Sciencemadness Discussion Board - The Short Questions Thread (4)

The Short Questions Thread (4)

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Texium - 22-11-2016 at 20:19

Alkyl chloride are less reactive than bromides which are less reactive than iodides. Therefore, chlorides usually give worse yields than bromides and iodides.

Bromides are usually used though because they are less expensive than iodides and give generally good yields. They're also easier to make in most cases. Usually you only see iodides used for methyl and ethyl since methyl bromide and ethyl bromide are gasses while the iodides are liquid and thus much easier to handle.

Metacelsus - 22-11-2016 at 20:41

In the case of aryl halides, aryl iodides are sometimes used when preparing the desired aryl bromide is difficult due to the system being strongly activated towards electrophilic substitution. Iodine is a weaker electrophile, so in some cases iodination can selectively yield a single product, whereas trying to brominate may give polybrominated products.

[Edited on 11-23-2016 by Metacelsus]

just a stupid chem question

Db33 - 1-12-2016 at 08:34

this is probably a very dumb question but, is it possible or okay to use a flat normal hotplate/stirrer to heat up a round bottom flask thats held in place with a lab stand? Ive seen it done on youtube a few times and i always thought that it wasnt suppose to be done but in the videos it seems to work just fine.

Texium - 1-12-2016 at 08:43

Yes, that's fine. I do it all the time. Usually the most effective way is to set up the RBF a centimeter or two from the surface of the hotplate and give it a skirt of aluminum foil so that it creates a sort of heated "air bath" between the hotplate and the flask.

App for determinging energy requirements?

Bert - 1-12-2016 at 10:54

I am thinking about a (non chemistry?!) project.

Does anyone use or know of any applications (preferably free) for determining heating requirements vs. ambient air temperatures, R value of insulation, time of year and lattitude/insolation?

Trying to decide if It is worth pursuing a few small projects such as a year round greenhouse and a (solar heated?) duck pond. Total energy required over a heating season, and ballanceing construction material costs against energy costs.

Yes, it's finally looking like winter here...

drying isopropylamine

gluon47 - 3-12-2016 at 17:10

Just finished distilling a Bach of isopropylamine extracted from a glyphosate herbicide. I want to dry the isopropylamine over a desiccant. Unfortunately, the only desicant I have on hand is anhydrous calcium chloride.

I am unsure if isopropylamine reacts with calcium chloride, is this desicant likely to dry the isopropylamine without reacting with it?

Thanks in advance

CuReUS - 3-12-2016 at 21:06

Quote: Originally posted by gluon47

I am unsure if isopropylamine reacts with calcium chloride, is this desicant likely to dry the isopropylamine without reacting with it?

no, you can't use CaCl₂ for drying amines,NaOH has to be used

gluon47 - 3-12-2016 at 21:21

Thanks, I suspected It might react. I might try drying over sodium hydroxide, But doesn't the commercial stuff contain a lot of water? I would have thought this would just make the amine wetter.

Sulaiman - 3-12-2016 at 22:40

Quote: Originally posted by Bert

I am thinking about a (non chemistry?!) project.

Does anyone use or know of any applications (preferably free) for determining heating requirements vs. ambient air temperatures, R value of insulation, time of year and lattitude/insolation?

Trying to decide if It is worth pursuing a few small projects such as a year round greenhouse and a (solar heated?) duck pond. Total energy required over a heating season, and ballanceing construction material costs against energy costs.

Yes, it's finally looking like winter here...

sorry, not what you wanted but related;
. a small kerosene heater is enough for a typical greenhouse in England
. on a clear winter's night, everything radiates into -270 C black sky and nothing useful comes back,
so blocking the radiation makes a huge difference,
I use wood over, or a thick blanket under, the glass/plastic and it helps a lot.
The sun is so low in winter that most light comes sideways,
so I leave the 'heat shield' on all winter.
I also 'double-glaze' by hanging bubble-wrap inside (one or two years of uv destroys it)
and have Al foil on the North wall.
and when ventilation is not in use, ensure that there are no draughts.
these things add up to massive heat savings.

