pH meter

[shocker]

Caustic soda is not hard to come by although its strengths may be variable . I cant see the problem that the PO have with potassium....its sodium that the dangerous one . Anyway , this lot do lab grade sod hydroxide but they do like to make you pay....

http://www.reagent.co.uk/sodium-hydroxide-pellets-ar

...you may want to try the others I listed first .

 

[jamesb]

Sodium Hydroxide is caustic soda. Wilkinsons.

Potassium Carbonate is potash. Garden centre.

Both fairly standard chemicals.

 

[shocker]

Yes , as I noted above - caustic soda is sodium hydroxide , but if Tony is set on his in depth analysis it sounds like he wants to be sure of the relative strengths and purities which can sometimes be a bit variable in hardware store supplies . Me , I would buy from the hardware store and test the reagents first but I was giving Tony some options .

 

[tonyhibbett]

Thanks. I didn't know that. I'll buy caustic soda. How do I mix it for use with titration, and once mixed, what is it's shelf life? I'll compare it with the stuff I have and if I get the same result, that will be brilliant. At up to 7 ml per test, my 114 ml bottle doesn't go far.

 

[shocker]

Titration I cant help you on but I used to mix up small batches of sodium hydroxide/caustic soda as I didnt like having such an aggressive liquid around and I too worried about its shelf life in solution being that its so bloody keen to react with anything it comes into contact with .

So to sum up , I in fact cant help with either and am just typing to keep my fingers warm ..... :party:

 

[jamesb]

So you can measure sulphur dioxide? I have searched in vain for an affordable so2 test kit. Please tell me more!

I've got something on doing this easily but it's in my bookmarks at work. If I remember I'll dig it out on monday.
May as well hijack the thread while I'm here. Would be interested in hearing model recommendations for a pH meter from Tony.

Suplhur dioxide testing:

http://www.bcawa.ca/winemaking/so2use.htm

 

[evanvine]

I have a 0.1N solution of Sodium Hydroxide which I've been using for over 20 years, it still seems ok.

 

[tonyhibbett]

It has to be a decimormal solution, which I assume to be 9 parts water to 1 part dry caustic soda, drain unblocking strength!

 

[tonyhibbett]

Whoops! Should be 100:1. So normal solution of this stuff would be 10:1. Decinormal therefore 100:1, which works perfectly. 1 500g pack of caustic soda will make 50 litres of the solution. Not bad for £2.00, enough for about 10,000 tests, so I made up 500 ml, sufficient for up to 100 tests!

 

[tonyhibbett]

Wrong again. Decinormal does mean 10:1, but the kit I use (RITCHIE) requires a 100:1 solution of the caustic soda from my local grocery store, and has a pH of 10. 100:1 (centinormal?) may not be terribly exact, as I kept on diluting the solution until the test result matched that of the original stuff, but it must be right, because I ended up with 500 ml from 50 ml of the 10% drain unblocker solution.
Either that, or caustic soda may be a far more powerful concentration of sodium hydroxide than what you get in the lab, just as pure heroin is considerably stronger than morphine, by about the same factor of 10. This is possibly true, because behind the pack I bought was another claiming to be even more powerful.
I looked up the link about DIY so2 testing. Obviously I need to find a chemistry teacher, which would have been dead easy when I was working in schools, but those days are long gone. Not an urgent issue as I don't recall having any problems with so2, whereas over-acidity has been a bugbear I'd love to nail. It doen't help when 1 book says acidity decreases during fermentation and another, later, book says it increases. It's like being in a dark cellar, looking for a black cat which isn't even there!

 

[shocker]

QUOTE - "pure heroin is considerably stronger than morphine"

Hmmmm , interesting choice of analogy , Tony :whistle:

Seriously though , an interesting historical field , that of analgesia . Beyer AG developed diamorphine hydrochloride from morphine basically because they could....and then went looking for a use for it . Somewhat like the story of lasers but with more compulsion involved .

As a cure for morphine addiction it was as successful as morphine was as a cure for opium habituation , then as a cure for the common cold it proved a very pleasant alternative to Beechams Powders but not without its side effects . This story trundles along the same vein (hah!) and repeats itself over and over until in the 80s Fentanyl was synthesised which proved to be around 1000 times stronger than pure surgical diamorphine .

You would think someone would have noticed the trend over the 200 odd years that each synthesis caused an exponential increase in problems..... :hmm:

 

[tonyhibbett]

Well, not entirely surprising, ends up being taken over, but that was probably the initial intent. The guys who died working on producing the first plutonium weren't too chuffed that it was used as a mass murder weapon, any more than the brits who passed the info to Russia were somewhat disenchanted about what communism was really about. I even have serious doubts about the global warming stuff promoting more products to sell. Sticking 'smoking kills' on tobacco and raking in loads of excise duty nonetheless. Spirits used to be expensive but now you can pick up bottle of vodka for £8, but the same rate of duty still applies. Huge increase in alcohol related health problems and violence. Fuelling unrest in unstable countries and selling arms to both sides. The list goes on.