Sciencemadness Discussion Board - The Short Questions Thread (4)

Does anyone routinely pyrolyse NaHSO4 to produce SO3? I am considering alternate routes to concentrated H2SO4. I do have some in stock and I have a good supplier. It is just that it is expensive whereas bisulfate is dirt cheap where I live.

I know the theory but with something like SO3 I would love advice from experience.

No experience on this experiment, but you may think about heating a mix of NaHSO4 with Fe powder in glass covered bowl in an old, disposable, microwave oven with short power burst only. Reference suggests the need for more equipment, see https://www.researchgate.net/publication/250012947_Microwave... also https://www.mri.psu.edu/sites/default/files/file_attach/135.... and more generally, http://aip.scitation.org/doi/abs/10.1063/1.2159078?journalCo... .

Needless to say, procedure can be extremely dangerous especially to eyes, lungs,...

[Edited on 31-1-2018 by AJKOER]

DraconicAcid - 31-1-2018 at 12:29

Quote: Originally posted by AJKOER

That might successfully heat the material, but you don't think that really hot sodium hydrogen sulphate will react with hot iron? That's probably the most dangerous (and least likely to work) suggestion I've seen on science madness lately.

How accurate should a barometer be ?

Sulaiman - 1-2-2018 at 03:45

I intend to re-configure my U-tube barometer to increase accuracy and durability.
I think that I understand the sources and remedies for most sources of error, it will be a matter of
How accurate does my barometer need to be for chemistry?
I realise that it is like 'how long is a piece of string ?'
so I would like to ask of anyone who has often used a barometer for chemistry in the 0 -1 atm range;

What is the most precision that has been required of a barometer ?
and Why ?

Thanks in advance

P.S. I ordered an EC Class 1 stainless steel ruler for the upgrade (+/- 0.1 mm/m error)(+/- 0.1 mm end error) that arrived Saturday ... bent in two places :mad:

[Edited on 1-2-2018 by Sulaiman]

DrP - 1-2-2018 at 03:57

I intend to re-configure my U-tube barometer to increase accuracy and durability.
I think that I understand the sources and remedies for most sources of error, it will be a matter of
How accurate does my barometer need to be for chemistry?
I realise that it is like 'how long is a piece of string ?'
so I would like to ask of anyone who has often used a barometer for chemistry in the 0 -1 atm range;

What is the most precision that has been required of a barometer ?
and Why ?

Thanks in advance

What are you using it for? Only time I really needed to measure pressure accurately was doing a reduced pressure distillation. I am not sure it needed to be that accurate for that anyway.

Sulaiman - 1-2-2018 at 05:02

Reduced pressure distillation is the main intended (and assumed) use.

I currently have three unregulated operating pressures;
c760 mmHg (atmosphere), c160 mmHg (mini-piston-pump) and <1mmHg (dual stage oil rotary).
I expect that ultimately I will need a way to measure <<1 mmHg but for now I want to do reduced pressure distillation of kerosene, and because I can, ethanol from sugar.
One of the few tools available to me for the identification of fractions is b.p. which is pressure dependant.
e.g. Suppose I have a fraction of kerosene with bp 200^oC at 760 mmHg.
At 10 mmHg b.p. = 76.5^oC
If the pressure was actually 9 mmHg then 76.5^oC would imply b.p. 202.6^oC @ 760 mmHg,
or if the pressure was actually 11 mmHg the bp at 760 mmHg would be 198.5^oC
So a +/- 1 mmHg error at 10 mmHg leads to a +/-1.5^oC error in bp at 760 mmHg.
This is almost acceptable for now, so my minimum acceptable accuracy will be +/- 0.5 mm in this specific case,
but what is a reasonable level of accuracy to aim for ?

I used this tool for the calculations https://www.sigmaaldrich.com/chemistry/solvents/learning-cen...

DrP - 1-2-2018 at 06:02

Reduced pressure distillation is the main intended (and assumed) use.

I used this tool for the calculations https://www.sigmaaldrich.com/chemistry/solvents/learning-cen...

I used to use the same chart from the back of the Sigma or Aldrich catalogues. :-)

Good luck with it - sorry I can't actually be of any help. I do not know how to measure it more accurately or if it needs it... So sorry for butting in, lol. I would say that if what you are doing is working then maybe it doesn't need to be so accurate... I would try to err on the side of being slightly below the desired pressure rather than over it and then the distillation should be easy.... but I think that you would probably have a lot more experience than I in doing what you are doing.:-) Good luck.

Sulaiman - 1-2-2018 at 09:57

Quote: Originally posted by DrP

.... but I think that you would probably have a lot more experience than I in doing what you are doing.:-) Good luck.

