
Authors: Edwards A. H.
Published: July 2007

The methods in use at B.C.U.R.A. for the analysis of external boiler deposits rich in phosphates are described. A special procedure is recommended where the phosphate concentration (as P2O2) exceeds 6%, sulphates also being present. It is recommended that a known excess of ferric sulphate be added for the removal of phosphate to the solution prepared for the precipitation of mixed oxides. Methods for the determination of phosphate, sulphate and alkalis are also included.
Comparison of optical and electron microscopy of pigments
Authors: Tilleard O. L. , Smith N. D. P.
Published: July 2007

This paper describes a technique for preparing dispersions of pigment particles suitable for electron microscope examination, and gives illustrations of the extent of the information, as to the shape and size of pigment particles, to be gained from the extremely high resolving power of the electron microscope. Some of the precautions to be taken in interpreting the micrographs are stressed.
Some preliminary investigations of the phenolformaldehyde reaction
Authors: Jones T. T.
Published: July 2007

The reaction between phenol and formaldehyde, takes place us a series of step‐wise reactions which are catalysed by both acids and bases and which proceed under neutral conditions at sufficiently high temperatures. Two types of reaction take place, namely the reaction of formaldehyde with phenol or a phenolic molecule, to form phenolic alcohols containing reacting methylol groups, and the subsequent condensation of these phenolic alcohols with phenol or a phenolic molecule to form larger molecules with elimination of water. Two studies of the initial portion of the reaction between phenol and formaldehyde in aqueous media are described, namely the Kinetics and the Thermochemistry.

Kinetic studies show that a linear relationship exists between antilog (—pH) and the initial rate at which the formaldehyde reacts using HCl as catalyst between pH values of 1·3 and 3 at 100° and 80°. Catalysis by different acids at the same pH value gives rise to similar rates of reaction especially when pH and rate of reaction are measured at the same temperature. This points to catalysis by the hydrogen ion. The second order rate law is best obeyed by all the curves relating to formaldehyde reacted and time at various pH values, at 100° and 80° using HCl as catalyst. A decrease in temperature to 30° causes the rate law to approach first order. A theoretical enquiry shows that a decrease in order of reaction could be explained by the formation of dialcohols, which formation of dialcohols seems more probable at low temperature. In alkaline media, dialcohols also seem to be produced more readily, us indicated by the fact that a first order rate law is obeyed until about 45% of the formaldehyde has reacted.

Thermochemical studies show that the heat evolved during the phenolformaldehyde reaction may also be regarded as derived from the reaction of formaldehyde with a phenolic molecule, and the subsequent elimination of water by condensation. The heats evolved per mole of formaldehyde reacted and water evolved are 4·1 and 16·9 kilocalories respectively. These values are confirmed by combining heats of combustion and heats of mixing data.
The identification and estimation of the montmorillonite group of minerals, with special reference to soil clays
Authors: MacEwan Douglas M. C.
Published: July 2007

A method is described for the detection and estimation of the montmorillonite group minerals by X‐rays, which completely eliminates difficulties due to the change of basal spacing with hydration, allowing a vacuum camera to be used if desired. The method is based on the formation of a montmorillonite‐glycerol complex. It may be combined with either the powder or the oriented aggregate techniques. With the former, and with a vacuum camera, 1% montmorillonite has been detected with ease. A table of data of the main basal reflections of the glycerol‐montmorillonite, in their relation to the basal reflections of other minerals likely to occur in clays, is given. The extension of the method to rough quantitative analysis of montmorillonite clays is described. A discussion is given of the question of distinguishing between montmorillunite and hydrous micas.
Examination of pigments and extenders with the electron microscope
Authors: Tilleard D. L. , Smith N. D. P.
Published: July 2007

This paper discusses the results of electron microscope examination of a number of pigments commonly used in paints, lacquers etc. A table summarises the information available as to particle size and shape as obtained from electron microscopy, optical microscopy and adsorption experiments.
British penicillin production
Authors: Smith E. Lester
Published: July 2007

Several pilot and production units for penicillin were erected in Britain during the war, mostly employing milk bottles or special flasks. The successive operations, washing, filling, autoclaving, inoculating, incubating and harvesting were usually mechanised. Surface culture methods could not compete with submerged culture processes developed in U.S. and now installed in two large British factories, since a single tank may be equivalent to half a million milk bottles. The penicillin is concentrated and purified by adsorption or partition processes and the final penicillin solution is freeze‐dried to increase its stability.
The shape of particles in finely ground powders
Authors: Steinherz A. R.
Published: July 2007

The usual particle size analysis gives data on particle size distribution by weight or by values of a function related to it, e.g., the surface area of particles of the same weight. There are three methods for the determination of particle size in the sub‐sieve range

Measuring the settling velocity, assuming Stokes' law.

Counting particles of the same weight.

