Local heat transfer in gravity die casting is of great importance for precision in terms of distortion, mechanical properties, and the quality of the castings due to its effect on solidification. Depending on contact conditions such as liquid melt to solid mold, a gap between mold and component, or contact pressure between casting and mold as a result of shrinkage, there are very large differences in heat transfer. The influences of mold material, mold coating and its influence of aging, mold temperature control, and layout on the heat transfer coefficient (HTC) were investigated experimentally for different contact cases. The experiments were carried out on a rotationally symmetrical experimental setup with modular exchangeable die inserts and cores using an AlSi7Mg0.3 alloy. From the results of the individual test series, the quantitative shares of the above-mentioned influencing variables in the respective effective heat transfer coefficients were determined by means of analysis of variance. From this, the parameters having the most significant influence on the local heat balance were derived.

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A spectrophotometric method is presented for the quantitative determination of poly(viny1 alcohol) (PVA) in contact lens solutions and eye-drops. The method is simple and requires no sample pre-treatment. The procedure is based on the measurement of the absorbance after iron(II1)hydroxamic acid reaction with PVA. The method is useful in quality control and as a screening procedure for solutions considered as PVA-containing mixtures of an unknown type. As the absorbance is dependent of the content of residual acetate groups in the PVA, the type and ester value can be determined. Keywords : Poly(viny1 alcohol) determination ; pharmaceutical dosage forms ; spectrophotometry ; iron(III)hydroxamic acid complexes ANDERMANN et al. IRON(II1) -HYDROXAMIC ACID COMPLEXES I N Analyst, VOZ. 105 Experimental Apparatus cells.