If only !
I'm afraid I have read much more than I have done.

yobbo II - 3-2-2018 at 12:37

I have a small quantity of nickle chloride with a much larger quantity of barium chloride dissolved in water.
There is a very slight green colour. How can I ppt the nickle? Reading up on solubilities i see that the hydroxide of barium is fairly soluble and nickel hydroxide is described as not soluble. Will adding some ammonia, filtering and then boiling to get rid of excess amonia do the triick.

Yob

DraconicAcid - 3-2-2018 at 13:03

Quote: Originally posted by yobbo II

I have a small quantity of nickle chloride with a much larger quantity of barium chloride dissolved in water.
There is a very slight green colour. How can I ppt the nickle? Reading up on solubilities i see that the hydroxide of barium is fairly soluble and nickel hydroxide is described as not soluble. Will adding some ammonia, filtering and then boiling to get rid of excess amonia do the triick.

Yob

No, because ammonia will complex with nickel. You'd be better off precipitating the barium as the sulphate.

ninhydric1 - 3-2-2018 at 17:35

I've recently obtained a small amount of Ir powder for close to spot price, which is suspicious. Is there a quick and easy way to determine if it's truly iridium?

DraconicAcid - 3-2-2018 at 18:42

I've recently obtained a small amount of Ir powder for close to spot price, which is suspicious. Is there a quick and easy way to determine if it's truly iridium?

I seem to recall that iridium *won't* dissolve in aqua regia, so that's one way to test.....

ninhydric1 - 5-2-2018 at 19:21

I don't have access to the MSDS for Theochem Sulfuric Acid Drain Opener; it requires me to get an account which I detest. Anyone have a copy of it?

TheNerdyFarmer - 14-2-2018 at 04:51

Hello, so this is something that I have been thinking of for some time. If you plate a noble metal such as platinum onto a glass surface, will it make that surface inert to glass incompatible chemicals? I would of course have to fuse the coating to the glass.
I would trry it myself, but seeing as my platinum supply is so little and precious, same with nitric acid, I would like some feedback on if it could work or not. If someone here thinks that it may work, I will probably try it as soon as I make more nitric acid.

JJay - 14-2-2018 at 16:34

I don't have access to the MSDS for Theochem Sulfuric Acid Drain Opener; it requires me to get an account which I detest. Anyone have a copy of it?

Here you go. I usually use Mailinator for throwaway email addresses, along with an obviously fake name like Anonymous User. By law, they can't really require you to create an account for an SDS.

Attachment: 16b8dd_e2b255ed8e9d4ef8a828fa20cf6d580b.pdf (328kB)
This file has been downloaded 445 times

Tsjerk - 15-2-2018 at 00:58

Does anyone know if there is a way to process THF into 1,4-butanediol? I searched a bit but could only find references for the reaction in the other direction.

Edit H2SO4 acid cleavage with water as nucleofil? OH- is probably not strong enough as a nucleofil is it?

[Edited on 15-2-2018 by Tsjerk]

ninhydric1 - 15-2-2018 at 16:47

Thanks, JJay. I should use a fake email for this, good idea.

greenlight - 20-2-2018 at 19:03

Does anyone know of a synthesis writeup or any synthesis details for acetamide hydrochloride? I have been looking for a while and can't find anything :mad:

Shelf life of pH buffers ?

Sulaiman - 24-2-2018 at 01:54

My eBay pH meters came with sachets of buffer powder, pH 4.0 and 6.9.
I made up buffer solutions over two years ago, stored in airtight glass bottles.
Are these old buffer solutions likely to still be accurate ?

If not, could someone recommend long lasting diy buffer solutions suitable for pH probe callibration ?
(I have read a little on pH buffers but I don't know much about long term stability)

ninhydric1 - 25-2-2018 at 21:44

https://www.ebay.com/itm/10-30g-Natural-Powdered-Cinnabar-Pi...

I feel like this isn't actual cinnabar, otherwise getting Hg easily would be too good to be true. Anyone have experience with this source?

j_sum1 - 25-2-2018 at 21:56

https://www.ebay.com/itm/10-30g-Natural-Powdered-Cinnabar-Pi...

I feel like this isn't actual cinnabar, otherwise getting Hg easily would be too good to be true. Anyone have experience with this source?

I have jad the same questions in the past. In some circles, cinnabar is a colour. I bought some cinnabar beads at one stage that looked suspiciously like plastic when they arrived. It is one of those things that is really hard to be certain of when browsing ebay.

Bert - 25-2-2018 at 22:44

Well, the Chinese traditional medicine DOES use cinnabar, they do also make talismans and pigments for painting (used to use it for TATTOOING as well- Avoid the red designs, Yankee sailors!)

I suspect that some of these Chinese guys ARE selling actual mineral sourced or synthetic cinnabar, not just some random reddish stuff.

Handmade of natural mineral-cinnabar, mixed with refined castor oil and moxa.

At the prices quoted, you could just buy a few items and see what comes in the mail...

Or buy it from westerners for more $s.