Here, for p.v. solar cell calculations, daily insolation is c 500 W.h/m² mid-winter - when you actually need it.
(summer c 5 kW.h/m²)

IF possible, using the existing wall of a heated building as one wall of your construction both scavenges heat and insulates the wall.

good luck with the solar heated duck pond - sounds quackers to me !
EDIT: duck pond afterthoughts;
. a mirror would be more efficient than a p.v. panel
. due to freezing, direct solar heating of water is risky, so bio-unfriendly liquids in heat exchangers need to be avoided.

sorry for veering of towards whimsy.

[Edited on 4-12-2016 by Sulaiman]

gluon47 - 4-12-2016 at 21:29

Ok, I went ahead and dried the isopropylamine over NaOH. The amine looks like it has taken on a slight cloudy tinge and I'm wondering If there is enough water present for some of the sodium hydroxide to dissolve.

Can I simply decant the amine off and have no NaOH contamination or Is it necessary to distill the amine after drying to remove NaOH?

[Edited on 5-12-2016 by gluon47]

Heating Mantle question

Db33 - 8-12-2016 at 14:12

Ive noticed on ebay that there are heating mantle/stirrers that go from sizes for 100ml round bottom flasks up to 250, 500, 1000, 2000ml.

My question is, if i get a heating mantle/stirrer for the 2000ml round bottom, would i also be able to use that for smaller round bottom flasks or would i have to get the exact size heating mantle for each different size flask?

Jstuyfzand - 8-12-2016 at 14:17

If you mean something like this:
http://www.ebay.com/itm/220V-2000ml-2-Litre-Lab-Electric-Hea...

Then I would guess not, it looks like the mantle is formed to fit a specific size.
I could be wrong though.

BromicAcid - 8-12-2016 at 15:24

I have, in the past used heating mantles larger than the size of the flask I was using. Except for gentle heating I would not recommend it. If you attempt to drape insulation around the flask and the mantle to hold in the heat, do not forget that air is a poor conductor of heat. In the times when I have done this I have inadvertently 'glassed' the mantle. In other words it glowed red hot and the glass wool body of it stopped being flexible and became a brittle mass.

Db33 - 8-12-2016 at 15:28

oh thats a shame, thats going to be quite expensive then getting 2 or 3 heating mantles.

Texium - 8-12-2016 at 15:41

Just get one for the size of flask you think you'll use the most and use a hot plate with "air bath" for everything else. I've gotten by just fine the last few years without a mantle at all, though I wouldn't mind having a 500 mL one.

need to know where to buy 2 basic things

Db33 - 13-12-2016 at 07:53

first i need to know, can anyone give me a link or tell me a place that sells a filter flask side-arm stopper? i need something that can be put on the end of the side-arm of a filter flask to close off that hole. Any ideas? i cant find a name or anything fo rwhat this would be called.

Also can someone link me to a site that sells a good vacuum tubing for vacuum distillation?

Texium - 13-12-2016 at 08:58

I don't understand why you would need to close off the side-arm of a filter flask. I can think of quite literally no situation where that would be necessary. Such an item does not exist.

As for tubing, you can buy it at hardware stores in bulk. Just get a kind that isn't too flimsy and it should be sufficient.

DraconicAcid - 13-12-2016 at 11:23

Quote: Originally posted by zts16

I don't understand why you would need to close off the side-arm of a filter flask. I can think of quite literally no situation where that would be necessary. Such an item does not exist.

A rubber pasteur pipette bulb will work.

Sedit - 15-12-2016 at 00:27

Can i turn an amino acid into an amide rather easily by any chance? Im looking for the best method of converting the Amine in the amino acid into an electron Withdrawing group. Any suggestions. There is Oxidation i believe to convert it to a Nitro compound but from what i understand this is finicky and Its better if i have something reversible with relative ease.

IDK Suggestions anyone.

Question

TheNerdyFarmer - 24-12-2016 at 08:40

1. Does a 24/29 joint fit in 24/40 joint?
2. Is it possible for an individual person to order chemicals from big companies like alfa aesar ect.

gdflp - 24-12-2016 at 09:32

1. Short answer: yes. Long answer: In the vast majority of cases, there won't be any issue since the joints are compatible. However, the two may not fit together when you have a male 24/40 joint and a female 24/29 joint, and there is a rapid bend or constriction near the 24/29 joint. Since a 24/40 joint is longer than a 24/29 joint, it needs some room to extend past the end of the joint, which it doesn't have if there is a constriction.