Measuring the size of the observed or projected images of the particles in their most stable positions. The results gained by two of these methods have been compared, e.g., by Andreasen,2 by Bishop4 and by Jones,14 but it seems that hitherto no attempt has been made to compare systematically the results of all three, methods. This comparison, originally used merely for verifying purposes, has led to a method of measuring the mean particle shape. This measurement is executed in the following way: a fraction of hearly equal‐sized particles is isolated, their mean volume determined by the counting of particles of the same weight and the mean of their greatest cross sections (i.e., of the images of the particles in their most stable positions) is measured. The mean thickness is then calculated as a quotient of the mean volume and mean cross section, a prismoidal form of the particles being assumed.
The bromide content of underground waters. Part II. Observations on the chlorination of water containing free ammonia and naturally occurring bromide
Authors: Houghton G. U.
Published: July 2007

In Part I of this paper reference was made to the occurrence of up to 2·20 p.p.m. of bromine, combined as bromide, in some underground water supplies of Southern England. The effect of traces of bromide in tests for free chlorine is now discussed. Bacteriological experiments also indicate that when waters containing free ammonia are being chlorinated, the presence of small amounts of bromide leads to a considerable acceleration of the rate of sterilisation: it appears that this effect is marked with 1 p.p.m. of combined bromine but as little as 0·25 p.p.m. may be significant under some conditions. The experiments were mainly confined to the case where the organic content of the water was very small, but this frequently applies in underground supplies.
Electro‐tinplate. Part III. The influence of pickling conditions on the porosity and corrosion resistance of electro‐tinplate
Authors: Caulfield K. W. , Kerr R. , Angles R. M.
Published: July 2007

The quality of electro‐tinned coatings (8 02. per basis bos) from the alkaline and acid baths, on steel, has been determined by means of the thiocyanate test, humidity chamber test and visual appearance after the following pre‐plating treatments : pickling in various acid baths, anodic etching in sulphuric acid, and anodic p.ickling in inhibited sulphuric acid. Coatings of equal1 high quallty can be deposited from cithcr bath, but the deposit {om the alkaline bath is less sensitive to pickling procedure than IS that from the acld bath. The best prc‐treatment for alkaline bath deposits is pickling in inhibited sulphuric acid, and for acid bath deposits 1s anodic etching in sulphuric acid. Pickling in hydrochloric acld cads to coatings of slightly lower quality, but is equally effective with alkaline and acid bath dcposits'and there is no deterioration on prolonging the pickling time up to 5 minutes.
The effect of vapour composition on the assessment of fractionating columns in terms of heights of a transfer unit. Part II
Authors: Storrow J. Anderson
Published: July 2007

Temperature surveys across the diameter of a wetted‐wall fractionating column operating on ethanol‐water mixtures have indicated the form of vapour composition distribution across the column; the assumption being made that the temperatures measured were the condensation temperatures of the vapour. The results illustrate the similarity between the processes of fractionation, uni‐directional diffusion and heat transfer. In fractionation, H.T.U. obtained by thermocouple “sampling”17, 18, and based on the mean vapour compositions are in close agreement with corresponding data obtained by sample‐withdrawal methods.
The use of metallic pigments in the preparation of protective paints
Authors: Mayne J. E. O.
Published: July 2007

An examination of the more available metallic pigments has been made with the object of preparing paints capable of protecting steel cathodically; for this to occur two conditions must be fulfilled:

The metallic pigment must be of a metal less noble than iron.

The pigment particles must be in metallic contact with each other and with the coated steel. It has been shown that whereas aluminium powder, zinc dust, and magnesium powder satisfy condition (i), only zinc dust fulfils condition (ii).
The analysis of anhydrous hydrogen fluoride
Authors: Cook C. D. , Findlater F. G.
Published: July 2007

A procedure is described for the analysis of anhydrous hydrogen fluoride containing) the following impurities: sulphur dioxide, hydrogen sulphide, sulphuric acid, fluorosilic acid and water. The use of glacial acetic acid as a diluent for the anhydrous acid simplifies both the technique and the apparafus previously required when water was used as the diluent.
The esters of 4‐hydroxybenzoic acid and related compounds. Part II. Relationships between the fungistatic activity, and physical and chemical properties of the esters
Authors: Cavill G. W. K. , Vincent J. M.
Published: July 2007

The preparation of the methyl, ethyl, n‐propyl, iso‐propyl, n‐butyl, sec.‐butyl, iso‐butyl, n‐amyl, iso‐amyl, n‐hexyl, (2‐methyl)‐amyl, n‐heptyl and (2‐ethyl)‐hexyl esters of 4‐hydroxybenzoic acid is described.

Results are reported for the toxic action of these esters tested against three moulds: Aspergillus niger, Byssochlamys fulva and Penicillium roqueforti. The inhibitory action is described principally in terms of b (slope of the log. dosage/log. response curve) and an inhibitory index (I), being the reciprocal of the millimolar concentration required to attain a suitable level of inhibition.

Where its determination has been possible (A. niger and B. fulva), b can be regarded as substantially the same for all the esters tested. The logarithm of I plotted against chain length showed a general increase from methyl to hexyl with much less, or no, increase from hexyl to heptyl. The three organisms showed, however, specific differences in their detailed reaction to successive esters. Branched esters, tested against A. niger, were close too, and usually slightly less than, the values for the corresponding normal esters. Differences are reported for the reaction of A. niger to the free acid. Experience with other compounds, particularly as constitution affects b is briefly noted.

Some physico‐chemical aspects of inhibition by the above compounds are discussed.
Cationic exchange reactions of cellulose and their effect on insulation resistance
Authors: Church H. F.
Published: July 2007

It is shown that a wide range of cations can enter into exchange reactions with cellulose and that, when the reaction with given cations is complete, equal numbers of atoms are attached to the cellulose irrespective of valency. Probable mechanisms are discussed. The electrical resistivity of cellulose in the form of insulating paper has also been studied when the material is modified in various ways by cationic exchange. It is shown that the best values of resistivity arc obtained when the cations attached to the cellulose are bivalent and the worst when the exchange is by univalent ions. Of the univalent ions investigated, hydrogen causes the lowest resistivity. The implications of this arc discussed and means of improving insulation resistance are proposed. The effects of cationic exchange on resistivity may readily be masked in commercial insulating papers by electrolytes deposited in the fibres. These must be removed by adequate washing if the full advantage of beneficial cationic exchange is to be achieved.