[Edited on 26-2-2018 by Bert]

Dr.Bob - 26-2-2018 at 11:12

Quote: Originally posted by Tsjerk

Does anyone know if there is a way to process THF into 1,4-butanediol? I searched a bit but could only find references for the reaction in the other direction.
Edit H2SO4 acid cleavage with water as nucleofil? OH- is probably not strong enough as a nucleofil is it?

Just add borane to it and let it sit a while. If you find an old bottle of BH3 in THF, it will likely be contaminated with 1,4-butan-diol, especailly if not stored cold. If you reflux the borane in THF, it will crack it even more. The best part is if you quench the reaction, then evaporate the THF< the diol will be the main thing left. You can always produce borane from NaBH4 and BF3 or some other lewis acid, in theory. But old borane in THF almost always contaminates your reaction with diol.

Dr.Bob - 26-2-2018 at 11:17

My eBay pH meters came with sachets of buffer powder, pH 4.0 and 6.9. I made up buffer solutions over two years ago, stored in airtight glass bottles. Are these old buffer solutions likely to still be accurate ?

If not, could someone recommend long lasting diy buffer solutions suitable for pH probe callibration ? (I have read a little on pH buffers but I don't know much about long term stability)

Most are phosphate buffers or acetates, which are quite stable. All should be stable for years, the whole idea is that even if they change in concentration slightly, the pH should stay close to the labeled pH. I have used those solutions that were years old. And the pH meter is really only good to about 0.1 units most likely, so the buffer should stay within that much.

Diachrynic - 28-2-2018 at 13:37

My next project after extracting chromium and making dichromate is a (sodium) chlorate cell.

Quick question: If I run graphite anode, titanium or stainless steel (haven't decided yet) kathode, dichromate and pH-controlled at a current density of 17 mA/cm², how much anode corrosion do I have to expect? Is 17 mA/cm² even enough to make sodium chlorate? Is the corrosion in a potassium chlorate cell lower?

Thanks in advance.

Sulaiman - 2-3-2018 at 02:35

I'm finally going to titrate my drain unblocker sulphuric acid, say 95% w/w nominal.
What is the 'best' concentration to use for titration ?

I have previously used c1M solutions for titrations but since then I have read here that more dilute solutions may be better for accuracy.

I would like an answer accurate to +/- 0.25% using 0.2% worst case measurements of weight, volume etc.
============================
Dr.Bob ... thanks for the pH buffer quick answer.

[Edited on 2-3-2018 by Sulaiman]

Induline analog?

learningChem - 2-3-2018 at 15:22

Heating a mixture of aniline, aniline-HCl and nitrobenzene yields dyestuffs of the induline family. Would replacing nitrobenzene with nitrotoluene produce some sort of analog? (I may eventually try the reaction, but was wondering about the theory)

TIA!

CharlieA - 2-3-2018 at 17:08

I seem to think that most ordinary titrations typically involve ~0.1N solutions.

clearly_not_atara - 2-3-2018 at 20:21

Is it really that hard to get Hg? I can buy mercury thermometers at Walgreens. They have a mercury warning and a clearly-visible bulb of silvery liquid so I assume they must contain it.

SWIM - 2-3-2018 at 21:17

I suspect that cinnabar might be a variety of tumeric powder in actuality.

In the description it says it's curcuma, and that you can put it under a kids pillow to make him sleep.

Might be worth a try, but I am skeptical.

wg48 - 2-3-2018 at 23:37

I have googled this question with no luck. Does carbon dioxide displace aluminate?
Meaning will carbon dioxide decompose a concentrated solution of sodium aluminate to produce sodium carbonate/bicarbonate and aluminium hydroxide?

DraconicAcid - 3-3-2018 at 12:32

I have googled this question with no luck. Does carbon dioxide displace aluminate?
Meaning will carbon dioxide decompose a concentrated solution of sodium aluminate to produce sodium carbonate/bicarbonate and aluminium hydroxide?

Yes. The Ksp for aluminum hydroxide and the Kf are practically reciprocals of each other, so the eq'm constant for the reaction of the hydroxide ion with aluminum hydroxide to give the complex ion is close to one. At eq'm, the concentration of the complex ion will be the same as unreacted hydroxide ion (so if you saturate 1 M NaOH with aluminum hydroxide, it will be about 0.5 M sodium hydroxide and 0.5 M sodium aluminate, with a pH of 13.7ish). Carbon dioxide will convert the hydroxide ion into carbonate and then to bicarbonate, lowering the pH. if it lowers the pH to 10 (close to the pH of a bicarbonate/carbonate buffer), the hydroxide concentration will be 0.0001 M, and so will the aluminate concentration.

wg48 - 3-3-2018 at 22:23

Quote: Originally posted by DraconicAcid

Thanks for the reply.

What is the Kf constant? I assume it not the freezing point depression constant.

