CobaltChloride
Hazard to Others
Posts: 239
Registered: 3-3-2018
Location: Romania
Member Is Offline
|
|
Materials impervious to hot phosphoric and metaphosphoric acids
So I've heard that heating phosphoric acid to high temperatures makes it lose water and become metaphosphoric acid, which is an excellent dehydrating
agent, but hot phosphoric acid corrodes glass quite a lot. Is there any material more resistant to these acids in these conditions besides
borosilicate glass? PTFE should chemically resist them, but the high temperatures cause it to degrade.
|
|
|
BromicAcid
International Hazard
Posts: 3227
Registered: 13-7-2003
Location: Wisconsin
Member Is Offline
Mood: Rock n' Roll
|
|
Check out this thread on metaphosphoric acid
http://www.sciencemadness.org/talk/viewthread.php?tid=4409
I think there is at least one other as well since everything I remember is not in that thread. Of note is that nickel had a catestropic failure. I
had some success with copper as did another member but there was some attack on the vessel.
|
|
|
CobaltChloride
Hazard to Others
Posts: 239
Registered: 3-3-2018
Location: Romania
Member Is Offline
|
|
Of what I read there, gold plated copper crucibles sound the best. Now I just need to find a good way to do it.
|
|
|
Melgar
Anti-Spam Agent
Posts: 2004
Registered: 23-2-2010
Location: Connecticut
Member Is Offline
Mood: Estrified
|
|
Okay, first of all, the corrosive effect of metaphosphoric acid comes from its similarity to glass. Phosphorus is right next to silicon on the
periodic table, and forms a glassy substance that is slightly miscible with the stuff your glassware is made of. It doesn't exactly eat away at it,
it's more like the substances are similar enough for them to mix a bit at high temperatures.
One solution is just to use cheap glassware, since the glass needs to be near its glass transition temperature in order for this to happen at an
appreciable rate. Beakers and flasks are a couple bucks each when you buy them by the case. You can also use graphite or something, if you have a
ton of money. However... you should try using an aluminum vessel. Hear me out. Aluminum phosphate is one of the most frustratingly insoluble,
unreactive substances there is, and my educated guess is that as long as the aluminum doesn't melt, the phosphoric acid would form a passivating
aluminum phosphate layer.
The first step in the process of learning something is admitting that you don't know it already.
I'm givin' the spam shields max power at full warp, but they just dinna have the power! We're gonna have to evacuate to new forum software!
|
|
|
S.C. Wack
bibliomaster
Posts: 2419
Registered: 7-5-2004
Location: Cornworld, Central USA
Member Is Offline
Mood: Enhanced
|
|
For ethylene from ethanol Weygand (1945) first dehydrates the stirred acid on porcelain, at 160-200C, Weygand/Hilgetag (1972) just heats 85% acid to
200-230C in a RBF and starts dripping in the alcohol. Is the product suitable for methaqualone though you wonder. Who knows.
|
|
|
Texium
Administrator
Posts: 4508
Registered: 11-1-2014
Location: Salt Lake City
Member Is Offline
Mood: PhD candidate!
|
|
Why would you assume that he's
wondering that?
|
|
|
clearly_not_atara
International Hazard
Posts: 2692
Registered: 3-11-2013
Member Is Offline
Mood: Big
|
|
Aluminium's compatibility with phosphoric acid is rated as "C-Fair". Sounds good to me. Will probably develop a patina but continue to work, as long
as you only use the vessel for metaphosphoric acid it's fine.
[Edited on 04-20-1969 by clearly_not_atara]
|
|
|
S.C. Wack
bibliomaster
Posts: 2419
Registered: 7-5-2004
Location: Cornworld, Central USA
Member Is Offline
Mood: Enhanced
|
|
Was it not a perfectly nonspecific you, you being the reader? I wonder, because this is SM. Since you bring it up BTW what other threads has he
started...phthalic anhydride just happens to be 2 steps away from anthranilic acid...
|
|
|
Amos
International Hazard
Posts: 1406
Registered: 25-3-2014
Location: Yes
Member Is Offline
Mood: No
|
|
Quote: Originally posted by S.C. Wack  |
Was it not a perfectly nonspecific you, you being the reader? I wonder, because this is SM. Since you bring it up BTW what other threads has he
started...phthalic anhydride just happens to be 2 steps away from anthranilic acid... |
That's quite potentially because those are two reagents I've been discussing with him a lot in our group conversations on skype. Phthalic anhdyride
I'm buying and selling, and metaphosphoric acid I have interest in for oleum. They're both extremely versatile reagents, I wonder why you thought of
drugs first thing :thinking:
|
|
|
Melgar
Anti-Spam Agent
Posts: 2004
Registered: 23-2-2010
Location: Connecticut
Member Is Offline
Mood: Estrified
|
|
Yeah, I mean, if I wanted anthranilic acid, I'd just buy methyl anthranilate on Amazon and cleave the ester. In the last year or so there have been
some good finds on Amazon. They even had sodium borohydride at a really good price for a while. Got some benzaldehyde too, and even some phosphorous
acid.
The first step in the process of learning something is admitting that you don't know it already.
I'm givin' the spam shields max power at full warp, but they just dinna have the power! We're gonna have to evacuate to new forum software!
|
|
|
CobaltChloride
Hazard to Others
Posts: 239
Registered: 3-3-2018
Location: Romania
Member Is Offline
|
|
| Quote: Originally posted by S.C. Wack |
Was it not a perfectly nonspecific you, you being the reader? I wonder, because this is SM. Since you bring it up BTW what other threads has he
started...phthalic anhydride just happens to be 2 steps away from anthranilic acid... |
I am interested in phthalic anhydride because I consider the oxidation of naphthalene an easy beginner's oxidation and the phthalic anhydride can be
used to make phenolphthalein and some fluorescent dyes. And I want to make metaphosphoric acid because I want to experiment with its properties and
maybe make some oleum. I am NOT in any way interested in making anything illegal. Please don't assume the worst of people before you even have the
chance to know them well.
|
|
|
CobaltChloride
Hazard to Others
Posts: 239
Registered: 3-3-2018
Location: Romania
Member Is Offline
|
|
Anyway, I'll tell you how the aluminium crucible works when I get my phosphoric acid.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
