Tutorial: testing alkenes with bromine | The Chemistry Journey | The Virtual School – Video

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Tutorial: testing alkenes with bromine | The Chemistry Journey | The Virtual School
Now it is time to learn about testing for alkenes with bromine - an essential method in organic chemistry. This tutorial will you give the right tips! This v...

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Tutorial: testing alkenes with bromine | The Chemistry Journey | The Virtual School - Video

Calculating reliability, accuracy and precision | The Chemistry Journey | The Virtual School – Video

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Calculating reliability, accuracy and precision | The Chemistry Journey | The Virtual School
Ever wondered what the terms #39;reliability #39;, #39;accuracy #39; and #39;precision #39; really meant? On first glance they may appear to be the same, but this video explains ...

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Calculating reliability, accuracy and precision | The Chemistry Journey | The Virtual School - Video

Bowood House and the discovery of oxygen

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At the weekend I was off on a country jaunt to visit family. We went out to a delightful little pile in Wiltshire called Bowood House. However, despite all the science documentaries I’ve watched over the years that covered, among other things, the history of the elements I was taken by complete surprise when I walked into one of the rooms in the house: this was where oxygen was discovered.
Bowood House, Wiltshire

Bowood House, as it turned out, was where Joseph Priestley spent some of the most productive years of his scientific life in a tiny room-cum-lab only a little larger than a child’s bedroom. While working there in 1774, Priestley used a magnifying glass to focus the sun’s rays on mercury(II) oxide and liberated oxygen from it, naming the gas ‘dephlogisticated air’. This was because the prevailing theory of the time – phlogiston theory – held that substances that could be burned contained the mysterious substance phlogiston, while those that had been burned were dephlogisticated. Priestley was a life-long advocate for phlogiston theory and continued to defend it long after other scientists had concluded it was a dead end. Perhaps giving oxygen a name linking it with phlogiston meant that the theory still held some romantic associations for him.

Sadly, there’s little to show that this room was once one of the most exciting labs in Europe. Now, it merely looks like any other in a stately home with wood panelling, a fireplace and rows of bookcases (one of which is false and leads to the kitchen – a health and safety issue?!). The lab equipment has all gone to science museums, but a few artefacts remain.

RSC & ACS Plaque at Bowood House

— RSC & ACS Plaque at Bowood House

Interestingly, there’s a few letters to Priestley’s chief benefactor of the time, Lord Shelburne. In one, Priestley wrote of a magnificent orrery he had seen costing £1600 (£100,000 in today’s money – science wasn’t cheap way back then either). He then just casually slips in that a sum less than this would fund his lab in its entirety. It seems begging letters for cash for research don’t go out of fashion – plus ça change.

In the former lab you can find a plaque donated by the RSC and ACS, describing it as an international historic chemical landmark. It does, however, rather gloss over his later years, merely saying that he left for the US 20 years after discovering oxygen at Bowood. The truth is a bit sadder. Priestley was living at the time of the American war of independence and the French revolution and was a fan of some of the ideas being codified by these nations, including improved education and personal liberty. This got him labelled as a dangerous agitator in Birmingham, where he was living at the time. In 1794 an angry mob burnt him out of his home and church (Priestley was a Unitarian minister as well as a scientist). It would be more apt to say he fled to the US. Even in Pennsylvania, where he spent his remaining years, his progressive politics were not well received and he spent his time defending himself from scurrilous accusations about his views and home life. Such is the life of dissenter.

Patrick Walter

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Source:
http://prospect.rsc.org/blogs/cw/2013/06/07/bowood-house-and-the-discovery-of-oxygen/

The first French wine

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Archaeologists and chemists have combined their skills to determine that wine production in France may have started as early as 425 BC, inspired by wine imported from Italy.

Ancient pressing platform from Lattara, seen from above. Note the spout for drawing off a liquid. Image courtesy of Michel Py, © l'Unité de Fouilles et de Recherches Archéologiques de Lattes.

— Ancient pressing platform from Lattara, seen from above. Note the spout for drawing off a liquid. Image courtesy of Michel Py, © l’Unité de Fouilles et de Recherches Archéologiques de Lattes.