So is this correct: if I attempt to dissolve NaAlO4 in water, half of the Al will be deposited as the hydroxide? Does that also mean that if I attempt to dissolve excess Al in a NaOH solution it will eventually deposit Al(OH)3?

clearly_not_atara - 3-3-2018 at 22:29

Kf = formation constant, i.e. the equilibrium Al(OH)3 + OH- >><< Al(OH)4- or somesuch. Actually I'm not sure what the formation reaction is defined as in this case.

DraconicAcid - 3-3-2018 at 22:53

Kf is the eq'm constant for Al(3+) + 4 OH(-) = Al(OH)4(-)

The reaction Al(OH)3 + OH(-) = Al(OH)4(-) will have an eq'm constant of about 1, so the concentrations of hydroxide and the complex ion will be equal at equilibrium (assuming you've added enough aluminum hydroxide to saturate the solution). If you dissolve pure NaAl(OH)4 in water, you will need to add an equal amount of NaOH to prevent the precipitation of Al(OH)3.

Σldritch - 13-3-2018 at 08:22

Does anyone have solubility data for Sulfamic acid and/or various Sulfamates?

Edit: Thanks a lot Walruslover

[Edited on 13-3-2018 by Σldritch]

walruslover69 - 13-3-2018 at 08:26

Quote: Originally posted by Σldritch

Does anyone have solubility data for Sulfamic acid and/or various Sulfamates?

Sulfamic acid
12.8 wt% in water at 0 deg C; 17.57 wt% in water at 20 deg C; 22.77 wt% in water at 40 deg C; 0.1667 wt% in formamide at 25 deg C; 0.0412 wt% in methanol at 25 deg C; 0.0167 wt% in ethanol (2% benzene) at 25 deg C; 0.0040 wt% in acetone at 25 deg C; 0.0001 wt% in ether at 25 deg C
Kirk-Othmer Encyclopedia of Chemical Technology. 3rd ed., Volumes 1-26. New York, NY: John Wiley and Sons, 1978-1984., p. V21 950

[Edited on 13-3-2018 by walruslover69]

Question

CobaltChloride - 15-3-2018 at 07:17

I know that highly alkaline solutions damage glass frits from vacuum filtration systems. What is the maximum pH a solution can have without noticeably damaging the frit?

[Edited on 15-3-2018 by CobaltChloride]

Lead acetate turns cloudy when added to water - but not when making lead acetate

RogueRose - 18-3-2018 at 04:54

So when I've made lead acetate I get a crystal clear solution and when I reduce it it stays clear even at super saturation point - it may get a slight bit yellowish, only the slightest but I would consider it clear.

If I add some of the dried lead acetate to water I get a cloudy/milk solution. When drying the compound then I remove all of it from the evaporation dish, then add water to clean or get the rest of the remaining compound off the dish, it is milky white - not opaque but cloudy white.

I've thought maybe this is lead carbonate but if that is the case, would lead acetate turn to lead carbonate if it were left to sit out? Where does the acetate go if it is replaced with CO2? This doesn't seem like a balanced equation and IDK what is happening here.

Answer

CobaltChloride - 18-3-2018 at 08:03

Quote: Originally posted by RogueRose

So when I've made lead acetate I get a crystal clear solution and when I reduce it it stays clear even at super saturation point - it may get a slight bit yellowish, only the slightest but I would consider it clear.

If I add some of the dried lead acetate to water I get a cloudy/milk solution. When drying the compound then I remove all of it from the evaporation dish, then add water to clean or get the rest of the remaining compound off the dish, it is milky white - not opaque but cloudy white.

I've thought maybe this is lead carbonate but if that is the case, would lead acetate turn to lead carbonate if it were left to sit out? Where does the acetate go if it is replaced with CO2? This doesn't seem like a balanced equation and IDK what is happening here.

It may be that your water has some chloride or sulfate and forms insoluble salts with Pb II. I know that some brands of distilled water have enough chloride to make a cloudy solution when mixed with silver nitrate (from a NileRed video on the silver mirror).

S.C. Wack - 18-3-2018 at 08:16

Everything that forms an insoluble carbonate does this?

wg48 - 26-3-2018 at 04:59

I ordered 10g. It arrived today. The first thing I noticed is the powder is low density not like mercury oxide. It is not soluble in water. On heating about 100mg in an open test tube to a dull red temperature. The powder turned black and slight red condensation formed in the cooler part of the tube with a thin dark red liquid line towards the heated portion of the tube. No sign of any mercury condensation.

I conclude the powder is not mercury sulphide

ninhydric1 - 26-3-2018 at 06:21

Well, that's a few dollars wasted on my part. Thanks anyway, wg48, for the information.

CobaltChloride - 26-3-2018 at 08:47

Quote: Originally posted by CobaltChloride

I know that highly alkaline solutions damage glass frits from vacuum filtration systems. What is the maximum pH a solution can have without noticeably damaging the frit?