An examples is certain types of 105° vacuum takeoff adapters, which is the most common place I've heard of an issue.

2. There has been extended discussion about this topic on the forums. While there is some variation in policy between the different companies, none of them are interested in selling anything to individuals; they will tell you that flat out if you ask them. Second tier suppliers such as Carolina Biological will sell certain things to individuals(IIRC only equipment, no chems).

If you need a certain chemical from Sigma Aldrich or Alfa, try contacting Elemental Scientific. For a while, they have been running a Special Order program, where they will order a chemical from one of the big suppliers, then ship it to you for a slight fee. That's going to be your best bet at sourcing something if it truly is unavailable everywhere else.

PHILOU Zrealone - 25-12-2016 at 15:45

Quote: Originally posted by Sedit

Can i turn an amino acid into an amide rather easily by any chance? Im looking for the best method of converting the Amine in the amino acid into an electron Withdrawing group. Any suggestions. There is Oxidation i believe to convert it to a Nitro compound but from what i understand this is finicky and Its better if i have something reversible with relative ease.

IDK Suggestions anyone.

There are many ways but it is better to know what you intend to do and the initial starting molecule...otherwise answer may be too general and vague for your specific application.

To increase the EWG power of an amine, you have to reduce its basicity...

Oxydation of the amine to nitroso or nitro may help decarboxylation of the alfa carboxylic acid group (spontaneous for nitroacetic acid).
If H is available into alfa position then the nitroso can be seen as C=N-OH

If you turn your amine into amide with an organic acid anhydride or organic acid halide, it will be more EWG.

If you add formaldehyde to it also because of CH2=N- or (HOCH2)2N-.

Halogenation of amino-acids provides haloamines that may decarboxylate and on further treatment turn into ketons or nitriles...all depends onto the struture of the carbon holding the NH2 (primary, secondary, ternary)...

Nitrosation may afword diazo-carboxylic acids which display very special chemistry see diazoacetic esters from glycine esters.

[Edited on 26-12-2016 by PHILOU Zrealone]

Question

TheNerdyFarmer - 26-12-2016 at 15:22

Is there a material that is resistant to high temperatures (like 300C) and HF and H2SO4? I can only find things like fluorinated polymers and such. Can't use glass obviously and I don't know of any refractory compositions or metals that HF doesn't react with so if anyone knows of such a tough material please do tell. Thanks in advance!

Dr.Bob - 26-12-2016 at 19:42

Tantalum is great for H2SO4, even boiling hot, but it is dissolved by HF, quartz also is immune to H2SO4 and heat, but will be etched by HF. Solid Teflon might be the only thing that will handle that well, I know it handles hot H2SO4 well, as those three materials were all used by IBM years ago to hold silicon wafers to be cleaned by immersing them in to boiling sulfuric acid. That would dissolve any fingerprints, hair, dust, fingers, and any other dirt on the wafers, they came out sparkling clean. That was one of the most hazardous places in IBM.

Teflon is actually not that hard to work with or machine, so if it is strong enough, you could test it for your work, although at high temperatures, it gets softer, so it may need to be held in some other material for support.

viton O rings

j_sum1 - 28-12-2016 at 04:47

If I wanted to purchase some replacement O rings for thermometer adapters (normal 6mm diameter thermometer) what size should I get? I have now idea how these things are measured.

diddi - 28-12-2016 at 04:53

visit your local motor mechanic. they buy o ring assortments for air conditioners and general use. you can try them on so to speak and will prolly cost you a whole 50 cents

Sulaiman - 28-12-2016 at 05:35

Quote: Originally posted by j_sum1

If I wanted to purchase some replacement O rings for thermometer adapters (normal 6mm diameter thermometer) what size should I get? I have now idea how these things are measured.

size just goes by internal diameter, and thickness or outside diameter
but what about the material?
synthetic rubber, butyl rubber, viton, silicone,
and ptfe washers
all available on eBay UK for example

I have two of the cheap Chinese adapters, both have square cross-section rubber, 6mm i.d. x 11.5mm o.d. x 2mm thick,
one is black rubber and one is translucent silicone.

one or more tight-fitting o-rings on the thermometer above the cap
gives hope that my thermometer does not drop into a flask in case of seal disintegration,
but is moveable, because anything fixed is always just in the wrong place to read the scale

[Edited on 28-12-2016 by Sulaiman]

Viable way to pure acetone?

