Those of you reading this in other countries will ask “How can you still allow chromium(VI) compounds to be used?”. The good answer is that we use “risk assessment” rather than “hazard assessment” and the bad answer is tradition;-we have always done it in this way, it works, why should we change.
But there was a frightening aspect; many of our teachers did not know how to use Quickfit equipment safely. They had not used it for many years (because the previous syllabus did not precisely demand it) and A-level chemistry was being taught by teachers with chemistry qualifications gained as a secondary subject (and not even that sometimes). This outlines the lack the of teacher CPD in practical procedure usually caused by lack of funds.
Once details of the ban of chromium(VI) (and other Substances of Very High Concern ) in Irish schools was known, CLEAPSS, SSERC, ASE with the expert Guidance of the Royal Society of Chemistry met to interpret the EU REACH Regulations which had instigated this ban. The Health and Safety Executive were present and did not “challenge” our interpretation. See http://science.cleapss.org.uk/resource/REACH-and-the-teaching-of-practical-chemistry.pdf which is an open document.
On 21st September2017, the chromium(VI) compounds reach their sunset date and need to have authorisation for their use (Annex XIV). One exemption to Authorisation is for “Scientific Research and Development” under which school use of chemicals is classified by that RSC document. Suppliers may well take different view. There are no other school chemicals with a sunset date other than the dichromates
So from September, it may be very difficult for schools to buy dichromates in the UK.
UK COSHH Regulations do direct employers to adopt safer procedures with less hazardous chemicals if they provide the same results. So does this mean the following?
A green dawn: Fenton’s reagent: a green alternative to oxidation reactions?
I asked some teachers to try this out and comments came back as “did not work” “how old is the hydrogen peroxide” “about 5 years old” “Use fresh”.
Another was disappointed there as there was no colour change and another (and yes, this was said) “It is not dangerous enough”. But compared to dichromate oxidation, this is also a GREEN reagent. It is where modern organic chemistry is and has to go, if we are to satisfy students' and the general publics' concerns about the role of chemistry.
Just look at the results of the atom economy of the reactions.
I went to Brunei to do some courses (as you do) and introduced the idea to a wonderful practical chemist there, Nigel Baldwin. He tried the Fenton method and used a real micro organic chemistry kit that you might like to see it in action. (Note that these are real time videos).
The Fenton’s method is good for extended essays and research. Emily Seeber’s students (http://tinyurl.com/yaywm76h) have recently tried it and got it to work.
It does work with persulfates as well and with propan-1-ol and I would guess popan-2-ol. As with all these oxidising agents, the chemicals do need to be recently purchased.
I do know of other methods such as hypochlorite oxidations but there are exotic co-catalysts and phase transfer reagents involved and as yet these are not on any exam syllabus and expensive in school terms). Perhaps University organic chemistry researchers know different. Yields do not have to be over 90%, for school chemistry, a 50% yield is very acceptable. There are also permanganate oxidations on a quantitative scale but the formation and removal of manganese(IV) oxide is an issue
Even if the there was a halt to supply of sodium dichromate(VI) , I suspect there are enough stocks in schools to enable this practical to be done for many more years.
The idea of altering 100 years of dichromate oxidation in UK schools is virtually impossible; it would need a directive from the UK Health and Safety Executive and they will have enough on their plate with leaving the EU (eyes rolling), or a complete modern review of the syllabus by examiners that want to make chemistry a modern science in schools just as biology is, with its focus on DNA and microbiology, etc. I know from my experience with microscale methods that there is a lot of resistance to change.