[Edited on 15-3-2018 by CobaltChloride]

Since nobody answered, I did some research. I found an article which says that porous glass is damaged by solutions with a pH >9.

wg48 - 26-3-2018 at 09:14

Well, that's a few dollars wasted on my part. Thanks anyway, wg48, for the information.

The item I purchased from Ebay was posted under this heading "Rocks, Fossils & Minerals > Mineral Specimens"

and described as "Natural Powdered Cinnabar Pigment"

I think I can reasonable claim it is not as described unless anyone knows a red mineral that turns black when heated and is slightly volatile. So I should get my £1.49 back from Ebay or PayPal. If you purchased the same item you should get your money back too.

Volitox Ignis - 26-3-2018 at 17:05

Are alkyl halides acidic? If so, how strong?

OldNubbins - 26-3-2018 at 17:38

and described as "Natural Powdered Cinnabar Pigment"

I think I can reasonable claim it is not as described unless anyone knows a red mineral that turns black when heated and is slightly volatile. So I should get my £1.49 back from Ebay or PayPal. If you purchased the same item you should get your money back too.

They also mention 'Curcuma' at the start of the description. Does it smell like tumeric?

DraconicAcid - 26-3-2018 at 19:25

Are alkyl halides acidic? If so, how strong?

No, not in the Bronsted-Lowry sense. The can act as Lewis acids and be attacked by nucleophiles, but they can't really be deprotonated.

clearly_not_atara - 26-3-2018 at 22:59

Another member had asked me by PM what is the best method to cleave an alkene in the presence of a benzylic methyl (thus without permanganate), if the acid is acceptable. There are two methods I think are good: iodobenzenes/Oxone and tungstic acid/hydrogen peroxide.

Iodobenzenes/Oxone
These methods work by generation of an iodonium ion that cleaves glycols while being reduced to the iodobenzene, basically a recyclable periodate. Various catalysts are used, including iodobenzene itself; iodomesitylene, which is quite good, may be available for purchase. I think the easily-produced 3-iodobenzoic acid will suffice for most purposes, since you still generally save quite a bit of iodine vs. a periodate method:
Attachment: iodobenzoic_acid.pdf (242kB)
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A rough description of the method, using 4-iodobenzoic acid or iodobenzene in acetonitrile/water, is given here:
Attachment: iodoxy_olefinox.pdf (179kB)
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Since Oxone is responsible for glycol formation and iodobenzene is responsible for cleavage, I think that it might improve yields or lower catalyst loading if you react the alkene with 1.1 equivalents Oxone for a few hours before adding the iodobenzene and remainder of the Oxone. Oddly none of the papers I've read has actually tried this, though they all report the same mechanism I just described.

Oxidation with tungstic acid/hydrogen peroxide
A Japanese paper in 1989 reported that tungstic acid / hydrogen peroxide cleaves alkenes in refluxing tert-butanol. The only practical obstacle to this method is obtaining tert-butanol, but I don't see why any solvent that dissolves the reactants wouldn't work. Acetonitrile/water in particular seems like a reasonable bet. The reaction is sensitive to ambient acidity and works best in the range pH 4-5:
Attachment: tungstic_olefinox.pdf (320kB)
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Tungstic acid may be produced by dissolving tungsten in hydrogen peroxide, so the only thing you really need is tungsten... preferably in small pieces, as the reaction is quite slow.

Oxidations with ruthenium or vanadium reagents are also effective for this transformation but are less OTC. N-hydroxyphthalimide catalyses a novel photo-aerobic oxidation of certain highly activated alkenes, but not most of them. Periodate/osmate is a classic.

wg48 - 27-3-2018 at 01:38

Quote: Originally posted by OldNubbins

They also mention 'Curcuma' at the start of the description. Does it smell like tumeric?

No. The only smell from the open small plastic bag of the bright red powder that I could detect was a very weak smell I associate with plastic bags.

I also checked the smell and colour of some ground turmeric I have as a comparison. That has the earthy smell I associate with that spice and the colour is very different and much less intense which I would describe as an orangey beige.

Volitox Ignis - 27-3-2018 at 14:56

Does a Grignard reagent have to be alkylmagnesium halide or can it be vinyl or alkyne-magnesium halide as well?

DraconicAcid - 27-3-2018 at 15:09

Does a Grignard reagent have to be alkylmagnesium halide or can it be vinyl or alkyne-magnesium halide as well?

Vinyl will probably work. Allyl and aryl ones definitely do. Alkynylmagnesium halides would not be make by the reaction of a 1-haloalkyne with magnesium, but by the reaction of a 1-alkyne with another Grignard (acid-base metathesis).

Volitox Ignis - 27-3-2018 at 15:42

Quote: Originally posted by DraconicAcid

Does a Grignard reagent have to be alkylmagnesium halide or can it be vinyl or alkyne-magnesium halide as well?