Db33 - 30-12-2016 at 13:34

This might be dumb but, at the local pharmacy they sell 100% acetone fingernail polish remover. However it says ingredients are Acetone and Denatonium Benzoate. I know the latter is there in very small amounts as a bitter deterrent so people dont ingest the stuff. Would a distillation get rid of the denatonium benzoate?

Sulaiman - 30-12-2016 at 14:24

I believe that the denatonium benzoate wil be in the region of 10 ppm, equivalent to 99.999% pure acetone.

Reagent grade acetone is not that pure.

I have read that denatonium benzoate may interfere with the precipitation of nucleic acids,
other than that I would not worry about the 0.001% impurity.

aga - 30-12-2016 at 14:31

Quote: Originally posted by Db33

Would a distillation get rid of the denatonium benzoate?

Yep.

Maybe nobody has mentioned it yet, so here goes.

Use Google with the search term like this :-

site:sciencemadness.org acetone denatonium

TFSE will have been U'd, and you'll find many posts about this particular topic.

Be careful taking this Dark path : most are old posts from the Bad Old Days when some naughty amateur chemists posted about experiments they were planning to do, did, then <i>even posted the results</i> as they were so interested in actual Chemistry.

The horror !

[Edited on 30-12-2016 by aga]

Texium - 30-12-2016 at 22:40

Generally if you have to preface a post with "this might be dumb," it doesn't need to be its own thread.

Williamson ether synthesis

gluon47 - 1-1-2017 at 00:19

I'm planning to make some tert-butyl ethyl ether via Williamson ether synthesis. Although I understand how the reaction works, I'm not exactly sure how to go about performing the reaction.

NaOH + t-BuOH <==> t-BuONa + H2O

t-BuONa + EtBr ==> NaBr + t-BuOEt

This is what I propose to do:

Add sodium hydroxide to a large excess of tert-butyl alcohol which will act as a solvent as well as a reactant. Reflux this mixture for around 30 minutes to reach the point of equilibrium between The tert-butoxide anion and tert-butyl alcohol. Add ethyl bromide through the condenser and continue to reflux for a further 2.5 hours.

Allow to cool to room temperature, then pour the mixture into a beaker containing water and mix thoroughly. The tert-butyl ethyl ether should form a layer above the later.

Wash tert-butyl ethyl ether with two more portions of water in succession. Dry the tert-butyl ether over anhydrous CaCl2 then finally distill, collecting the fraction coming over at around 69-71 C.

I'm thinking using a slight excess of NaOH to make sure all the EtBr reacts would probably be a good idea.

Any advice would be much appreciated. Does this sound like it has a good chance of working?

[Edited on 1-1-2017 by gluon47]

CuReUS - 1-1-2017 at 01:56

Quote: Originally posted by gluon47

I'm planning to make some tert-butyl ethyl ether via Williamson ether synthesis.I'm not exactly sure how to go about performing the reaction

see this - http://www.sciencedirect.com/science/article/pii/S0040402001...

micelles (Williamson ether synthesis)

Sulaiman - 1-1-2017 at 02:28

interesting, self-arranging mollecular structures that I could confuse with biological structures.

In physics entropy tends to increase
whereas in biology and chemistry, often the opposite seems to be true.
Isn't life wonderful.

Happy New Year

[Edited on 1-1-2017 by Sulaiman]

How legal is a list 1 precursor?

Geocachmaster - 1-1-2017 at 18:01

Does anyone from the US know the legality of DEA list 1 precursor chemicals? Specifically iodine, red phosphorus, and benzaldehyde, as those are the only three on the list that I can see myself working with. I've done some research but it has only confused me. I know that the sale of said chemicals is restricted but what about only possession. For example, if I made some iodine, would it's synthesis or me storing it be illegal? Druggies getting every good chemical watched/banned makes me very mad! :mad:

Any help is appreciated

[Edited on 1/2/2017 by Geocachmaster]

red phos purity check?

