This enzyme immunoassay for free thyroxin (FT4) involves simultaneous incubation of sample and thyroxin conjugated to horseradish peroxidase (EC 1.11.1.7) in antibody-coated tubes at room temperature. The test can be performed in 90 min. It is not influenced by variations in concentrations of thyroxin-binding globulin (TBG), thyroxin-binding prealbumin, or albumin. With increased concentrations of non-esterified fatty acids, the measured FT4 equivalent concentrations increase immediately, indicating displacement of endogenous thyroxin from its binding sites. FT4 values obtained with this assay for 110 samples, including sera with low albumin and high TBG as well as sera of patients treated with heparin, agreed well with those measured by a two-step radioimmunoassay and with the T4/TBG ratio. The measurable range of FT4 with our assay is 2.5 to 65 ng/L. Intra-assay CVs range from 3.4% to 2.2%, interassay CVs from 6.6% to 2.6% at concentrations of 9 to 45 ng of FT4 equivalent per liter.

Equations of performance ror the bweating operation employed in the manufacture of paraffin wax are derived for the general case of arbitrary initial composition, expressing implicitly the compositions and melting points of the products as functions of the yield, assuming (1) that the components form ideal solid solutions; (2) that the quenched niclting points are mean values; and (3) that the melting poiiits of the individual components are linearly correlated with their respective relative crystallizabilities. For an idealized case, in which the charge is assumed to eontain a continuum of components uniforml? distributed with respect to relative crystallizability , the equations of performance assume a romparatively siniple form. .4 theoretical treatment of the effect of retention of liquid by the melting cake is also given.N THE manufacture of paraffin wax by the sweating process, two effects are sought: the removal of oil and the separation of waxes of different melting points. Both are accomplished by the same type of operation, which is usually applied repeatedly, with more or leas complicated schemes of recycling. At each sta,ge the wax is melted and allowed to solidify by slow cooling, then the east cake is slowly rewarmed, causing partial remelting. The oil and low inelt,ing wax run off as liquid a.nd the higher melting fraction remains behind as solid.No t,heoretical study of the sweating operation has been published and present practice is empirical. This paper presents a mathematical analysis of the opemtion along lines closely following those developed for some distillation problems in a preceding paper ( I ) . PRINCIPLES