In the case of acetylene, will that produce Ethynyldimagnesium dihalide (C₂Mg₂X₂) or just ethynylmagnesium halide
(C₂HMgX), or both?

[Edited on 27-3-2018 by Volitox Ignis]

DraconicAcid - 27-3-2018 at 15:46

Depends on whether or not you use an excess of acetylene.

How to determine sodium percarbonate purity ?

Sulaiman - 28-3-2018 at 03:35

I just received 2 kg Sodium Percarbonate, for laundry and chemistry.
https://www.ebay.co.uk/itm/SODIUM-PERCARBONATE-OXYGEN-BLEACH...

Assuming that it is mostly sodium percarbonate,
possibly with excess sodium carbonate and 'coated' (with what I do not know yet)

I would like to know what is the actual H₂O₂ content w/w.
I'd like a quick and easy method for now,
and maybe a procedure for precise determination later.

So, what is an easy method of determining the H₂O₂ content of 2Na₂CO₃.3H₂O₂ + 'other' ?

At the moment all I can think of is titration vs. dextrose with methylene blue indicator.

[Edited on 28-3-2018 by Sulaiman]

j_sum1 - 28-3-2018 at 03:41

My first approach would be to do an iodometric titration.
I don't know for sure if that will get you the information you need. But knowing how much oxidative power you have per gram is not a bad thing to know.

Sulaiman - 28-3-2018 at 04:37

My first approach would be to do an iodometric titration.

I thought that the sodium carbonate would react with iodine to form iodide and/or iodate ?

Would MnO₂ decomposition of H₂O₂ be interfered with by the sodium carbonate ?

j_sum1 - 28-3-2018 at 05:17

My first approach would be to do an iodometric titration.

I thought that the sodium carbonate would react with iodine to form iodide and/or iodate ?

And the H2O2 reacts iodide to iodine.
Good point -- there's going to be a couple of equilibria in action here and it might not play nice.

You might try a thermal decomposition and see how much CO2 and H2O2 is given off...
I am just thinking out loud here. There are likely problems with that too and not just the high temperature required.

Volitox Ignis - 6-4-2018 at 18:22

How can I determine whether a sample contains 1,2,3 trichloropropane?
How can I properly dispose of it?
What are the symptoms of exposure to it?

[Edited on 7-4-2018 by Volitox Ignis]

Diachrynic - 7-4-2018 at 08:44

How can I determine whether a sample contains 1,2,3 trichloropropane?
How can I properly dispose of it?
What are the symptoms of exposure to it?

I can only answer the last question by citing wiki:

Quote:

Humans can be exposed to TCP by inhaling its fumes or through skin contact and ingestion. TCP is recognized in California as a human carcinogen, and extensive animal studies have shown that it causes cancer. Short term exposure to TCP can cause throat and eye irritation and can affect muscle coordination and concentration. Long term exposure can affect body weight and kidney function.

Answering my own question :)

Sulaiman - 9-4-2018 at 13:13

So, what is an easy method of determining the H₂O₂ content of 2Na₂CO₃.3H₂O₂ + 'other' ?

I just decomposed sodium percarbonate in solution using MnO₂
(cleaned MnO₂ with carbon from a lantern battery)
The O₂ yield was 106%

As it was a quick small scale test setup with no calibration
I can live with the result and consider it as 100% sodium percarbonate.

Sorry to answer my own question but as a cheap source of H₂O₂ I thought others may like to know that
at least one sample of eBay sodium percarbonate is 100% (approx.)
----------------------------------------------------------------------------
I ignored the possibility of the carbon being oxidised as the molar volume of CO₂ would be the same as any used O₂.

aga - 9-4-2018 at 13:30

Could you please elaborate on what you did to find the concentration ?

Sounds like Chemistry to me !

more thought process than the actual trivial chemistry

Sulaiman - 10-4-2018 at 02:54

A little research quickly identified the most likely contaminant/diluent in commercial sodium percarbonate to be sodium carbonate,
so a simple acid:base titration may give confusing results.

As I have a jar of MnO₂ (mixed with Carbon powder) from a previous 6v lantern battery dissection,
using that seemed a simple choice.
Decompose the hydrogen peroxide - measure the volume of gas produced.

As above, I decided that if carbon would interfere in some way
then it would probably be by reducing/consuming some of the oxygen produced,
but as each mole of O₂ consumed would produce one mole of CO₂,
the gas volume produced should be the same - carry on but keep in mind.
I ignored CO₂ solubility.

As I only wanted to know the available peroxide content for use in future experiments,
which are not likely to be precisely stoichiometric, I did not intend to try for precision.

