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Agari
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Red Material?
I was making silicon tetrachloride using the following method:
-Added around 75 grams of crushed up TCCA pool tablets to a 3-neck flask and sealed one of the necks.
-Attached an addition funnel with a mixture of 50 milliliters of hydrochloric acid and 50 milliliters of water.
-I then connected the final neck of the flask to a test tube full of concentrated sulfuric acid using plastic tubing.
-I then connected the test tube with acid to a reaction tube with 12 grams of somewhat dry silicon powder inside.
-The reaction tube was then connected to a water-cooled condenser,which in turn was connected to another 3-neck flask placed in an ice bath,with one
end being connected to an inverted-funnel trap in hydrogen peroxide.
-I then opened up the stopcock on the addition funnel,which then caused the HCl-water mixture to enter the flask with the TCCA inside and hopefully
generate chlorine.
-I started heating the reaction tube with a blowtorch,and I could see that the silicon powder began to glow at seemingly random locations and traces
of green gas(chlorine) inside the tube.
-After some time, I started heating the top of the tube.
In the end,the vapor that came over into the condenser turned a red-ish color,with some clear liquid dripping into my collecting flask.
In the end,my final product was a collecting flask with a red liquid inside,so the question is:What is the red liquid that ended up in my collecting
flask? As far as my knowledge goes,silicon tetrachloride is colorless.
[Edited on 8-10-2015 by Agari]
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Oscilllator
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Nice Experiment Agari.
Is it possible that there were sulfur impurities in your silicon? If so, it is possible that you produced some sulfur dichloride, which is a red
volatile liquid.
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Agari
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Quote: Originally posted by Oscilllator  | Nice Experiment Agari.
Is it possible that there were sulfur impurities in your silicon? If so, it is possible that you produced some sulfur dichloride, which is a red
volatile liquid.
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If I were to compare the look of the liquid to something we can all relate to,I would say that it looks like a strawberry smoothie and is rather
opaque,and not a transparent liquid. But let's assume that it is sulfur dichloride,will vacuum filtration or sep-funneling isolate the silicon
tetrachloride?
[Edited on 9-10-2015 by Agari]
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blogfast25
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Very nice experiment indeed, Agari. Of the kind we could do with many more over here. But a picture tells a thousand words, though (in addition to
your good write up).
The red must almost by definition be caused by some impurity in your silicon, and as Oscillator said sulphur is a contender here.
Do you have any idea of the purity of your silicon powder or its provenance? It's easier to purify something if you know what the impurity
might be.
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Agari
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| Quote: Originally posted by blogfast25 | Very nice experiment indeed, Agari. Of the kind we could do with many more over here. But a picture tells a thousand words, though (in addition to
your good write up).
The red must almost by definition be caused by some impurity in your silicon, and as Oscillator said sulphur is a contender here.
Do you have any idea of the purity of your silicon powder or its provenance? It's easier to purify something if you know what the impurity
might be. |
Pic related:the collecting flask separate from the main setup,cropped out the unnecessary parts
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j_sum1
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Going out on a limb here. The sulfuric acid is to dry the chlorine, right? How likely is it that your gas picked up something at this stage?
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Agari
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| Quote: Originally posted by j_sum1 | | Going out on a limb here. The sulfuric acid is to dry the chlorine, right? How likely is it that your gas picked up something at this stage?
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Well,I would say that the most it could pick up is either water between the sulfuric acid flask and the collector or,as others are theorizing,possibly
sulfuric acid,I did not monitor the conditions within the system,obviously. When I separated the condenser from the reaction tube, a white gas came
out,probably chlorine and SiCl4.
[Edited on 9-10-2015 by Agari]
[Edited on 9-10-2015 by Agari]
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blogfast25
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Things to look out for are tubing, connectors, sealing grease or seals that might react with chlorine and contaminate your
SiCl<sub>4</sub>.