Db33 - 4-1-2017 at 05:34

I have some red phosphorus i bought a few months ago, i was wondering if there is a way to check the purity such as a melting point test or some other simple way.

Tsjerk - 4-1-2017 at 08:08

Quote: Originally posted by gluon47

I'm planning to make some tert-butyl ethyl ether via Williamson ether synthesis. Although I understand how the reaction works, I'm not exactly sure how to go about performing the reaction.

NaOH + t-BuOH <==> t-BuONa + H2O

t-BuONa + EtBr ==> NaBr + t-BuOEt
[Edited on 1-1-2017 by gluon47]

I think you better use KOH, as what I understand from the potassium thread gives a alkoxide that is more soluble.

Sedit - 6-1-2017 at 20:42

Quote: Originally posted by PHILOU Zrealone

Quote: Originally posted by Sedit

Cross Coupling Via 5x and up molar excess of the minor species in the Kolbe electrolysis using Acetic acid(minor) and an amino acid(major). Adding formaldahyde would indeed make it into an EWG because I considered something similar in the past but was unsure. A direct conversion of the Carboxyl group into a methyl is totally within the realms of possibility I believe.

CuReUS - 6-1-2017 at 23:20

Quote: Originally posted by PHILOU Zrealone

If you turn your amine into amide with an organic acid anhydride or organic acid halide, it will be more EWG.

Conversion of the amine to amide would be the best way.But the carbonyl group of the amide should have EWG likes triflouro.See rhodium's post - "A two-step method for the preparation of homochiral cathinones" -http://chemistry.mdma.ch/hiveboard/novel/000360879.html

Sedit - 7-1-2017 at 00:25

http://www.sciencemadness.org/talk/files.php?pid=161264&...

Seems to suggest that its going to instead methylate the amino acid as well as decompose some of the amino acid releasing methylamine or is it just late and Im reading this wrong?

JJay - 7-1-2017 at 00:46

Quote: Originally posted by Db33

I have some red phosphorus i bought a few months ago, i was wondering if there is a way to check the purity such as a melting point test or some other simple way.

I wish I had some! I think you could do an iodometric titration with starch and potassium iodate in an aqueous medium, but it would be tricky, and first you'd have to be very careful to remove any white phosphorus by refluxing in carbon disulfide.

[Edited on 7-1-2017 by JJay]

laserlisa - 11-1-2017 at 00:41

I want to dry K2CO3 for use in a phenolic alkylation reaction. Is it enough to dry it in an ordinary oven?
Which temperature and what duration is advisable to get it anhydrous?

Thanks

[Edited on 11-1-2017 by laserlisa]

Question

TheNerdyFarmer - 11-1-2017 at 19:30

Im sure this is a stupid question but I got to know. When a solution is a certain percentage (especially an acid) such as 30% HCl or 98% H2SO4. Is that percentage referring to the percent of weight or volume or some other form of measurement?

j_sum1 - 11-1-2017 at 19:41

Not a stupid question at all. It refers to weight percent. Thus a kg of 30% HCl contains 300g of hydrogen chloride molecules and 700g of water molecules.
(It does not occupy a litre since the density is not the same as the density of water. This makes conversion between weight% and moles per litre problematic since it is density-dependent and that density is itself a function of concentration.)

For anything analytical it is normal to use moles per litre (and much lower concentrations.) But the % figure is useful for most work. I have gotten into the habit of weighing my acids and other liquids rather than measuring volume since it correlates with the information on the label.

[Edited on 12-1-2017 by j_sum1]

TheNerdyFarmer - 12-1-2017 at 05:28

Thanks a bunch for the reply. It really clarified things up. I will start trying to weigh my acids and solutions rather than measuring their volume. Thanks!

fastbre4k - 12-1-2017 at 17:11

Hey,

it is possible to hydrolyse an aldoxime with HCl to yield an carboxylic acid?

