| Pages:
1
..
14
15
16
17
18 |
watson.fawkes
International Hazard
Posts: 2793
Registered: 16-8-2008
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by dann2  |
Procedures in Experimental Physics (book) page 536 describes the process.[...]
Where would one obtain Potassium glass? Make from fused quartz and K compound? |
Oh, you've referenced one of
my most favorite books.
Basically yes. I don't think potassium glasses are readily available in commercial trade. Carbonates are typically used in glass manufacture because
the liberated gas bubbles help mix the melt and drive dross to the surface. Standard flint glass is also made with calcium, whence the lime in
soda-lime glass. So raw materials are silica of some form (the purity of fused quartz might not be necessary), potassium carbonate, and lime (or the
carbonate). Other additions, if you want a more refractory glass, can include alumina and borax. After that, you'll need to work it into a vessel,
which more or less means blowpipe work. Not exactly a quick project.
Then again, neither is the procedure in the book. You first seal on a tube to a light bulb and evacuate argon with your trusty vacuum rig. Then you
use a power supply that provided both (1) arc voltage from one side of the filament to the bulb immersed in the sodium salt bath and (2) a DC bias
from the other side, which provides your electrolysis current. Electrically, this device is much like a tube diode with the heater filament and
cathode combined. You heat the bath to melt the sodium salts and turn the glass into an ionic conductor. You blow air on the top of the bulb to make,
essentially, a reflux condenser that's cold enough so that the reflux solidifies. To answer the question above, it seems that it's ambient air, but in
rather high volume.
The reference given is "Burt, R.C., J. O. S. A., 11, 87 (1925)", but I don't know offhand what journal that is.
|
|
|
dann2
International Hazard
Posts: 1523
Registered: 31-1-2007
Member Is Offline
Mood: No Mood
|
|
Hello,
I photographed some pages of the book and attached.
This link:
http://www.lenntech.com/periodic/elements/k.htm
says television tube glass is Potassium glass. A large 24 inch TV tube should be large enough of a 'bulb' (at least to get started  )
Dann2
BAN THE BULB, BAN THE BULB, BAN THE BULB, BAN THE BULB, BAN.....
Attachment: PEP_Stong.zip (1.3MB)
This file has been downloaded 1168 times
[Edited on 23-9-2009 by dann2]
|
|
|
S.C. Wack
bibliomaster
Posts: 2419
Registered: 7-5-2004
Location: Cornworld, Central USA
Member Is Offline
Mood: Enhanced
|
|
With the NaNO3 being 350C, not very. I'm unaware of any incandescent light bulbs under vacuum; which seems to be a requirement, for sublimation if
nothing else.
|
|
|
watson.fawkes
International Hazard
Posts: 2793
Registered: 16-8-2008
Member Is Offline
Mood: No Mood
|
|
It says that potassium goes into the making
of glass for television tubes. There's potassium oxides in ordinary container glass, as a rule. So while we might expect that this TV tube glass is
higher in potassium content that other glasses, that doesn't mean it's going to be free of sodium. Then again, this question really only addresses the
purity of the final product. It's fully likely that you'll get ionic substitution in the glass and sodium contamination, but that may not matter,
depending on what you're aiming for.
Nevertheless, if you're serious about this, I would recommend that you first duplicate the sodium electrolysis, since there are already enough moving
pieces to get right, even with a known-good example.
|
|
|
12AX7
Post Harlot
Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline
Mood: informative
|
|
I wonder if the sodium and potassium ions melt at different temperatures.
(Notice ion mobility == phase change of just one part (not the silica lattice), in the same way that many ceramics are liquid phase sintered while
retaining their overall structure.)
Tim
|
|
|
vulture
Forum Gatekeeper
Posts: 3330
Registered: 25-5-2002
Location: France
Member Is Offline
Mood: No Mood
|
|
| Quote: |
I have not seen 1kW PSU on the market. At 12V they would be useless for electrolysis - at 5V they would be OK. |
You can order them from any decent supplier nowadays. PC PSU's will also provide 5V and 3.3V with quite beefy amperages, so you can choose.
http://www.coolermaster.com/product.php?category_id=24&p...
That model is capable of delivering peak currents of 40A on both 5 and 3.3V
[Edited on 23-9-2009 by vulture]
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
|
|
|
hinz
Hazard to Others
Posts: 200
Registered: 29-10-2004
Member Is Offline
Mood: No Mood
|
|
Look for the HP 6260B PSU at E-bay It can supply 100A DC at 0-10V. Probably better than any PC PSU, cause the voltage can be regulated to the needs of
the cell. Futhermore these beasts are no Switching PSUs, they're based on a tyristor preregulated transformer, so ther're no MOSFETs to go bad.
There're also other HP 62xx PSUs around, some of theulra heavy ones can supply even more than 100A DC.
|
|
|
watson.fawkes
International Hazard
Posts: 2793
Registered: 16-8-2008
Member Is Offline
Mood: No Mood
|
|
An excellent question. Each exists
in glass as the oxide. I'd have to say, if I were pressed to guess, that K2O melts first, simply because K has a free 4s electron with a lower
ionization energy than Na with its 3s one. It seems to me that the activation energy would be lower in this case. It's likely, though, that there's no
discrete phase change associated with these states, having a solidus/liquidus range where there are blended phases.
