Arsenic (new) – Periodic Table of Videos

published on July 9, 2020

We're going to tell you about thechemistry of our snake it's afascinating element very poisonouscompounds murders have been carried outwith it it has some very niceconnections with ancient wallpaper andNeal is going to show you a whole series

Of experiments the books say thatarsenic looks metallicbut our sample looked a bit Brown soNeal heated it in a test tube arsenic isinteresting it doesn't melt it sublimeswhen you heat it that is the vapor is

Formed and condenses on the side of thevessel and if you look carefully you cansee it makes a very nice metallic filmoften called an arsenic mirror arsenicis particularly famous as a poisonpeople used it to get rid of their

Lovers their wives or just awkwardpeople and the compound they used isarsenic oxide AAS 406 now we didn't havea sample of this so we decided that Neelwould make some for usso he began by dissolving arsenic in

Dilute nitric acidthere's quite a violent reaction lots ofbubbling and it forms the gas n Ohnitric oxide which is colorless but itreacts with air to give nitrogen dioxidewhich is brown so you can see brownish

Fumes coming out of the test tube thetextbook say that when you dissolvearsenic in nitric acid you make asolution of the oxide we want thepoisonous oxide mint taste of sugar mealset up a very nice filter system poured

The solution in and it came through theymust say it did still look a littlebrown but we were really hopeful we weregoing to get our white powderthe next stage of course is to go fromsolution to solid so you have to

Evaporate off the water it was a bitslow process I got bored and went outwhile Neel was finishing itthat's pure failure what adisappointment instead of this lovelywhite powder there was some sticky brown

Solid I presume because we've still gotsome particles of arsenic in the whitepowder at least we tried but I stillthink it's probably arsenic oxide thereason they used arsenic oxide was theycould easily get it it was a white

Powder it tasted sweet so it wasn't verynoticeable if you mixed it with sugar soour brown stuff is not going to be muchused for poisoning people fortunatelywe're not going to tryI have two favorite stories about

Poisoning both of them are true thefirst one happened in a town in thenorth of England called Bradford ithappened in 1858 in October in thosedays sugar was quite expensive so peoplewho made sweets were very dishonest and

Added some cheap powder to the sugar sothat they didn't have to put so muchsugar in the sweets they called thiswhite powder daft on this particularoccasion a sweet maker called John Nealsent his lodger to go and get some Daft

To put in his next batch of sweets hecall them lozenges and he went to thenext town and went to a pharmacist andthe pharmacist told his assistant to goand fetch the Daft which was a whitepowder and unfortunately he didn't

Explain correctly so the pharmacist sold12 pounds that's five kilos of arsenicoxide to the unfortunate customer thiswas mixed in with a sweet mixture andmore than twenty people died of arsenicpoisoning in Bradford and more than 200

Were really ill and this was one of thethings that led to a greater control ofarsenicin the United Kingdom the other casetook place in the early 1920s in thetown in the West of England called hay

On why the attacks were carried out by asolicitor a lawyer who in fact was theonly lawyer who's ever been hanged inthe UK it is believed he poisoned hiswife with arsenic over a period ofseveral months and then one of his

Business rivals was invited to teathe lawyer passed asked on a little cakein his fingers to his rival and as hepassed it he said excuse fingers and inthat moment it is believed he putarsenic on the cake his guest was very

Ill and was found to have been poisonedwith arsenic so they Exuma buddy of hiswife dug it up and it was full ofarsenic so he was tried and convictedand was executed and it should be saidthat he always denied that he had done

This though when he was arrested he didhave arsenic powder in a packet in hispocket he had nice white powder thequestion is how did they find arsenic inthe body of his dead wife who'd beenunder the ground for several months and

It's with a very clever test that wasinvented in the early 19th centurycalled Marcia's test and Neel decided hewould like to do Marsha's test two thefirst thing you have to do is that addmetallic zinc I was really excited I was

Allowed to chop up the zinc you put inthe pieces of zinc into round-bottomflask and then you add whatever youthink contains arsenic in our case asmall amount of Neal'sbrown sludge

And then from a dropping funnel you dropin dilute sulphuric acid and thesulfuric acid reacts with the zinc andgenerates hydrogen and the hydrogenreacts with the arsenic and makes acompound which has a similar formula to

Ammonia but it has three hydrogen'sattached to arsenic rather than threehydrogen's attached to nitrogen whichyou have in ammonia and this compoundcalled Arsene is very volatile it's agas as the hydrogen streams of the

Reaction it takes the Arsene with ityou'll then meant to light the stream ofhydrogen coming out of the nozzle at thetop of the apparatus if it's justhydrogen coming out it would becolorless and Brady was absolutely

Convinced that we would see a colourlessflame and he could tell us how bad we'dbeen at the experimentmy goodness it works I can't believe aword that's amazing yes you happy yesso the murderers beauty man much to all