Crowfjord - 12-1-2017 at 18:27

It would yield an aldehyde, which could be oxidized to a carboxylic acid.

fastbre4k - 12-1-2017 at 21:18

mhm ok, so i guess K2Cr2O7 is a suitable reagent

PHILOU Zrealone - 13-1-2017 at 12:03

Quote: Originally posted by fastbre4k

Hey,
it is possible to hydrolyse an aldoxime with HCl to yield an carboxylic acid?

And hydroxylamine hydrochloride what has some value too.

Quote: Originally posted by Crowfjord

It would yield an aldehyde, which could be oxidized to a carboxylic acid.

Quote: Originally posted by fastbre4k

mhm ok, so i guess K2Cr2O7 is a suitable reagent

Yes with an acid just like KMnO4, Ni peroxyde, ... but first isolate the aldehyd and avoid residual HCl ...otherwise dangerous Cl2 gassing!

biomechem - 15-1-2017 at 08:26

Predicting yield of Grignard reaction. How do chemists know which rxn will give better yield when there are 2 posiblle routes of it? For example in reaction as presented below.
R¹-CHO + R²MgX or R²CHO + R¹MgX
Is it possible to predict which option would be better just by taking into account ease of creating a carbcation on carbonyl atom? Or there is no simple rule, and every case should be considered separately?

Tin dioxide preparation

Ba(ClO3)2 - 15-1-2017 at 23:00

I've managed to get hold of some pewter, which is an alloy containing about 95% tin with some copper, antimony and bismuth. I was wondering how one could go about preparing tin dioxide from this.

The most obvious route is to dissolve the pewter in HCl then precipitate the tin as the carbonate, and finally heat to decompose carbonate to oxide. However, I thought of a more interesting approach that I would prefer to use:

Dissolve pewter in sodium hydroxide solution to give a solution of sodium stannate. Add a slightly less then stoichiometric amount of hydrochloric acid. This should precipitate SnO2 as the hydrated oxide "stannic acid". Heat the hydrated oxide in a crucible to get tin dioxide.

My question is, would this second method I though of be likely to work?

laserlisa - 16-1-2017 at 03:12

Quote: Originally posted by laserlisa

I want to dry K2CO3 for use in a phenolic alkylation reaction. Is it enough to dry it in an ordinary oven?
Which temperature and what duration is advisable to get it anhydrous?

Thanks

Does anybody know?

Metacelsus - 16-1-2017 at 05:27

By my experience, drying it in an oven (200 °C to constant mass) is fine. I have methylated naphthols with dry potassium carbonate and dimethyl sulfate, and it should work for phenols. Of course, be careful with strong alkylating agents.

exodia - 19-1-2017 at 17:41

hi there, I have a couple of quick questions.

I´m going to extract the silver from some xray films (I know this topic has been greatly discussed in the forum) and I have already my set up planned, but I would like to ask you what is your recommendation between the two methods that I have.
as a side note my final product wont be silver, I´m more interested in silver nitrate.

xrays + HNO3 = silver nitrate and other stuff, react it with NaOH precipitate silver oxide redissolve in HNO3 and recristalice.

the second method is the same with the added step of adding NaCl obtaining the insoluble chloride and then silver oxide and HNO3.

I prefer the first method to reduce yield loses from the added step, my question is, will it precipitate unwanted oxides or other stuff adding the NaOH straigth away?, without isolating the chloride first?

second question: I have recently received my brand new heating mantle and I´m planning to distill some acetone (mainly to remove the denatonium benzoate and stuff) can I just put the round bottom in the heating mantle? I know it´s not really sensible distilling flammable liquids with open flame for obvious reasons, but all the volatile (mostly organic solvent) distillations I have seen have been made with a hotplate and a sand bath or water bath, this may have been just for personal prefferences, but is the a risk I´m not seeing in distillation of flammable liquids straigth away from the heating mantle?

Many thanks to everyone.

[Edited on 20-1-2017 by exodia]

PHILOU Zrealone - 20-1-2017 at 04:29

Quote: Originally posted by exodia

hi there, I have a couple of quick questions.