In this case, however, I'd guess that it's not phase transition that dominates, but instead ion mobility. Here smaller ions have a definite advantage.
Potassium is going to move through any ionic conductor less readily that sodium. Offhand, I'd say that the phase partition between K and Na, even if
it favors K, isn't enough to overcome the Na size advantage.
Having said all this, it seems far more interesting to try this, not with potassium, but with lithium. Lithium is going to be a better ionic conductor
even than oxygen, and second only to hydrogen. The special glass would be made of silica-lithia-calcia, that is, lithia-lime glass. If temperature of
the salt bath were controlled appropriately, it's possible that this makes a decent electrowinning process for refined, but not purified, lithium
salts. There's some optimum rejection temperature above that where Li(+) becomes significantly mobile but below that where Na(+) does.
|
|
|
densest
Hazard to Others
Posts: 359
Registered: 1-10-2005
Location: in the lehr
Member Is Offline
Mood: slowly warming to strain point
|
|
Well, Google turned up an 1887 receipt book containing the instructions to grind up lepidolite, roast it for some hours, then melt it and use it as a
glass... KLi2Al(Al, Si)3O10(F, OH)2, Potassium lithium aluminum silicate hydroxide fluoride. A violet to pink mica, Notable Occurrences include
Brazil; Ural Mountains, Russia; several African localities and California, USA. If I can get hold of some I will try to blow some bubbles; dunno what
melting point would be. If it worked, then one would have both Li and K glass in one go. The 1925 article did say that the bulb needn't be evacuated
if I read it correctly - dunno what gases might have been used for fill then - more history to look up.
There were a number of lithium-containing glass formulas showing up in the search but all of them had large amounts of sodium in them which might or
might not be bad. It would be tempting to substitute lithium into the formula for 7720 glass, but the article says that borosilicate glass didn't
work. Pity, a low-thermal-expansion glass is much easier to work.
Now, how to find a chunk of lepidolite which is sufficiently pure to give a useful glass but not so beautiful as to be a sacrelige to melt?
|
|
|
watson.fawkes
International Hazard
Posts: 2793
Registered: 16-8-2008
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by densest | | If it worked, then one would have both Li and K glass in one go. The 1925 article did say that the bulb needn't be evacuated if I read it correctly -
dunno what gases might have been used for fill then - more history to look up. [...] There were a number of lithium-containing glass formulas showing
up in the search but all of them had large amounts of sodium in them which might or might not be bad. |
As for
making glass, look up "batch glass" in the art glassblowing world. It's typical for those folks to mix up their own glass compositions. There's plenty
of information on it. Note: lithia is an aggressive alkali in molten form, meaning it will attack crucibles, particularly those with high silica
content, readily. I'm not familiar with materials compatibility here, but I'm sure there are issues. And in any case, definitely do a tiny melt before
a large one.
As far as evacuation, you need the right gas pressure to sustain a discharge. Now I said arc discharge before, but that's probably not right. Glow
discharge is likely the right regime. The book mentioned sodium vapor discharge, which would certainly happen once the electrolysis and sublimation
started. It also mentioned argon discharge, which may be what happens at the beginning. Whatever the actual pressure is, it interacts strongly with
what the power supply has available to ionize gas. The supply supply should have an appropriate ballast circuit to limit current once the discharge
starts.
Edit: I found the original article
Journal of the Optical Society of America, volume 11, issue 1
http://www.opticsinfobase.org/josa/abstract.cfm?uri=josa-11-1-87
SODIUM BY ELECTROLYSIS THROUGH GLASS RELATED EXPERIMENTS ON FARADAY’S LAWS, SODIUM ARC AND RESONANCE RADIATION
by ROBERT C. BURT (of Cal Tech)
[Edited on 24-9-2009 by watson.fawkes]
|
|
|
densest
Hazard to Others
Posts: 359
Registered: 1-10-2005
Location: in the lehr
Member Is Offline
Mood: slowly warming to strain point
|
|
@watson.fawkes - yes, I'm at least theoretically familiar with glass production - I do flameworking and have made gold-ruby and silver-multicolor
glass in the flame from clear boro and metal/metal compounds. The biggest problem is crucibles; no matter what you use, molten glass eats it. I have
some BN powder spray which seems to be inert up to about 1600C which might protect a small crucible as long as the atmosphere was not strongly
oxidizing. The most promising idea from my point of view (small batches, occasionally) is an induction furnace since once hot, glass becomes
sufficiently conductive to absorb electromagnetic energy strongly. That has the advantage that the crucible is relatively cool and the batch
self-insulates. One would have to initiate heating with a torch to melt a blob in the center of the crucible and let that heat the rest from the
inside out. I can make high power electronics from parts on hand. Crucibles I have to buy and I'm on a very very tight budget for new acquisitions. I
have some alumina crucibles of the right size which would probably get eaten out during the first melt if they were heated from the outside. They
might hold up if the highest temperature molten glass didn't touch them.