Our surprise the flame came out abeautiful lavender color lavender is thecolor that arsenic burns with but thereal elegance of marshes test is that ifyou put a cold surface a piece of glassor a piece of porcelain into the flame

The our scene does not burn completelyso you get a thin film of arsenic on thesurface the importance of this was thatonce the films there it will stay thereso it could be taken to court to beshown as a piece of evidence and you

Could say look arsenic came out of thewoman's stomach or whatever the samplewas that you had there's anothercompletely different way that people inthe 19th century were poisoned byarsenic and that was from the green

Coloring the green pigment that was usedin their wallpaper this green pigment isa copper salt called Sheila's green itis made by taking a solution of sodiummetal arsenite which is colorless anddropping in copper sulphate which is

BlueI've done this reaction several timesbut I haven't done it for a long timeand I was really surprised quite howbeautiful it is saying this green solidforming

Sheila's green was used quite widelythis would been fine except in thosedays people were really frightened ofdrafts and they used to close all thewindows and doors and have very stuffyrooms which were not very well heated so

Particularly at night when they wereasleep there was a lot of condensationand mould would grow on the wallpaperand so the mold growing on yourwallpaper could create a gas containingarsenic which if you were flying asleep

In this airless room over a period ofjust one night would be enough to killyouin October 1815 Napoleon Bonaparte wasbrought a prisoner to the island ofSanta Lena in the South Atlantic yeah he

Was to spend the last six years of hislife yeah he died on the 5th of May 1821examination was made of specimens ofhair said to have been taken from thehead of Napoleon both before and afterhe died the results established the

Presence of arsenic my friend DavidJones who was an expert in really weirdchemical facts wondered whether thestories of Napoleon being poisoned witharsenic by the wicked British could infact be due to mold on the wallpaper in

His house on the island of st Helenawhere he was exiled and remarkably Davidmanaged to get hold of a sample ofNapoleon's wallpaper which had somegreen marks on it and he could analyzethis and show that it did indeed contain

Arsenic and there was enough I'll snakein Napoleon's wallpaper to explain thearsenic that had been found in his hairbut not enough to have killed him soaccording to David's experiments theBritish did not poison Napoleon but he

Just felt unwell because of his greenwallpaper the action of mold on arseniccompound was exploited for realchemistry by an Australian chemist callBruce Wildeand his technician Paul Gauguin they did

A really unique experiment they got somebread and injected it with an arseniccompound that was not volatile and thenput the bread in a large container andlet mold grow on it the mold convertedthe arsenic compound into volatile

Compound gas then they led this througha tube into a solution and they got theyellow solution of a new complex and thereason they used the mold is becauseunlike human chemists the mold couldproduce a so called optically active

Compound that is a left-handed versionof the molecule without the right-handedone whereas ordinary chemists producedboth at the same time and they publisheda great paper and they had anextraordinary photo of Paul the

Technician holding this loaf of breadfull of arsenic I dread to think whattheir safety assessment looked like thispiece of metal has an extraordinarystory about it which involves arsenicwhen I first came here to Nottingham one

Of my colleagues Mike was studying thereactions of arsenic with liquidfluorine if it's done carefully this isa nice controlled reaction you have todo it with the apparatus cooled inliquid nitrogen so he was doing the

Reaction inside a thermos flask thatlooks like this and something went wrongand there was an enormous explosion allthat was left of the thermals was theplastic top and this piece of metaleverything else was distributed around

The lab but I think the importance ofthis is to show you that our snake ifyou get it in the right state or perhapsI should say the wrong state can reactvery violently I went into the labbefore wood had been cleaned up and

Retrieved this because I was just soamazed by it and I used to use it when Iwas teaching about arsenic Kimstring apparently metallic arsenic canoccasionally be found in naturalminerals but usually it's found as

Compounds and in our store we have asample of one of the minerals containingour snake that's called real gar it's anarsenic sulfide which has really verynice red crystals unfortunately oursample has rather small crystals but if

You look at them under a microscope youcan see really nice red crystals whichare of arsenic sulfide and this isprobably why arsenic compounds wereknown even in ancient times because ofthese brightly colored minerals

While we were filming Neel found someamazing old papers lead acetate papersfor testing for arsenic they werelabeled 20th of July 1942 before any ofus were born so we tried these papersout tried testing them on some of Neil's

Mixtures that had madewe were expecting the papers to go blackhowever nothing much happenedwe haven't thrown them away because oneof you may know how to use these papersor we may find out some instructions it

Is said that arsenic was discovered by aGerman Bishop called Albertus Magnus whois buried in the city of Cologne inGermany and about a year ago I gave alecture in Cologne and the students tookme to see his grave and they made a

Couple of little videos of me looking atit not as professional as Brady or Jamesbut still quite funAlbertus Magnus has real significance inCologne to current PhD students there isa tradition that when they graduate

Successfully when they finish theirdoctorates they go to his statue andthey touch his thumb as a sign of goodluck for their future careeryou

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