The only bit of chemistry is;
2Na₂CO₃.3H₂O₂_(s) => 2Na₂CO_3(aq) + 3H₂O_2(aq)

2H₂O_2(aq) => 2H₂O + O₂

So 1 mole of 2Na₂CO₃.3H₂O₂ produces 1.5 moles of O₂

314g of sodium percarbonate to produce 33.6 litres of gas. (1 atm. 0^oC)

For a quick test, I chose bubbling gas into an inverted measuring cylinder to measure gas volume,
my largest is 100ml,
so scaling down gives 0.9345g for 100ml gas at STP.
I decided to ignore STP compensation as my shed is still near STP

About 0.9g should be OK.

Procedure
Tare a 250ml Erlenmeyer flask with side arm and add approximately 0.9g sodium percarbonate, record actual weight added as M₁ (g).
Add c100ml warm water to dissolve the sodium percarbonate.
Fit a rubber tube to the side arm and put the other end of the tube in an inverted 100ml graduated cylinder filled with water, which is clamped above a 1l beaker with c500ml water.
Add catalyst and quickly stopper the flask.
(Catalyst = cleaned mixture of MnO₂ and carbon powder from lantern battery, less is required I guess if pure MnO₂ is used)
The equipment setup should look something like this edited plagarised drawing

When the bubbling rate subsides, swirl the flask to ensure completion of peroxide decomposition.
When all bubbling has ceased, record the volume of gas collected as V₁ (ml)

Yield = (V₁/M₁) x (314/33,600) x 100 (percent)
In my case, M₁ = 0.89, V₁ = 101
Actual yield = (101/0.89)x(314/33,600)x100 = 106%

Notes;
. as my lab is at 197m above sea level and was slightly warmer than 0^oC, the extra 6% is easily accounted for.
. the scales used were 300g x 0.01g resolution, reliable to +/- 20mg when stable and calibrated, so a source of up to 2% error.
. to fill an inverted cylinder the tube can be inserted up to the top of the inverted cylinder and remove the air by suction.
(I knew that my tubing was clean so I just sucked the air out using my mouth, it would be wiser to use an air pump)
. I recorded 101ml using a 100ml cylinder ... the extra '1' is estimated.

woelen - 10-4-2018 at 03:23

Nice piece of work. This is the kind of practical chemistry I like.
I will test my own sample of sodium percarbonate in this way.

The compound is not a true percarbonate, it actually is a normal carbonate, with hydrogen peroxide in the crystal lattice. We all know water of crystallization. Here you have a compound with hydrogen peroxide of crystallization instead of water of crystallization.

True percabonates also exist, they contain the CO4(2-) ion, which has a resonance structure of a central C-atom with three oxygens attached, where one of the three oxygens has another oxygen attached. Two of these O atoms have appr. 1.5 bond with the C atom, the one with the fourth O-atom attached has a single bond with the C atom. True percarbonates, however, are not easily obtainable.

Σldritch - 14-4-2018 at 07:03

Does Nickel (II) Chloride Hexahydrate hydrolyse upon heating? Can i just heat it to get the anhydrous salt?

Sulaiman - 16-4-2018 at 21:41

To test my diethyl ether for peroxide I intend making KI/starch papers,
to verify a negative result I need to check the papers with some other oxidizer.
A quick google did not reveal the ionisation potential of diethyl ether peroxide,
so

Someone please suggest an oxidiser to test diy KI/starch papers that is less oxidising than diethyl ether peroxide ?

TheMrbunGee - 17-4-2018 at 01:28

Quote: Originally posted by Σldritch

Does Nickel (II) Chloride Hexahydrate hydrolyse upon heating? Can i just heat it to get the anhydrous salt?

From wiki:

Heating the hexahydrate in the range 66-133 °C gives the yellowish dihydrate, NiCl₂ · 2 H₂O.
The hydrates convert to the anhydrous form upon heating in thionyl chloride or by heating under a stream of HCl gas.
Simply heating the hydrates does not afford the anhydrous dichloride.

NiCl₂ · 6 H2O + 6 SOCl₂ -> NiCl₂+ 6 SO₂+ 12 HCl

The dehydration is accompanied by a color change from green to yellow.

To test my diethyl ether for peroxide I intend making KI/starch papers,
to verify a negative result I need to check the papers with some other oxidizer.
A quick google did not reveal the ionisation potential of diethyl ether peroxide,
so

Someone please suggest an oxidiser to test diy KI/starch papers that is less oxidising than diethyl ether peroxide ?

I think it would be easier to just add some reducer to your diethyl ether, and keep it there, so no peroxides could form. Also - hide it from light.

If you need the oxidizer - it is a longshot. What do you have?

[Edited on 17-4-2018 by TheMrbunGee]

DraconicAcid - 17-4-2018 at 08:47

Quote: Originally posted by TheMrbunGee

Heating the hexahydrate in the range 66-133 °C gives the yellowish dihydrate, NiCl₂ · 2 H₂O.
The hydrates convert to the anhydrous form upon heating in thionyl chloride or by heating under a stream of HCl gas.
Simply heating the hydrates does not afford the anhydrous dichloride.