When most people think of France, they think of good cheese and fine wine (and sometimes a terrible smell), but little is known about when and how winemaking arrived in France.  Now, using a range of chemical analysis techniques as well as traditional archaeological methods, Patrick McGovern from the University of Pennsylvania Museum of Archaeology and Anthropology, Philadelphia, and colleagues have found evidence of wine manufacture in the coastal town of Lattara dating from around 400 BC.

Several clues pointed to this date. Archaeological evidence shows wine being imported in Etruscan amphora, a special type of container, since the 7th century BC, but there seems to be a dramatic decline in imports after around 500 BC – was home production killing the wine import market?

To find out, the researchers examined a site at Lattara (now Lattes), where there is abundant evidence of domestic grape growth.  Previous archaeological digs have discovered amphorae and a stone fruit press, as well as grape remains.  Samples from the amphorae and press were taken to determine if they had been in contact with wine, rather than the altogether more innocuous olive oil, which relies on similar manufacturing and storing processes.  These were then subjected to a battery of analysis techniques, including Fourier-transform infrared spectrometry (FT-IR) and gas chromatography-mass spectrometry (GC-MS).

The analysis of the amphorae showed the presence of tartaric acid, a signature of grapes, along with pine resins and evidence of other botanical additives such as rosemary, basil and time.  This supports the idea that resinated herbal wine (the ancestor of modern day retsina) was being imported from Italy at the time. More significant was the evidence of tartaric acid on the pressing platform, strongly suggesting that it was in use pressing grapes to make local wine as early as 425 BC.

The chemistry is a key chapter in this story, but this tale is not just about grapes and alcoholic drinks. The birth of viniculture in France marked a cultural shift – importing not just a product but plants, expertise, knowledge and culture.  The research itself also demonstrates the results achieved from the bringing together of two cultures – those of chemists and archaeologists.  According to the authors:

“Future biomolecular archaeologists will increasingly be called upon not only to identify biomarker compounds by ever more sensitive techniques, but also to correlate and assess their ?ndings in light of ever more precise archaeological and archaeobotanical data.”

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Source:
http://prospect.rsc.org/blogs/cw/2013/06/04/the-first-french-wine/

Hash chemists could get more than they bargain for

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I’ve been performing some internet searches that could cause red flags in the office, but on the other hand it’s a story of citizen science and lab safety. There is a growing trend for people to perform solvent extractions at home, but what they’re extracting is tetrahydocannabinol, the active ingredient in marijuana, and they’re using highly flammable butane or isopropyl alcohol for the extraction.

— Illustration of cannabis plants. Hermann Adolf Köhler (1834 – 1879)

Now there’s a bit of me that’s quite admiring of these home grown chemists, methodologies are available online and improvements are shared. However, in my experience, the venn diagram of people who are strongly pro-pot and people who are anti ‘scary chemicals’ has a pretty large central cross over. That leads to a lot of discussion about how smoking ‘hash oil’, the resinous product of these home extractions, is ‘more pure’. I’m not sure I agree, it’s still a mixture of compounds rather than pure THC, and despite claims of the oil being 90% THC by these home extractors, my survey of the literature suggests something topping out at 65%. And what about the additives in the solvent itself? But I’m not here to niggle over how good these extractions are, rather to make a point about how a little knowledge can be a dangerous thing.

If you or I, or any chemist who wishes to remain insured, were going to perform a solvent extraction using a flammable solvent we’d write out a risk assessment before we started. We’d think not only about how flammable the solvent is, but also about its volatility, density, health risks etc., and then we’d set out how to minimise all of these risks. If, however, you’re simply following a series of instructions you found online, but you don’t really understand it, it might occur to you to heat up your extract to drive the solvent off quicker. That’s a logical, familiar physical process that people understand from daily life if not from a science class. However, it can make home hash-oil labs go boom.

In February, US agency FEMA, issued a report that hash oil lab explosions are increasing in the US. And when the emergency services turn up to an exploded kitchen they could be hard pressed to  immediately work out whether the tenants were  just after a stronger hit from their hash or making something more serious, like methamphetamine or even bombs.

I love chemistry, and we all perform chemical reactions and solvent extractions in our kitchens every day (hello lovely coffee). But perhaps we ought to remind people of the risks as well, and hope that the people we need to educate are not too stoned to care.

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Source:
http://prospect.rsc.org/blogs/cw/2013/06/05/hash-chemists-could-get-more-than-they-bargain-for/