The curse of the "new age" has hit yet another mineral. Lepidolite is purported to have all sorts of wonder peaceful principles so it is in demand for
charms and fetishes. Still, there's a place which sells it for $12/pound with the pictures appearing to be of reasonably pure mica, so that's a
possibility. Reade Materials advertises that they sell it - anyone ever dealt with them? A railroad car load is a bit more than is necessary.
If I -can- make a melt of this, I can probably make 5-8 cm spherical bubbles - would anyone be interested in one if I make them? Doing just one or two
seems to be a waste of prep time... I'll also try melting some Corningware (tm) which is at least partially Li (probably a lot of Na too, don't have
the formula.)
All this is moot if anyone finds prefabricated useful shapes of Li glass...
|
|
|
not_important
International Hazard
Posts: 3873
Registered: 21-7-2006
Member Is Offline
Mood: No Mood
|
|
Just buy the oxides/carbonates needed for the glass at a pottery supply, don't try to find lepidolite.
|
|
|
watson.fawkes
International Hazard
Posts: 2793
Registered: 16-8-2008
Member Is Offline
Mood: No Mood
|
|
I've had something of an insight about this. It's possible that you don't need to start with a glass of any particular composition if (big if) you are
willing to run it through an initial period and/or tolerate some contamination at the beginning of the campaign for the apparatus.
The electrical current in this system travels through three media: the gas fill from the cathode to the inner surface of the glass, the glass itself,
and the salt bath. In the gas, the current carriers are free electrons and the alkali ions in plasma. In the salt bath, they are electrons and alkali
ions in solution. In the glass, however, I believe that major negative current carriers are oxygen ions, with some small portion of electrons. While
the net model is that of alkali ion diffusion through the glass, an individual alkali ion would travel only slowly through the viscous, hot glass. The
alternate activity is that the alkali ions are combining with oxygen at the outer surface of the glass and dissociating from it (reducing) at the
inner surface. It's easier for an oxygen atom to move from a neutral atom to a newly arrived alkali than for that alkali ion to move under the
influence of the electric field. On the other side, free electrons reduce alkali atoms in their oxide, making space for new alkali to diffuse to the
surface, tugging on a diffusion chain for the alkali current. So the oxygen current corresponds to this hopscotch kind of net motion. There will also
be some direct diffusion because of the electric field; this corresponds to the electronic current.
The upshot of all this is that, if the composition of the alkali salt bath doesn't match the alkali composition of the glass, then the composition of
the glass will change over time by ionic replacement. The most easily reduced ions will come off the surface first, so potassium before sodium before
lithium. Among other things, it means that if you use it for lithium, you'll need to purge the glass of its free sodium (which may be all the sodium;
I don't know).
If this idea is true, it should be easy enough to test by running an ordinary soda-lime glass bulb in a lithium bath and running an assay in the
initial product. There should be a mixed product of sodium and lithium, with sodium initially dominating.
|
|
|
Helgoland
Harmless
Posts: 4
Registered: 30-12-2009
Member Is Offline
Mood: Tired
|
|
Crown ethers?
Sorry to revive an old thread, butI've been thinking a bit. If I annoy you, I'll stop.
Crown ethers are cyclic ethers that can form complexes with cations and so act as PTCs.
I was thinking water at the anode, aprotic solvent with crown ether at the cathode.
I couldn't find anything on their electrolysis though.
Crown ethers are quite expensive, I think. Maybe polyethylene glycol (with methyl groups at the ends, called podands) might do the job as well.
What do you think?
Helgoland
EDIT: Here's another good link (in german) on host-guest-systems in general.
[Edited on 26-5-2010 by Helgoland]
Happiness is a matter of attitude.
|
|
|
The WiZard is In
International Hazard
Posts: 1617
Registered: 3-4-2010
Member Is Offline
Mood: No Mood
|
|
An interesting case of soil electrolysis of sodium
Noted in passing. You will forgive if this is not new, I am
not going to read 7-years of posts ......
The Journal of the Society of Chemical Industry
No.5 Vol. XXVI,. March 15, 1907.
Liverpool Section.
Meeting held at the University, on Wednesday, December 12,1906.
DR. JAMES T. CONROY IN THE CHAIR.
AN INTERESTING CASE OF SOIL ELECTROLYSIS WITH FORMATION OF A
LIQUID SODIUM POTASSIUM ALLOY.
BY HENRY BASSETT, JUN.
Now that electricity is so largely used for lighting and power purposes, and wires
conveying the current traverse the ground, especially in towns, in all directions,
the effects of wandering earth currents, due to leaks from the wires, and earth
returns on tramway systems, occasionally attract attention. These earth currents
usually manifest themselves by causing the corrosion of metal objects, such as
pipes, tramway rails, &c., placed in the ground. In such cases the object attacked
acts as anode, the surrounding earth being the electrolyte. In other cases, where
we are dealing with the opposite end—that is to say, the cathode—of the huge
Voltaic cell thus formed, alkaline deposits are found.