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blogfast25
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| Quote: Originally posted by j_sum1 | | Going out on a limb here. The sulfuric acid is to dry the chlorine, right? How likely is it that your gas picked up something at this stage?
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Using conc. H2SO4 to dry something like Cl<sub>2</sub> is fairly standard and should not be problematic. Cough.
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100PercentChemistry
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I can't find much. The silicon tetrachloride is not red. It could either be impurities, or a siloxane. Silicon tetrachloride reacts with water to
form those.
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blogfast25
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Siloxanes are colourless too.
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100PercentChemistry
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I can't find much. The silicon tetrachloride is not red. It could either be impurities, or a siloxane. Silicon tetrachloride reacts with water to
form those.
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Agari
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| Quote: Originally posted by 100PercentChemistry | | I can't find much. The silicon tetrachloride is not red. It could either be impurities, or a siloxane. Silicon tetrachloride reacts with water to
form those. |
In either case, what should I do to separate the silicon tetrachloride from the rest of the product? Will a simple distillation work? Do I need to
vacuum filter or use a sep-funnel?
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j_sum1
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| Quote: Originally posted by blogfast25 | | Quote: Originally posted by j_sum1 | | Going out on a limb here. The sulfuric acid is to dry the chlorine, right? How likely is it that your gas picked up something at this stage?
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Using conc. H2SO4 to dry something like Cl<sub>2</sub> is fairly standard and should not be problematic. Cough. |
I was not really questioning the procedure. More the possible issues of contaminants (source of sulfuric acid?), plastic hose, rubber bung and any
interactions these may have with either Cl2 or the acid. I was also throwing out a wild stab as to whether drying the chlorine was completely
necessary in this case. If you removed this step and the problem resolved, you would have isolated the cause. Thus far in the thread no one had
mentioned the drying stage.
Sorry for not explaining myself clearly. [offers blogfast a tissue for his cough]
[edit]
| Quote: Originally posted by 100PercentChemistry | | I can't find much. The silicon tetrachloride is not red. It could either be impurities, or a siloxane. Silicon tetrachloride reacts with water to
form those. |
And there is the answer on why it is necessary to dry the chlorine. Ignorance fought.
[Edited on 9-10-2015 by j_sum1]
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Oscilllator
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The fact that your product is cloudy means that the impurities are solid (barring emulsion silliness). Since silicon tetrachloride has a very low
boiling point, I would suggest gently re-distilling it. This has a very good chance of removing the red contaminant, and you can then easily conduct
tests on it to determine its nature.
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blogfast25
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| Quote: Originally posted by Agari | | Quote: Originally posted by 100PercentChemistry | | I can't find much. The silicon tetrachloride is not red. It could either be impurities, or a siloxane. Silicon tetrachloride reacts with water to
form those. |
In either case, what should I do to separate the silicon tetrachloride from the rest of the product? Will a simple distillation work? Do I need to
vacuum filter or use a sep-funnel? |
Distillation would probably work, since as much of the impurity is present as a solid but as you know SiCl<sub>4</sub> is very
sensitive to water, so you need to use quite dry equipment.
I do think we should continue to try and find the root cause of the contamination. That makes good science.
[Edited on 9-10-2015 by blogfast25]
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100PercentChemistry
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I can't find much. The silicon tetrachloride is not red. It could either be impurities, or a siloxane. Silicon tetrachloride reacts with water to
form those.
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Agari
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| Quote: Originally posted by blogfast25 | | Quote: Originally posted by Agari | | Quote: Originally posted by 100PercentChemistry | | I can't find much. The silicon tetrachloride is not red. It could either be impurities, or a siloxane. Silicon tetrachloride reacts with water to
form those. |
In either case, what should I do to separate the silicon tetrachloride from the rest of the product? Will a simple distillation work? Do I need to
vacuum filter or use a sep-funnel? |
Distillation would probably work, since as much of the impurity is present as a solid but as you know SiCl<sub>4</sub> is very
sensitive to water, so you need to use quite dry equipment.
