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We have determined this item to be in the public domain according to US copyright law through information in the bibliographic record and/or US copyright renewal records. The digital version is available for all educational uses worldwide. Please contact HathiTrust staff at hathitrust-help@umich.edu with any questions about this item., (LCCN)41005676., (OCoLC)ocm03526357., Sdr-nrlf.b170109136., PZ3.S3158 Can., 828 S315c., Http://hdl.handle.net/2027/mdp.39015063979416.

The purpose of this study was to follow by i.r. analysis double bond shifts and chemical modification of natural rubber. Accurate determination of the original rubber spectrum is facilitated by the use of an internal standard. Isorubber, prepared by thermal dissociation of rubber hydrochloride, contains about 50% of double bonds in the side groups. Although a similar double bond shift is observed in the cyclization of rubber, part of the absorption, in the 11 μ region, may here be due to ring formation. Vulcanization with accelerated sulfur mixtures does not produce changes in the i.r. spectrum, unless the rubber is transformed into a derivative by overcuring with S2Cl2 or during hard rubber formation. At least three types of oxidation reactions can be distinguished spectroscopically: (1 ) degradation of the rubber (by oxidation of a rubber solution with air) with the ultimate formation of only volatile oxidation products; (2 ) gradual formation of oxygenated derivatives (oxidation with ozone), with a distinguishable structure in the spectrum; (3 ) gradual formation of an oxidized and more saturated rubber (oxidation of solid rubber with air), with less characteristic broad absorption bands.

The first part of the article describes the power of special purpose computing registers in solving many-particle interaction problems. Dedicated logic and analog circuits are used in combination with general purpose digital computers to implement specific algorithms in hardware. A significant increase in computational speed can thus be obtained. An example is the fast generation of random numbers for Monte Carlo experiments. Hybrid external processors are able to deliver up to 10 7 truly random numbers per second. The prospects for these hybrid techniques in computational physics are discussed. Modern semi-automatic design techniques with the availability of medium scale integrated components allow a competitive design time for the hardware construction compared to the conventional software implementation. In the second part of the article results are described for a 100 x 100 Ising model, calculated with the algorithm of Yang. Also a model of the growth of crystals in a saturated solution is numerically evaluated by a hardware implementation of a special algorithm.

In an earlier paper spectra of polyisoprenes were discussed. In this communication effects due to the introduction of 1 to 4 chlorine atoms per C5H8 unit are reported. Since an unlimited number of polymers with such empirical compositions derived from isomeric monomer units is conceivable, it seems convenient first to compare some prototypes, then to report in more detail our experience, which is a continuation of earlier work in this field.