The following case, which was brought to my notice some months ago, may be
of interest, as it shows the magnitude of the chemical processes which may be
caused by such earth currents. On March 6th a bad " earth " occurred at the
Brownlow Hill Workhouse, Liverpool. The leak occurred just under a small
roadway, and although the cable had probably been failing there for some time,
the leak was only discovered from the fact that horses became restive at that
spot owing to shocks which they received, and which, in fact, one could get by
touching certain places. The cable affected was one supplying power to a motor
at 460 volts. The current was carried by two thick insulated copper cables (a
negative and a positive). These were laid about an inch apart on wooden
bridges, in a wooden trough, which was then filled with bitumen, a wooden lid
being finally laid over the bitumen. This trough was buried in porous sandstone,
the top being about 18 inches below the surface of the ground. The leak had
possibly been started by a heavy cart causing a crack in the bitumen, through
which water had penetrated to the cable. Only the negative cable (which would
be at 230 volts below the potential of the earth) was affected. This cable had
been joined at the place where the leak occurred, the join having been bound
round, perhaps not very carefully, with waterproofed cloth.
According to the clerk of the works, under whose directions the leak was
repaired, the material surrounding the leak was still so hot that one could only
just touch it, although the current had been switched off for an hour and a half. It
was found that the top of the wooden trough bad been burnt through, and that a
hard substance protruded through the hole thus formed and penetrated to the
wire. This substance was so hard that it had to be removed with cold-chisel and
hammer, and the workmen, to their surprise, caused big sparks during the
operation. They also got rather burnt under the finger nails and on the face by
flying chips of the evidently strongly alkaline material. The hard lump had been
formed round the negative wire, but the metal was not at all corroded, neither
had the insulation of the neighbouring positive wire been affected. The
substance removed from the leak was collected, and the engineer, Mr. A. J.
Wilson, who had been much struck by its curious properties, asked me to
investigate it.
The pieces brought me were dark grey in colour, very hard, very deliquescent,
and strongly alkaline. If treated with a little water, small yellow or lavender flames
were formed by bubbles of hydrogen catching fire. The mass evidently contained
free alkali metal; in fact, on breaking a piece of the hard substance, the crevices
in the interior were found to be filled with bright liquid metallic globules, evidently
a liquid alloy of sodium and potassium. When these globules came in contact
with water they ignited, although the viscous alkaline liquid, with which the lumps
of the grey mass soon became covered on exposure to the air, had very little
effect on them. Analysis of the hard grey substance showed it to consist chiefly
of potassium and sodium hydroxides, with a certain amount of the free metals.
There was also a considerable amount of sand from the surrounding sandstone,
as well as some silica rendered soluble by the action of the alkali, which must
have been nearly fused during the passage of the current. It was quite free from
carbonate, sulphate, chloride, &c., neither did it contain any metals other than
sodium and potassium. A quantitative analysis gave the following results: KOH,
33.37; NaOH, 32.26; K, liquid alloy 1.00 ; Na, liquid alloy, 0.80 ; soluble silica,
4.80 ; sand and earthy matter, 26.36; bitumen and water (by diff.), 1.41; total,
100.00 per cent.
The determination of the free metals was carried out by measuring the amount of
hydrogen evolved when a given weight of the substance was decomposed with
water in a graduated tube over mercury (0.312 grm. substance gave 8.4 c.c.
hydrogen at 19o and 470 mm. pressure). Knowing the total amount of potassium
and sodium in the substance, the amount of the liquid alloy and its composition
can then be calculated. The composition of the alloy, as calculated from the
above analysis, is 55.6 per cent. potassium and 44.4 per cent. sodium.
According to the researches of Kurnalrow [1], such an alloy would be liquid at
temperatures above 7o C.
The formation of alkali by the electrolysis of the salts dissolved in surface water
is, of course, not very surprising, but the quantity formed in the present case is
rather astonishing when it is considered what a very small amount of potassium
and sodium salts are present in soils. I had in my possession pieces of the
alkaline mixture weighing in all 570 grms., while from what I was told probably
not less than 1000 grms. had been formed altogether. The surrounding bitumen
for a short distance was also more or less impregnated with alkali.
If the leak had not been discovered, but had been allowed to continue, as often
happens in such cases, the alkali would have eventually destroyed the insulation
of the neighbouring positive wire and have caused a " short circuit."
The alkali was of course formed by the potassium and sodium first liberated by
the electrolysis reacting with water. This must have caused the evolution of a
large amount of hydrogen. If this gas had been evolved in any position in which it
could have accumulated and have got mixed with air, a violent explosion could
quite easily have been caused, either by a light being brought near or simply by
a globule of the liquid sodium-potassium alloy coming in contact with water and
causing a spark. Many of the explosions in connection with electric light mains,
usually attributed to accumulations of coal gas, are very possibly in reality due to
hydrogen formed by electrolysis--a suggestion which was first put forward by Mr.
Foulger at the Board of Trade inquiry into the explosion which occurred in the
conduit of an electric light main in the Euston Road; London, on Dec. 29, 1895.
