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 1 
 on: Today at 09:55:52 AM 
Started by peterschmidt3943 - Last post by Borek
Not sure example of what you want. Reactions taking place are basically like that:

H+ + H2O ::equil:: H3O+

H3O+ + H2O ::equil:: H5O2+

and so on, with a general form of

H(H2O)n+ + H2O ::equil:: H(H2O)n+1+

H9O4+ is just one of these forms - H(H2O)4+.

As these are equilibrium reactions all forms are present in the solution together, so there is no single correct answer to the question "what form does the H+ take in water". Valid question is "which form dominates the solution?" - but the answer depends on the acid concentration and is not easy to determine. If memory serves me well n=3,4,5 are the most often cited values.

 2 
 on: Today at 09:25:45 AM 
Started by SteveE - Last post by SteveE
This is a picture of the two specimens. I simply want to remove some of the quartz surrounding the gold.

 3 
 on: Today at 08:56:31 AM 
Started by peterschmidt3943 - Last post by peterschmidt3943
Hello,

could you give me an example for better visualization?

 4 
 on: Today at 08:53:49 AM 
Started by SteveE - Last post by SteveE
Polypropylene and polyethylene are cheap and they resist many acids and bases, but not heat. +80°C would already be a lot.

Stainless steel should resist NaOH and KOH but not HF. Some cooking sieves are made of it and they resist heat.

The answer to slow etching is crushing to a fine powder. Ball mill?

I want to remove quartz from a couple gold in quartz specimens in situ to expose more gold. Not put the specimens into a ball mill and grind to a fine powder.

Tried to take a couple pictures but I couldn't post them because the files are too big. I'm not quite sure what to do.

 5 
 on: Today at 08:30:17 AM 
Started by peterschmidt3943 - Last post by Borek
Hydronium is a solvated proton, solvation is an equilibrium, multistep process. Technically neither of these two formulas is correct, as solutions contains several separate cations of a general formula H(H2O)n+. Determining their individual concentrations is not trivial, different approaches give different values of n for which the form dominates the solution.

 6 
 on: Today at 07:44:06 AM 
Started by SteveE - Last post by Enthalpy
Polypropylene and polyethylene are cheap and they resist many acids and bases, but not heat. +80°C would already be a lot.

Stainless steel should resist NaOH and KOH but not HF. Some cooking sieves are made of it and they resist heat.

The answer to slow etching is crushing to a fine powder. Ball mill?

 7 
 on: Today at 07:28:59 AM 
Started by pcm81 - Last post by Enthalpy
On aluminium, the method to grow a thicker oxide layer is electricity. It's called anodization. I don't remember of it being used for steel.

On screws, the black layer is mainly FeO and Fe2O3 if not phosphate
https://de.wikipedia.org/wiki/Br%C3%BCnieren (the English article isn't the same process)
https://schraube-mutter.de/schrauben/schwarz-brueniert/
Not very protective against corrosion but very resistant to abrasion. Despite the huge contact pressure, it doesn't rip off. Phosphate give a better protection against corrosion.

I only wonder if any time is meaningfully invested in the corrosion protection of steel.

 8 
 on: Today at 06:59:22 AM 
Started by xshadow - Last post by xshadow
My last sentence should read polar, aprotic solvents (it's amazing what autocorrect spelling will do).  Polar aprotic solvents include DMF and DMSO.  @OP What is the first step of the conversion of an alcohol to an alkyl bromide when H-Br is the source of the bromide ion?


The first step is the protonation of the alcohol.
Then the secondary alcohol gives Sn1
Usually  a protic solvent stabilizes the charged species ,much more. (In alkyl halide as substrate ,  they help the Sn1 mechanism)

Can you tell my why a secondary alcohol gives Sn1 while secodary alkyl halide a Sn2 ?!
Protic solvent help help the stabilization of charge species(usually help Sn1 because I have a carbocatoon and a neutral reagent),but in Sn1  with secondary alcohol  , either the reagent ,the protonted alcohol,  AND the intermediate (the carbocation,for a Sn1) are charged.
So the solvent stabilizes both!!

I need an answer  ..I 've searched everywhere but no answer why  there is this difference.
Thanks.

 9 
 on: Today at 06:58:42 AM 
Started by dvt_texas - Last post by Enthalpy
I know BTU as a heat unit. It can measure many processes, like a combustion for instance. If this is what you're looking for, better search
styrene "heat of combustion"
or "combustion enthalpy"
get the value in whatever unit and convert it in BTU. Example there
http://webbook.nist.gov/cgi/cbook.cgi?Source=1943GUT0R&Units=SI&Mask=F#Thermo-Condensed

 10 
 on: Today at 06:45:11 AM 
Started by peterschmidt3943 - Last post by peterschmidt3943
Hello,

normally, every book describes oxonium ion as H3O+, but some say that it is normally written as H9O4+ ... why?

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