ANALYTICAL EDITION 487 types, but which when dissolved at a suitable concentration gives a maximum spread between normal and branched paraffins. Tabulated data covering the necessary number of 10°C.-wide fractions can then be taken once, and the viscosity of an unknown sample determined at a later date concurrently with a control determination on a selected normal paraffin, to correct for resin or polymer aging.
AcknowledgmentOpportunity is taken to thank M. Lapeyrouse of the Esso Laboratories, Research Division, for helpful criticism in con-nection with this work. The authors are also indebted to M. R. Fenske, of the Pennsylvania State College, for supplying the majority of hydrocarbons studied.
determination of the viscosity of liquids at low temperatures presents a number of mechanical difficulties which cannot be overcome without the use of elaborate setups. The main sources of error are due to poor temperature control and also, if a pressure instrument is used, to difficulties in maintaining constant pressure. Since the viscosity of fluids increases very rapidly with decreasing
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