[2]
It seemed pretty certain that the alkali formed in the present case had come from
the surrounding soil and sandstone, but as it was just possible that it had come
from the bitumen, this was analysed. A piece of the same bitumen as that which
had been used in laying the cable gave on ignition 33.2 per cent. of ash, and the
amount of alkali extracted from this by boiling with concentrated hydrochloric
acid corresponded to 0.18 per cent. potassium oxide and. 0.37 per cent. sodium
oxide in the bitumen. Now as the total weight of bitumen removed during the
repairs, and which might possibly have had its alkali removed, only amounted to
about 1200 grms., 6.7 grms. of mixed alkali is the maximum obtainable from this
source. However, it is much more likely that none of the alkali had come from the
bitumen, for to all appearance this had been very slightly affected. A small
amount of potash might likewise have come from the wood of the trough in which
the cables were laid, but the amount of this would be still more insignificant than
that which could have been derived from the bitumen. It is therefore clear that
the alkali could only have come from the surrounding soil.
The sandstone in which the cable was laid was seen under the microscope to
consist practically entirely of rounded quartz grains, and, as was to be expected,
was found to be very poor in alkali. The alkalis, which were extracted by boiling
with concentrated hydrochloric acid, were determined in a piece of sandstone
which was obtained from a spot at some distance from the Beene of the " earth,"
so as to avoid any possible contamination with the alkali which had been
accumulated there. This sample of sandstone contained only 0.047 per cent. of
potassium oxide, and 0.016 per cent. of sodium oxide. The thin layer of surface
soil contained a slightly higher amount of alkalis, which were also present in
rather different proportions, viz. : 0.056 per cent. of potassium oxide, and 0.055
per cent. of sodium oxide.
Although these quantities are very small, the volume of ground from which they
could accumulate was practically unlimited, and the amount of alkali found round
the " earth " could all have been obtained from about a third of a cubic metre of
the sandstone. Taking the specific gravity of the latter as 2.7, this quantity would
weigh 900,000 grms. and would yield 630 grms. of alkali, whereas about 660
grms. were actually formed in the present case. The same amount of alkali could
have been obtained from about a fifth of a cubic metre of the surface soil. It will
be noticed that the relative proportion of the two alkalis in the surface soil is
exactly the same as in the hard alkaline material formed round the " earth." It is
therefore probable that the alkali accumulated at the latter had been almost
entirely derived from the surface soil, and only to a very slight extent from the
underlying sandstone.
It should be mentioned that a few days before the occurrence of the above "
earth " the weather had been moderately dry with, however, occasional pretty
heavy rain.
Another case of alkali formation.—When I mentioned the above case of
electrolysis to Professor Marchant, he told me that he had recently been having
some trouble with some of the switches on the basement walls of the
electrotechnical buildings of the University of Liverpool. White efflorescences had
been forming on these and causing trouble. Professor Marchant gave me some
of the efflorescence from one of the switches, and an examination showed that it
was simply a mixture of 42.66 per cent. of potassium carbonate, and 12.02 per
cent. of sodium carbonate, together with water and a small quantity of alumina
and silica. It was only the switches on the negative wires which were thus
affected. It is plain that moisture had crept through the walls from the outside
soil, and finally on reaching the switch, electrolysis of the dissolved salts had
occurred. Potassium and sodium hydroxides had thus been slowly formed, and
carbonated by the action of the atmospheric carbon dioxide. The formation of
this efflorescence had been noticed for about two months, and by the end of that
time it had become so bad that the switch had to be removed and replaced by a
new one. It may be mentioned that this switch was placed against a concrete
wall which was below the ground level, but tarred on the side in contact with the
earth. The ratio of potash to soda quite, different to that found in the case of the
workhouse " earth," although the spots at which the two cases of electrolysis
occurred are only about 200 yards apart.
It is well known that the insulation of a positively charged wire tends to improve,
while that of a negatively charged one nearly always deteriorates. [3] This is due
to the phenomenon of " electric endosmose," which drives the moisture (or
electrolyte) away from the positive wire and towards the negative wire. This
action can be observed in an ordinary electrolytic cell. If the cathode is enclosed
in a porous pot, the level of the liquid in the pot gradually rises above the level of
the surrounding liquid. This is what is usually observed, but cases are also
known in which the effect takes place in the opposite direction. The force tending
to drive liquid through such a porous partition is proportioned to the difference of
potential between the two sides of the partition, and may be very great.
Insulated wires placed in the soil are subject to similar forces, and, as mentioned
above, the insulation of a positive wire improves. Any weak spot in the insulation
of a negative wire is, however, soon broken down, and moisture reaching the
wire, a leak is started. The insulating material may be regarded as a very slightly
porous partition, and in some cases it has been found that leaks may occur
without any mechanical break in the insulation, electrolysis also occurring with
formation of alkaline liquids under pressure between the insulation and the wire.
It appears that on account of this " electric endosmose " about 99 per cent. of the
faults which occur on direct current networks occur on the negative wire. At all
negative faults alkaline deposits or solutions are formed, and although it is
known that these usually contain potash and soda, in only one or two cases do
careful analyses of the products appear to have been made. In certain rare
cases also the formation of free alkali metal has been observed.
The first record of such a case that I have been able to find is in a letter to the
"electrical World" of July 6, p. 5, 1889, in which an account of an "earth" in
Boston, U.S.A., is given. The "earth" in many respects was similar to the one
recorded in the present note, for the cable affected was embedded in bitumen
and a hard lump was found at the fault, which flashed when wetted.
