1 November 2019 Bulletin

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Nitrobenzene is an organic compound with the chemical formula C6H5NO2. It is a pale yellow oil with an almond-like odour. It freezes to give greenish-yellow crystals. [1] The solid crystals melt at 6 degrees celsius and the liquid boils at 211 degrees celsius. Nitrobenzene is flammable. It dissolves only slightly in water, but mixes well with most organic (carbon-containing) solvents. Nitrobenzene is one of a group of substances known as the volatile organic compounds (VOCs). [2]

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China Opens RoHS 2 Public Service Platform

On 8 October 2019, China Ministry of Industry and Information Technology (MIIT) opened the public service platform for RoHS 2. The platform mainly consists of four functional sections, namely the product conformity query, self-declaration submission, certification submission, and a notice centre. So far, the conformity information of over 1200 products can be searched on the platform. The establishment and operation of the platform is based on the China RoHS 2: Implementation Arrangements for Conformity Assessment System. According to the Implementation Arrangements, Products in the Qualification Management Catalogue (First Batch) for China RoHS 2 that are manufactured and imported after 1st November 2019 shall complete the information submission of the conformity assessment on the platform. Specifically, the certification body shall submit the assessment results to the platform within 5 working days after the relevant product obtains the certification. And the self-declaration with support documents must be submitted to the platform within 30 days after the product is put on the market. Then the contents submitted will be reviewed and published by SAMR and MIIT. There are two submission systems on the platform, one is for suppliers to self-declare the conformity of their products, and the other is for the third-party certification bodies to report the certification results of the commissioned products. For the self-declaration, a guide was published on the platform notice centre to introduce the operation procedures to enterprises. And for the voluntary certification, the most important thing for enterprises is to entrust an authorised certification body. According to the China official information, there are 14 certification bodies authorised for the voluntary certification under RoHS 2. Confirmed product information can be looked upon on the platform through the query function. Recently, MIIT and relevant organisations have held public meetings in several cities to promote the conformity assessment system and the public service platform under RoHS 2 to local stakeholders.


Explained: The lifetime of an evaporating liquid drop

The lifespan of a liquid droplet which is transforming into vapour can now be predicted thanks to a theory developed at the University of Warwick. The new understanding can now be exploited in a myriad of natural and industrial settings where the lifetime of liquid drops governs a process’ behaviour and efficiency. Water evaporating into vapour forms part of our daily existence, creating plumes emanating from a boiling kettle and bulging clouds as part of the earth’s water cycle. Evaporating liquid drops are also commonly observed, e.g. as the morning dew disappears off a spider’s web, and are critical for technologies such as fuel-injection combustion engines and cutting-edge evaporative cooling devices for next generation electronics. Researchers from the Mathematics Institute and School of Engineering at the University of Warwick have had the paper ‘Lifetime of a Nanodroplet: Kinetic Effects & Regime Transitions’; published in the journal Physical Review Letters, in which they explore the lifespan of a liquid droplet. Current theories state that the droplet’s diameter-squared decreases in proportion to time (classical law); however, this period only accounts for a small portion of the drop’s evolution. As the diameter approaches the unobservable micro- and nano-scale, molecular dynamics have to be used as virtual experiments and these show a crossover to a new behaviour, with the diameter now reducing in proportion to time (nano-scale law). Research at Warwick has shown that this behaviour occurs due to complex physics in the vapour flow, which can result in jumps in temperature across just a few molecules as large as 40 degrees! This behaviour is counter-intuitive to our daily experiences (on the macroscale), where we are used to temperatures changing relatively gradually, but must be accounted for to accurately predict the final stages of an evaporating drop’s life. Prof Duncan Lockerby from the School of Engineering at the University of Warwick comments: “The main achievement here is the theory’s ability to quickly predict the drop’s lifetime and create a modelling framework that maintains accuracy from typical engineering scales down to cutting-edge nanoscale applications”. Dr James Sprittles from the Mathematics Institute at the University of Warwick comments: “It is fascinating that intuition based on everyday observations are a hindrance when attempting to understand nanoscale flows, so that, as in this research, one has to lean on theory to enlighten us.


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