Divining: ΥΔΩΡ, Opacity, and Thalean Considerations

Dowsing, water-witching, divining – the procedure seeks a flow or spring beneath the surface of earth. So too this inquiry attempts to locate and sound the meanings associated with the polestar of Thalean considerations, ὕδωρ, that course beneath the interpretative strata of an overly-familiar tradition grounded in the principles of clarity and intelligibility. If these principles are held in suspension, what meanings flow from the Thalean considerations of ὕδωρ? A twofold task guides this inquiry. First is to show opacity as the primary valence of ὕδωρ, challenging the prevailing tendency to imagine Thales and other Milesian thinkers as positing a principle of clarity in the form of what can be brought under the Aristotelean concept of underlying thing and matter (ὕλη). Second, in the course of drawing up the opacity of ὕδωρ form varied archaic sources emerge some connections to important terms for Greek thinking: φύσις, λόγος, ἀλήθεια.

Aging of Elastomers. Comparison of Creep with Some Conventional Aging Methods

Subjection of elastomers to mechanical stresses results in unusually complicated behavior. Recent theoretical researches have shown that this behavior cannot be described satisfactorily by either of the classical theories of elasticity or viscosity. The general molecular theories which describe the behavior of elastomers have experimental verification manifested by three regions of temperature-stress relationship: (1) a low temperature region in which stiffening is observed, due to the stability of secondary bonds between network chains, (2) an intermediate temperature region in which the secondary bonds are so unstable that complete relaxation occurs before measurements can be obtained; the scission of primary valence bonds is occurring at such a slow rate that no measurable effects are obtained during the course of the usual laboratory experiment; and (3) a high temperature region in which the relaxation of stress with time is associated with a chemical reaction which, through breaking of primary-valence bonds in the network, severs the chains rapidly enough to be measured during the course of usual laboratory experiments. The high temperature region is that in which elastomers soften and (or) harden and finally lose their rubbery characteristics. Oxygen has been shown to be necessary for the chain-scission reaction. Several papers have described this fundamental experimental technique for the stress-relaxation and creep of different elastomers. Well known laboratory methods for artificially aging elastomers in oxygen and air bombs and in circulating air atmosphere have selected conditions somewhat arbitrarily. In exploratory searches for promising compounds to be used as antioxidants in elastomers and in the evaluation of well known antioxidants, it has often been found that the conventional methods of aging do not differentiate among several antioxidants. It is the purpose of this paper to describe an application of the previously described creep technique as a convenient and precise means of studying the relative performance of antioxidants and accelerators in Hevea and GR-S rubbers.

Carbon Black-Loaded GR-S Stocks. Relationship between Reinforcement and Swelling Properties

The fact that equilibrium swelling measurements do not show any strong interaction of a primary-valence type between filler and rubber does not exclude the possibility of weaker attractive forces, or such low concentrations of primary valence cross-linkages that they cannot be detected by the methods used. The results of this work indicate that carbon black—rubber systems should be considered as simple physical mixtures. It is hoped that this concept will clarify some of the confusion regarding the reinforcing effect of finely divided powders.

The Fusion Curves of Rubber and Gutta-Percha

It is already known that many rubber-like substances such as elastic sulfur and polyphosphornitryl chloride show crystal interferences when stretched, and that these interferences disappear again when the tension is removed. This shows that the melting point is increased by traction, and von Susich actually determined roentgenographically the relation between the melting point and deformation and thus obtained a “fusion curve.” This phenomenon can be explained by means of the kinetic theory of the elasticity of rubber. According to this theory, the stress set up in rubber when stretched depends on the fact that heat motion tends to restore to the statistically favorable, crooked, and hence shorter form, the primary valence chains which have been extended by traction and thus are in a statistically less probable position and form. For, as a result of free rotation, it is possible to have many curved forms but only one maximum elongated form; the thermodynamic probability β, and on account of the relation: S=R ln β, the entropy S as well, are consequently greater in the unstretched than in the stretched state.

Relation of Volume Change to the Mechanism of Rubber Vulcanization

The present investigation shows that no direct relation exists between either combined sulfur or density and the degree of vulcanization. It is not probable that the various changes in physical properties of the rubber during vulcanization are due to changes in the polymeric state involving a change in primary valence forces. Neither is it apparent in what manner combination of sulfur has contributed directly to the change in physical properties of the rubber. It is probable that the change in physical state is due to a change in manner or degree of aggregation of the rubber molecules.

The State of Rubber in Solutions, Based on the Surface Properties of the Solutions

The problem of the constitution of rubber and especially of its state in solutions has recently again become the subject of active discussion. Based on a series of investigations, Staudinger reached the conclusion that dilute solutions contain free colloidal rubber molecules which are composed of closed chains of an unusually large number of isoprene residues. Pummerer considers the molecular weight of rubber to be much less than does Staudinger. (According to Staudinger the molecular weight of rubber is 50,000 to 170,000; according to Pummerer it is 1200 to 1600.) Meyer and Mark assume for the primary valence chain of rubber a molecular weight of about 5000. These latter investigators are of the opinion that there are secondary aggregates of rubber molecules in a rubber solution and that the high values which were found by a number of investigators (Caspari, Kroepelin, and others) do not represent the molecular weight but the average micellar weight of rubber. In deciding the question of the state of rubber in solution the majority of investigators make use of the classic cryoscopic and osmotic methods of investigation. Staudinger has used viscosimetric measurements in an original way in his experiments. In the present work we have turned to a study of the surface properties of rubber solutions, assuming that data along this line might explain some peculiarities in the structure of these solutions.