Another case of the kind does not appear to have been noticed until 1895. In
February of that year a serious explosion occurred in Euston Road in one of the
conduits of the St, Pancras electric-light system. Major Cardew, during his
investigation of the affair for the Board of Trade, found incrustations on some of
the insulators supporting the bare copper strips by which the current was caried.
These incrustations gave sparks with water, and were found to contain free alkali
metal, and from a statement in an editorial note in the " Electrician," [4] it is plain
that a fluid potassium sodium alloy had been formed, as the metal is described
as occurring in globules almost as fluid as mercury. As a result of Major
Cardew's discovery a committee was formed to investigate the causes of the
formation of these alkaline deposits. When the committee inspected the St.
Pancras mains (not quite at the place the explosion occurred), they found an
incrustation which flamed on treatment with water, but which in this case
contained solid (not liquid) alkali metal. In the Committee's report is an analysis
of the incrustation found on the cables near where the explosion occurred, as
follows :—Sodium hydroxide, 7.69 per cent. ; potassium hydroxide, 4.88 per
cent. ; sodium carbonate, 34.40 per cent. ; potassium carbonate, 52.77 per cent.
; also traces of silica, alumina, and lime. There appears to have been no free
metal in this incrustation at the time of analysis.
Since 1895 numerous cases of alkali metal formation have been noticed, but I
have not been able to find any other mention of an occurrence of the fluid alloy,
nor any other analysis of the alkaline incrustation.
The second case of electroysis described in the present note is rather a striking
illustration of the respective behaviour of a positively and negatively charged
insulated wire in presence of moisture. It was explained how the insulation of the
negative switch broke down owing to alkali formation. Now, although the positive
switch was placed in an exactly similar position to the negative one, no signs of
electrolytic action were shown by it, and although at only a short distance from
the negative switch, the leak from the latter did not follow, as might have been
expected, the short direct path to the positive terminal, but went a roundabout
way to the soil, and then, probably, to some tramway rail several hundred yards
away.
Discussion.
The CHAIRMAN said it must always be borne in mind that rubber was a very
perishable substance, and that, whilst new rubber might be absolutely
impervious to water, even under the influence of the current, partially perished
rubber might behave like a porous substance. The phenomenon of electric
endosmose possessed very great interest. It had found practical application in
the patented methods of drying peat by aid of the electric current, and, from what
Mr. L. Hargreaves had told him, it was not without influence in the successful
working of the Hargreaves diaphragm.
Prof. E. W. MARCHANT said that the general character of these faults had been
known for a considerable time. In Paris and St. Pancras, faults almost identical
with those Dr. Bassett had described had come to light, but they occurred in
mains laid in earthenware troughs, not in mains laid in bitumen, on what was
known as the solid system. The case named by Dr. Bassett appeared to be the
first one that had been described with mains laid in bitumen. A recent experiment
by F. Fernie, which showed the way in which such faults might be produced, was
this:—One of the highly-glazed earthenware tubes that were used for carrying
conductors was buried in the ground, the lower end embedded in bitumen, and
the urper end about 2 ins. above the level of the ground; a coil of wire was round
the outside of the tube, and another round the inside. Water was first poured on
the ground round the tube in large quantities, and the tube left for 14 days. The
inside remained quite dry showing that the tube was perfectly water-tight. The
two wires were then connected to a lighting circuit of 230 volts pressure the
inside being made negative to the outside wire. After an hour or two, drops of
moisture appeared on the inner side of the tube, and after two days the tube was
half-full of water. On reversing the polarity of the wires, the tube ultimately
became quite dry again inside.
That gave a very good idea of tre actual force due to endosmotic pressure,
which tended to produce faults on a negatively-charged main ; it was astonishing
that the force was as big as it was.
Of course, the greater number of faults did occur on the negative main. The ratio
of faults was something like 100 to 1 ; for example, in comparing continuous
current networks with alternating current networks, wherever there were faults on
a d.c. system, they almost always occurred on the negative side. As to the cause
of the explosions which sometimes occurred in conduits containing electric
mains, he did not think they were often due to the electrolytic production of gas.
The amount of leak from ordinary gas-pipes was enormous. The efficiency of a
gas system was very low. If the meters of the consumers registered 80-90 per
cent. of the amount registered at the station, the gas company considered that
they had done pretty well. If there were a spark from any cause independent of
electricity, which would ignite the gas, an explosion would occur. In laying
cables at the present time, the greatest care was taken to make the pipes as
tight as possible, to prevent any gas leaking into them. It was only where there
were drawn in mains with leaky service-boxes that there was risk of ordinary
town gas leaking in. With reference to the rubber cables, he had never come
across a case in which there was an accumulation of water inside a cable, nor
had he ever known a perfectly insulated rubber cable act as a porous substance.
Dr. BASSETT, in reply, pointed out that the second case of electrolysis referred
to in the paper showed rather clearly the difference between the insulation of a
positive and a negative wire, brought about by electric endosmose. The switch
affected was the negative one, and a good deal of electrolysis had taken place
on it. The positive switch, although placed only a short distance away in an
exactly similar position, was absolutely unaffected, and the leak which had
caused the formation of alkali on the negative one had taken a very roundabout
way, and not the short, direct path between the two switches, as might have
been expected.