Weird. I thought nickel chloride is one of the few transition metal salts that does dehydrate fairly well with just heating.

It can also be dehydrated in ethanolic suspension by heating with triethyl orthoformate.

DraconicAcid - 17-4-2018 at 08:58

I don't know about less oxidizing, but you can test them with bleach.

Sulaiman - 17-4-2018 at 16:36

I have many oxidisers that should give a positive result with KI/starch paper,
my concern is that my diy test papers react to say H₂O₂ but not any ether peroxide actually present,
because I have no idea what the redox potential of diethyl ether peroxide is.

I do not expect problems as my diethyl ether has been stored in shade in a brown bottle with little headspace, it may even contain an inhibitor.
I want to try the test more from curiosity than fear,
but I am motivated partially by safety concerns due to my inexperience.

TheMrbunGee - 17-4-2018 at 20:35

I have many oxidisers that should give a positive result with KI/starch paper,
my concern is that my diy test papers react to say H₂O₂ but not any ether peroxide actually present,
because I have no idea what the redox potential of diethyl ether peroxide is.

I do not expect problems as my diethyl ether has been stored in shade in a brown bottle with little headspace, it may even contain an inhibitor.
I want to try the test more from curiosity than fear,
but I am motivated partially by safety concerns due to my inexperience.

Maybe try some nitrates? Not really sure, just try them..

"Sugar mix" for protien shakes - milk replacement - need to figure out ingredients

RogueRose - 29-4-2018 at 12:36

I've been trying to figure out the proprietary composition of a sugar sweetener used in a protein shake I used to make at my job. It was a mix of 2 white powdered sugars that I'm 99% sure were not standard table sugars or other easily available sugars at the grocery store. We were supposed to mix the powder with water, then blend to mix. then allow to sit in fridge until it was needed to make the shake.

Making the shake was adding the protein flavoured stuff and then filling with the sugar liquid that looked like milk. These were the best tasting shakes I've ever had and all the customers agreed and it was some relatively unknown company (apex) that only supplied some gyms/fitness centers - not available at retail stores but could buy in gym and it was expensive (and they didnt' sell the sugar mix).

The odd thing is that if you made the sugar mix, allowed to sit in fridge for 7-10 days, it smelled SOOOO bad it would make you wretch. This wasn't b/c the containers were dirty or the blender, I cleaned them well, soaked in bleach (diluted w/ water) for 2 hours, then scrubbed with a scotch brite scrubby the entire thing, so it had to be almost completely clean. But I'll never forget that smell.

I think I remember the names like Maltose, I know there was a "dextrine" maybe a maltodextrine and dextrose are the two I think I remember from the packaging. I'm pretty sure it is the last two of these. I do remember when I looked up prices for these back in 2000-2004 they were VERY high compared to sucrose, like 10-20x higher. We also were chastised for using too much as we were told it was expensive and to "cut it with water"... but we didn't use to much , it just spoiled but no manager wanted to hear that or ever smell it to confirm. I hate the man sometime!!.

So even now when I research dextrose I get a link to Glucose in Wiki. I know there was something "maltoXXXX" and pretty sure it was maltodextrine. we were told we were making basically a "sweet milk" that gave instant energy. Are there any other "MaltoXX" based sugars that I could be mistaken for this one?

[Edited on 4-29-2018 by RogueRose]

DraconicAcid - 29-4-2018 at 12:43

Dextrose and glucose are the same thing. I know maltose is a separate sugar, but that's about the extent of my carbohydrate knowledge.

solo - 8-5-2018 at 21:46

I've been searching to find if the Dakin West reaction will produce a ketone from PABA...but this far i haven't found anything in the literature, perhaps i haven't posed the question correctly....any suggestions,... solo

User13579 - 8-5-2018 at 23:56

From looking at the reaction mechanism I don't think it'll work with a benzoic acid. You need a C-H adjacent to the carboxylic acid, which benzoic acids don't have. There are probably other methods, but I can't think of one using simple chemicals right now. Perhaps you can react aniline with 2 equivalents of acetyl chloride or acetic anhydride with a Lewis acid catalyst? Although aniline sometimes forms a dimer under similar conditions so I'm not sure that it would give good results.

[Edited on 9-5-2018 by User13579]

[Edited on 9-5-2018 by User13579]

[Edited on 9-5-2018 by User13579]

ninhydric1 - 10-5-2018 at 07:11

When determining R, S chirality centers, is it required to have the hydrogen pointing at you and go from largest substituent to smallest or can I point the hydrogen away and go from smallest to largest?

I haven't encountered a molecule where the first nethod is more beneficial than the second.

DraconicAcid - 10-5-2018 at 07:20