pp 719-720 July 2019 Editorial
pp 721-721 July 2019 Science Smiles
pp 725-727 July 2019 Article-in-a-Box
pp 729-734 July 2019 General Article
In 1909, Lewis and Tolman, then physical chemists at theMassachusetts Institute of Technology, wrote a paper whichbuilt on an earlier paper by Lewis. This gave amoremechanicsbasedapproach to the subject, in contrast to Einstein’s originalwork which drew on electrodynamics. This work playeda significant role in the early development of special relativitytheory, then only four years old and still under heated discussionworldwide. This paper with Tolman, though a relativelyminor part of Lewis’s overall work, has historical and pedagogicalvalue and gives a glimpse of his breadth, early growthand influence as a scientist. The present article outlines thearguments of their 1909 paper, and places it in context.
pp 735-740 July 2019 General Article
Oxidation and reduction are two important transformationsin organic chemistry. Although several oxidation and reductionreactions are studied in practical organic chemistry, Birchreduction as an experiment, is generally avoided. It is rathertaught in theory sessions only. There are certain practicaldifficulties and hazards associated with these experiments.Benkeser reduction, however, is a safer variant of Birch reductionwhich can be performed by students under the supervisionof a teacher. Foregoing text is a comparative accountbetween Birch and Benkeser reductions. Additionally, it alsoprovides an experimental procedure to prepare electride saltsolutions which can be employed for a variety of reductions.
pp 741-753 July 2019 Series Article
This article describes simple experiments that showthat honeybees estimate the distance they have flown, by means of ‘opticflow’, i.e., the extent of image motion experienced by theireyes. The estimated distance is then communicated to thebees at home through the tempo of their dance (number ofdance circuits in 15 s) or the duration of the waggle phase ineach circuit. The experiments also provide strong evidenceagainst the previously held view that distance is estimatedby the amount of energy consumed during the flight. Theseexperiments illustrate how cutting-edge research is possiblewith little or no facilities, equipment or money, by asking theright questions, optimizing the design of the experiments andregarding previously fashionable theories with an appropriatedegree of scepticism.
pp 755-765 July 2019 Classroom
Metrizability of Furstenberg topology on integers gives somestrange consequences. Besides a primality test for an integerto be a prime, it shows that primes are not dense in integers.It illustrates the construction of a series of positive numbershaving a negative sum. Furthermore, it re-establishes the factthat the probability of a randomly chosen integer being primeis zero.
pp 767-770 July 2019 Classroom
Planck constant is a fundamental concept in physical sciences,and Millikan received the Noble Prize for determining it experimentallyin 1923. As the technology of solid state electronicdevices developed, an experiment was designed andadapted to determine the Planck’s constant using LED [1,2]. Herrmann and Sch¨atzle  questioned the validity of thisexperiment on the basis of the diode equation, and their approachwas further discussed by Morehouse . In this article,the validity of this experiment is revisited.
pp 771-774 July 2019 Book Review
pp 775-791 July 2019 Face to Face
pp 793-817 July 2019 Classics
pp 819-819 July 2019 Errata
pp 821-821 July 2019 Flowering Tree