1 J. Russ. Phys. Chem. Soc. (1901), 33, 588; Zeits. anorg. Chem. (1902),
30,109.
2 See The Electrician, 34, 308 (1895).
3 In this connection see an interesting paper, by F. Fernie, In The Electrician, 57,
125 (1906). Several of the statements in the next few lines have been borrowed
from this article.
4 The Electrician, 34, 563 (1895).
|
|
|
condennnsa
Hazard to Others
Posts: 217
Registered: 20-4-2010
Location: Romania
Member Is Offline
Mood: No Mood
|
|
I found a place that sells nichrome (80% Ni, 20% Cr) heating elements real cheap, about $2 for a 2000watt element, each one is about 30 grams in
weight. I figured, could I use a bath of about 30% H2SO4 and coil say 10 of these elements together, use them as anode, and plate it on a piece of
stainless or whatever? Just like the way copper is electrorefined. That would give on heck of a nickel electrode.
|
|
|
Magpie
lab constructor
Posts: 5939
Registered: 1-11-2003
Location: USA
Member Is Offline
Mood: Chemistry: the subtle science.
|
|
Is there an unofficial conspiracy against the selling of sodium to individuals? I am finding it increasingly hard to find. It seems eBay banned it
some years ago and now one of my trusted suppliers just announced that they no longer sell it.
The single most important condition for a successful synthesis is good mixing - Nicodem
|
|
|
Polverone
Now celebrating 21 years of madness
Posts: 3186
Registered: 19-5-2002
Location: The Sunny Pacific Northwest
Member Is Offline
Mood: Waiting for spring
|
|
I have seen members here recommend galliumsource.com. They still appear to carry sodium and sell to anyone.
PGP Key and corresponding e-mail address
|
|
|
Magpie
lab constructor
Posts: 5939
Registered: 1-11-2003
Location: USA
Member Is Offline
Mood: Chemistry: the subtle science.
|
|
Thanks Polverone. Galliumsource even states that sodium is becoming increasingly hard to find. It seems that in the not-too-distant future we may
all be faced with constructing our own sodium making machines.
Someone is always wanting to start his own chemical manufacturing business in his garage. For them, making sodium may soon become a business
opportunity. It's already priced somewhere between filet mignon and truffles.
The single most important condition for a successful synthesis is good mixing - Nicodem
|
|
|
ScienceSquirrel
|
Thread Pruned
13-3-2012 at 05:14 |
ScienceSquirrel
|
Thread Pruned
13-3-2012 at 05:20 |
ScienceSquirrel
|
Thread Pruned
13-3-2012 at 05:38 |
Dave Angel
Hazard to Others
Posts: 128
Registered: 22-3-2005
Location: UK
Member Is Offline
Mood: 0 K
|
|
β-Alumina Method
Really pleased to see the success had with Castner here, and it would be great to see the other hot electrochemical sodium methods successfully
performed at a decent scale by us.
The β-alumina method is where I'll be focussing my efforts for now. If you haven't yet done so, you can download ziqquratu's
attachment from page 11; the paper makes for a good read.
To summarise, we have a liquid sodium cathode, and liquid NaAlCl4 occupies the adjoining chamber with a graphite or RVC anode. The two are
separated by a sodium-type β-alumina ceramic which selectively allows only the passage of sodium ions. Current causes said ions to flow through
the alumina to the sodium cathode, where it is reduced to more sodium.
Chlorine is produced at the anode leaving AlCl3 which regenerates NaAlCl4 with excess NaCl present.
In a patent (http://www.patentgenius.com/patent/6235183.html) a similar method is described that involves addition of excess metallic Al rather than NaCl to
the NaAlCl4 melt in order to generate AlCl3, making two useful industrial chemicals at once.
For amateur use, I propose both NaCl and Al be present in the NaAlCl4 melt, perhaps with a sacrificial Al anode instead of, or in addition
to, the loose Al. My chemistry is rusty, but would this not then result in generation of AlCl3 at the anode (or in the mix if loose Al
used) which would then regenerate the NaAlCl4? This set up would neatly minimise the need to scrub Cl2 or capture
AlCl3 from the cell.
Anything I've overlooked in the chemistry? Worst case: the chemistry doesn't work and a Cl2 scrubber is needed.
|
|
|
Dave Angel
Hazard to Others
Posts: 128
Registered: 22-3-2005
Location: UK
Member Is Offline
Mood: 0 K
|
|
I have ordered the main components for a β-alumina cell, and additionally most parts to build a small Castner cell to produce the initial sodium
required for the former cell type.
I'm proposing that, for the initial NaAlCl4, a simple HCl generator of excess NaCl with NaHSO4 is used, drying and potentially
heating the evolved HCl before passing it into a heated mixture of dry, recrystallised and powdered NaCl (from dishwasher salt) and aluminium powder
(250 mesh, filler grade).
At an elevated temperature (say >200°C - with NaAlCl4 melting at 185°C) molten AlCl3 is generated, and in situ with the
NaCl forms molten NaAlCl4.
Sound reasonable?