I do think we should continue to try and find the root cause of the contamination. That makes good science.
[Edited on 9-10-2015 by blogfast25] |
The concentration of the sulfuric acid is around 85%(rough estimate) and approximately 35% for hydrochloric,but I can't think of much that could
contaminate the result. I should note that I saw a white gas inside the reaction tube at the beginning of the experiment,and I know that Chlorine is
yellow-green,but i think the white is either sulfuric acid or water vapor,so I will accept that it could be sulfur dichloride.
[Edited on 9-10-2015 by Agari]
[Edited on 9-10-2015 by Agari]
[Edited on 9-10-2015 by Agari]
[Edited on 9-10-2015 by Agari]
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blogfast25
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| Quote: Originally posted by j_sum1 |
And there is the answer on why it is necessary to dry the chlorine. Ignorance fought.
[Edited on 9-10-2015 by j_sum1] |
Yes, it would be folly to try such direct chlorination reactions with moist chlorine.
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100PercentChemistry
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I found the video form of your method. I am still looking... https://m.youtube.com/watch?v=wU77anzCzxg
It's probably sulfur dichloride. Most siloxanes are colorless.
[Edited on 9-10-2015 by 100PercentChemistry]
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Agari
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I actually did the experiment based on Nile's video,I thought SiCl4 might be a useful reagent,though altered the quantities and possibly
concentrations,still got red liquid.Yes yes,I know that I am a "scrub" for following it word-for-word.
Any future way to prevent contamination? I am planning on using the method in the video to make some more tetrachloride,and apparently all I had to do
was filter it with cotton.
While we are on this thread,what could SiCl4 be used for as a reagent to synthesize something that can reasonably be made at home?
[Edited on 9-10-2015 by Agari]
[Edited on 9-10-2015 by Agari]
[Edited on 9-10-2015 by Agari]
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100PercentChemistry
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Removing the red
Nile red's video says "I'm not sure what the red stuff is, but it's in a suspension, so it can be filtered away".
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Agari
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Well,since I already got the red as my final product,I would want to isolate it as well and probably store it if possible. Yeah,seems like I had to
use cotton,just watched the very end.
Now that the problem is sovled,maybe one of us should drop a comment on Nile's video,even though he is unlikely to see it.
Is the chlorine generated from TCCA according to this equation: 3HCl + C3Cl3N3O3 = 3CNOH + 3Cl2?
Where the byproducts are chlorine and cyanic acid?
[Edited on 9-10-2015 by Agari]
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blogfast25
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In the case of 'Nile Red's' video the red contamination is almost 100 % due to reaction of chlorine or SiCl<sub>4</sub> with the sealant
at the entry and/or exit of the reaction tube. Using rubber/plastic at these points, especially the exit, is really asking for trouble: use glass or
teflon joints there.
Nile Red' would also have done better to start heating at the left hand side of the Si, then gradually move heat (burner) to the right, to get much
higher yield. Doing so would exploit the considerable heat of reaction to heat the silicon to the right of the reaction front. Despite those flaws
it's a nice experiment.
[Edited on 9-10-2015 by blogfast25]
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Agari
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| Quote: Originally posted by blogfast25 | In the case of 'Nile Red's' video the red contamination is almost 100 % due to reaction of chlorine or SiCl<sub>4</sub> with the sealant
at the entry and/or exit of the reaction tube. Using rubber/plastic at these points, especially the exit, is really asking for trouble: use glass or
teflon joints there.
Nile Red' would also have done better to start heating at the left hand side of the Si, then gradually move heat (burner) to the right, to get much
higher yield. Doing so would exploit the considerable heat of reaction to heat the silicon to the right of the reaction front. Despite those flaws
it's a nice experiment.
[Edited on 9-10-2015 by blogfast25] |
Well,we should drop a comment on his video lol.
Is the chlorine generated from TCCA according to this equation: 3HCl + C3Cl3N3O3 = 3CNOH + 3Cl2?
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