If you look at the vapour pressures of various substances, you'll see that 9 orders of magnitude is nothing. And no, an eror in units can't account for that much.
As far as conditions go, I was quotuiing vapour presure off solid. That's it - no conditions to be specified. Vapour presure is an intrinsic property of any solid (or liquid), like density.
Of the metalic elements, the lowest vapour pressure (off solid) is off osmium: 1.41x10-124 Pa @ 300K, the highest is mercury: 3.24x10^2 Pa @ 300K.
Instead of just declaring me wrong, why don't you look up the Antione constants in the CRC Handbook like I did (Sect 4), and the other ref, and calculate yourself the vapour pressure at any convenient temperature.
When you have done the calc, then come back and tell me I got it wrong, and where, should that be the case.
I wish I had a dollar for all the turkeys who assert that something is so, but when challenged to do the calc for themselves, never do so.
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I did quote temperatures - go back and look.
As far as pressure is concerned - well, this is about vapour presure off solid. Vapour pressure of any element or compound is determined by temperature, and only by temperature. Vapour presure is an intrinsic property of any element or compound, independent of whatever pressure it may find itself in.
And you claim to be a chemist, at home using things like PES, EDX? Do you even understand the concept of vapour pressure? Apparently not.
Ah yes, you are the guy who thought there were girls in tube factories applying actual barium oxide from a pot, in air! All that woffle and you didn't even know that single oxides like BaO and SrO are unstable in air.
Better warn those tube factory girls though - Barium Carbonate is poisonous.
What a joke!
How's that 30 minute calculation coming along?
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There's no need. Messrs Claassen, Veenemans, and Becker have measured and reported the physical evaporation rates of BaO and Ba, and this is what is referenced and used by Hermann/Wagener in the plot just posted.
If they are all 'turkeys', well that I doubt. Beats an indirect unpublished calculation based on two sources, which suggests a difference of 9 orders of magnitude in the wrong direction, and which defies the weight of so much credible literature based on BaO as the primary evaporated material .................... 🙄
You're on a sinker, Keit.
Which is it?
Popilin, who has provided some thought-provoking analyses, has pointed out that a simple calculation of emission without regard to fields can be misleading.
By the way, when you (or anyone) cite the Antoine equation, please remember that it is only applicable to pure substances. edit: It is also inapplicable at low pressures.
They are unstable to moisture, not oxygen.
Quite apart from the fact that electron emission from the cathode is just not relevant to the evaporation of Ba from the cathode, as I have pointed out, his guess (It is a guess, he hasn't actually done any calcs, nor does he show understanding of all the terms (Va ??) in the equations he quotes) that electric fields need to be taken into account has no sunstantive basis in fact. The fact is, as any textbook on thermionic emssion will confirm, schottky effect has no applicability to pure metal cathodes, and makes only a few percent difference with oxide cathodes.
Well, strictly speaking, yes.
However, if you actually go look in the CRC Handbook, you'll find that they list constants for the extended Antoine equation, and they give, for each element, the applicable temperature range, generally 298K (~room temp) to the melting point.
I know you don't seem to appreciate it, but if the equation is good over a specified temperature range, then it is good over the pressure range that that temperature range produces. In any case, vapour pressure operates over sunch extreme ranges depending on substance and temperature, the vapour pressure of most substances used in vacuum tubes is essentially negligible by many orders of magnitude. Ba obviously excepted.
We are talking about vacuum tubes - extreme purity is the norm.
Only you mentioned "oxygen". And what do we find in air? Why, moisture of course! And CO2, which is really what is required.
Sy, you are a moderator. Don't you think you should be trying to raise the standard of discussion, instead of following me about trying to score points? Stop and think, and you won't be so easy to knock.
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What credible literature? (apart from the very obsolete H/W)
Haven't done the calc based on Antoine constants (obtainable in CRC handbook and elsewhere), have you?
Untill you do, and post the details, your words mean nothing.
So now there isn't Ba or BaO contamination on the gold grids? My goodness.
My offer to experimentally test grids for deposition is still open.
no need to be harsh to others
i am interested to see your linkedin profile, dare to post link?
I wouldn't normally be as harsh.
But Sy posted first, claiming gold was used because of its work function.
Of course, gold was not chosen because of its work function, as referecnes cited in early post point out. When I pointed that out, Sy elected to continually take shots at me.
Since he takes shots that add nothing to the thread, claims to be a moderator, and since he claims to be some sort of chemist, while being apparently ignorant of relavent chemical principles (he's posted nothing he couldn't have got from a quick dabble in Wikipedia), he's fair game. Sy has a website listed in his diyAudio profile, but it's defunct, so I go on what I see posted in the threads.
As you may note from my diyAudio profile, and my posts in other threads, I am an audio electronic engineer whose later career, due to the 1970's decline in electronics manufacture in Australia, was in utility electric power generation.
I am not in LinkedIn because I have been retired for many years (I'm in my mid 70's) - make of that what you will, but LinkedIn has no benefits to me.
You may care to note that I generally don't just post claims like many do. I back my posts up with logical expanation and/or references.
Some people find being shown wrong no problem and in fact welcome it, some find it annoying, some think it a challenge, some just take it as a personal affront.
I've been checking out the backwaters of gold chemistry, very interesting and peculiar. Seems that several Barium Aurides can be stable, where gold is a quasi anion Au-. Some barium-gold alloys are fairly exothermic to form, and are stable. BaAu, BaAu2, Ba3Au2, BaAu5, marking various bonding states of various stability.
So I continue to wonder whether chemical conversion of BaO and adsorbtion of Ba in the form of an alloy or compound is plausible? Perhaps even adsorption of the oxygen within the lattice as aurate ?
Worth checking out I think, especially with a bit of help from someone who knows the ropes as to what might happen between Ba and Au shells. There seems a possibility that something along the lines of chemical adsorption might happen perhaps, if energy is favourable........
Gold is inert, except in certain peculiar ways.
So I continue to wonder whether chemical conversion of BaO and adsorbtion of Ba in the form of an alloy or compound is plausible? Perhaps even adsorption of the oxygen within the lattice as aurate ?
Worth checking out I think, especially with a bit of help from someone who knows the ropes as to what might happen between Ba and Au shells. There seems a possibility that something along the lines of chemical adsorption might happen perhaps, if energy is favourable........
Gold is inert, except in certain peculiar ways.
I don't know (I rarely buy new tubes any more). I think D3a have them, but there's no way I'm going to sacrifice those!
Not that I can see, no. Although my specialty these days is silicon compounds, our measurement capability has to accommodate all sorts of outside projects.
Sy,
thanks for the offer to test grid wires. I read a data sheet for 6ak5 it said that that the tube has a gold grid. However other 6AK5 data sheets are silent on the matter. I have an unopened case of late 1980's GE JAN tubes. Not sure if there is gold in that there tube or not.
How do we know?
I will be glad to offer two of each for thee three test conditions you listed.
DT
thanks for the offer to test grid wires. I read a data sheet for 6ak5 it said that that the tube has a gold grid. However other 6AK5 data sheets are silent on the matter. I have an unopened case of late 1980's GE JAN tubes. Not sure if there is gold in that there tube or not.
How do we know?
I will be glad to offer two of each for thee three test conditions you listed.
DT
Well, post hoc, the EDX will tell you. Too bad for the tubes that gave their all in the effort.😀
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