If successful, it should be feasible to adapt the entire method to potassium production by use of a K-type β-alumina and KCl...
|
|
|
mineralman
Hazard to Self
Posts: 64
Registered: 15-6-2012
Location: WALES UK
Member Is Offline
Mood: complicated
|
|
name of book?
| Quote: Originally posted by Organikum | NaOH sodium electrolysis is done with this:
The trick is the iron net between the electrodes (cathode - copper, anode - nickel) which are only 2cm apart. This is a very tight net (100/per cm*cm)
and yes it divides also the voltage of about 4V.
If interest I can post more data on this. |
Hi, I just started reading this thread and read the words "The original process is so old, that little of the precise method/set up details are
available" ?? roughly.
I instantly thaught back to a book that was passed down to me by my great uncle Harry Driver (Boffin @ Royal (warren) Arsenal, Woolwich Arsenal).
It had a detailed history w/pix, of all the pioneers in chemistry, from there humble beginings to the Industrialisaton of there processes/partnerships
(castner/kellner for eg), polution containment and the realisation that one factorys pollution is anothers gold. but I digress
The image you have there is almost identicle to the ones in that book. Unfortunatly the police took it when they thaught I was making meth. lol, most
days I have trouble making my mind up about something, making meth would be a nightmare.
The book in question was a green hardback,small A5ish size w/black print on cover, would that image be from a similar book? and if so, could you let
me know the ISBN or its equivalent.
It's a long shot I know, but that book ment the world to me on both, it's sentimental & educational levels. MM
|
|
|
mineralman
Hazard to Self
Posts: 64
Registered: 15-6-2012
Location: WALES UK
Member Is Offline
Mood: complicated
|
|
| Quote: Originally posted by Magpie | | Is there an unofficial conspiracy against the selling of sodium to individuals? I am finding it increasingly hard to find. It seems eBay banned it
some years ago and now one of my trusted suppliers just announced that they no longer sell it. |
f***ING TERRORISTS`N`DRUG COOKS.
The way in which they changed the drug precurser & general chemical buying laws, has turned both to becoming weekly shopping list chemists, and
slowley but surely all those items you could just buy off the shelf will be replaced with modified versions, (inhibited acids,namebrand multiple
ingrediant fertilizers instead of single chemical ingrediant & having to sign or show ID to purchase them), they should have invested more
time/money in the keeping tabs on, and allowing the sales of those original precursers & chems, they would at least have known to whom and where
they were going, now they havn't got a clue as everyone is building castner cells & mixing wood ash water to the concentrated scrapings of white
bacterial matter from there backyard shit pile 
So both good & bad, good that only the ones pepared to put the time/effort in to learning the wonders of alchemy.
Bad that something so usualy readily available takes days to weeks to make.
But as for conspiracy, that would mean this conversation never happened, as we would be unaware of anything going on. MM
|
|
|
mineralman
Hazard to Self
Posts: 64
Registered: 15-6-2012
Location: WALES UK
Member Is Offline
Mood: complicated
|
|
Any decent rock shop will have Lepidolite, but a shop that specalises in mineral specimens will have some real quality lithium content Lepidolite. MM
[Edited on 26-7-2012 by mineralman]
 
|
|
|
Dave Angel
Hazard to Others
Posts: 128
Registered: 22-3-2005
Location: UK
Member Is Offline
Mood: 0 K
|
|
Regarding mineralman's comment of chemicals becoming more difficult to aquire OTC or otherwise, we have to face the fact that, for
the most part, modern society will never understand our hobby. I've posted before about even university chemistry teachers questioning my motives, and
it was only that which surprised and disappointed me.
One way or another we learn to live with it, but then I've always considered it as much a challenge as it is an annoyance...
Anyway, I'm getting off topic.
To celebrate 10 years of science madness, I thought it would be rather appropriate to construct a Castner cell out of this:
Look familiar? I think it's quite apt 
For an off the shelf item, this product is near-perfect for the build; all cast iron, the pestle even has a screw thread for the SS palm rest which,
removed, is the perfect place for a connection to be screwed in.
So far I've sliced the grinding head off the pestle, filed the resulting rod and worked it through 6 grits (down to 600) of alumina / wet&dry
paper (used in the latter 'mode') and had it plated with >500 microns of nickel - nice and shiny:
Sure, the plating wasn't absolutely necessary but, costing surprisingly little, it was a no brainer.
I'm looking forward to a weekend working on this, the intention being to strip the paint from the mortar, put a hole in the bottom and fix the
modified pestle upright as the cathode using fire cement. How this will hold up to (near) molten NaOH is uncertain, so I have a few ideas, building on
what I've read:
a) Keep the bottom cool so that solid NaOH provides a barrier between the molten alkali and the cement.
b) Fuse some NaCl and fill a small recess above the fire cement with this to offer a protective layer that will not melt at the operating
temperatures.
Any idea as to whether molten NaOH will attack solid NaCl at ca. 300°C? I know they have a common ion but I'm concerned about exchange of the anions
resulting in erosion of the solid.
Any other suggestions for the build are, of course, welcome.
|
|
|
| Pages:
1
..
14
15
16
17
18 |
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
