X-ray determination of crystallinity and orientation in poly(ethylene terephthalate)

The measurement of crystallinity and orientation in poly(ethylene terephthalate) is discussed. A simple procedure is given for the estimation of orientation from the (1 05) plane, and it is shown that methods which use the equatorial planes are subject to certain disadvantages. In addition a method is given for the measurement of x-ray crystallinity. The technique is applied to fibers and films of various treatments and a linear relation is found between density and x-ray crystallinity.     

Ion-chromatography of metals with post-column ion displacement

A post-column reagent mixture of Eriochrome Black T and magnesium-EDTA complex is added to the eluent from an ion-chromatograph. Eluted metal cations displace the magnesium, which then forms a complex with the Eriochrome Black T. The absorbance of this complex is measured at 520 nm. Detection limits for several cations are in the mug/ml range.     

Optimisation of sinking funds for major repairs in a housing association

Changes to the financial framework regulating housing associations require them to create a sinking fund that will accrue the necessary cash for future maintenance work to their stock. This paper presents an alternative to the conventional methods by using a Linear Programming model to obtain sinking fund strategies. The relevance of such modelling is discussed with reference to the evolving Sinking Fund system in the UK and European Housing Association movements. The methodology is applied to data from a Housing Association in Scotland. The paper concludes that the LP model offers a degree of flexibility not found in existing practice. The work has relevance to the long-term maintenance management of any built asset.     

The unusual importance of activity coefficients for micelle solutions illustrated by an osmometry study of aqueous sodium decanoate and aqueous sodium decanoate + sodium chloride solutions

Freezing-point and vapor-pressure osmometry data are reported for aqueous sodium decanoate (NaD) solutions and aqueous NaD + NaCl solutions. The derived osmotic coefficients are analyzed with a mass-action model based on the micelle formation reaction qNa(+) + nD(-) = (Na(q)D(n))(q-n) and Guggenheim equations for the micelle and ionic activity coefficients. Stoichiometric activity coefficients of the NaD and NaCl components and the equilibrium constant for micelle formation are evaluated. Illustrating the remarkable but not widely appreciated nonideal behavior of ionic surfactant solutions, the micelle activity coefficient drops to astonishingly low values, below 10(-7) (relative to unity for ideal solutions). The activity coefficients of the Na(+) and D(-) ions, raised to large powers of q and n, reduce calculated extents of micelle formation by up to 15 orders of magnitude. Activity coefficients, frequently omitted from the Gibbs equation, are found to increase the calculated surface excess concentration of NaD by up to an order of magnitude. Inflection points in the extent of micelle formation, used to calculate critical micelle concentration (cmc) lowering caused by added salt, provide unexpected thermodynamic evidence for the elusive second cmc.