I´m going to extract the silver from some xray films (I know this topic has been greatly discussed in the forum) and I have already my set up planned, but I would like to ask you what is your recommendation between the two methods that I have.
as a side note my final product wont be silver, I´m more interested in silver nitrate.

xrays + HNO3 = silver nitrate and other stuff, react it with NaOH precipitate silver oxide redissolve in HNO3 and recristalice.

the second method is the same with the added step of adding NaCl obtaining the insoluble chloride and then silver oxide and HNO3.

I prefer the first method to reduce yield loses from the added step, my question is, will it precipitate unwanted oxides or other stuff adding the NaOH straigth away?, without isolating the chloride first?

second question: I have recently received my brand new heating mantle and I´m planning to distill some acetone (mainly to remove the denatonium benzoate and stuff) can I just put the round bottom in the heating mantle? I know it´s not really sensible distilling flammable liquids with open flame for obvious reasons, but all the volatile (mostly organic solvent) distillations I have seen have been made with a hotplate and a sand bath or water bath, this may have been just for personal prefferences, but is the a risk I´m not seeing in distillation of flammable liquids straigth away from the heating mantle?

Many thanks to everyone.

[Edited on 20-1-2017 by exodia]

1) When using NaOH you will indeed precipitate many metals as hydroxides or oxides...thus not only Ag.
To reduce the amount of HNO3 you will use, I think you should:
a) melt-burn-calcinate the films to ashes first (this will reduce the volume and weight of starting material since most organic matter will be lost into fumes of CO2, H2O, etc.);
b) then add slight exces of HNO3 (much less required than into your proposal) and reflux.
c) filtrate and rinse filter and remaining solid with demi water; disgard the filter and solid.
d) neutralize the filtrate with Na carbonate or bicarbonate but it must remain slightly acidic.
e) concentrate the solution by evaporation to 1/4 its volume.
f) add slight excès of solid copper. Copper will displace all metals more oxydising than itself from their salts --> Gold, Platinium,...what are usually rare and of course silver. This is called cementation, the metal precipitates as crystals or dust while the copper passes into solution as blue Cu⁽²⁺⁾.
Via a kind of electric cell reaction in shortcut:
2 Ag⁽⁺⁾ + Cu_(s) --> 2 Ag_(s) + Cu⁽²⁺⁾
g) collect the metallic silver dust and react with slight exces of HNO3 and a little H2O2.

2) Denatorium is used into ethanol alcohol to give a bad bitter taste to it (and to get the taxes onto drinkable alcohol vs solvent or fuel), or to other chemicals sothat childrens don't drink it.
I'm not sure it will be found into aceton.

Heating mantle is no troubles with highly volatile and flamable liquids as long as you put the heat low (via dimmer switch) or that you lift a bit the boiling flask sothat there is air gap and no direct contact between the flask glass and the heating element --> only radiating heat.
Will take a little more time to boil, but will be safer.
The glass will be exposed to less heat and be submitted to less dillatation, so the risk of cracking is less.
The solvent and vapour will be less prone to self inflame if the heating element is not to dull red heat.

[Edited on 20-1-2017 by PHILOU Zrealone]

j_sum1 - 20-1-2017 at 21:38

This has probably been asked and answered before, but here goes.
Why is an allihn condenser the standard for soxhlet extractors? It seems to me that any condenser would do the job. But allihns seem almost universal with grahams a distant second.

Sulaiman - 21-1-2017 at 01:39

because most soxhlet kits are sold to essential essences extractors who like the alchemy/apothecary look ?

PHILOU Zrealone - 21-1-2017 at 03:17

Quote: Originally posted by j_sum1

This has probably been asked and answered before, but here goes.
Why is an allihn condenser the standard for soxhlet extractors? It seems to me that any condenser would do the job. But allihns seem almost universal with grahams a distant second.

I think for practical reasons...
Cooling size efficiency (volume/height) vs double tubular or simple tubular...the only limit is the sky ...but in a lab it is the ceiling

... and the practical working height of the operator

.
Also robustness vs tubo helicoidal.

[Edited on 21-1-2017 by PHILOU Zrealone]

j_sum1 - 21-1-2017 at 04:32

By that reasoning a Friedrich's would be the most common.

Chemiston - 21-1-2017 at 07:10

I will probably ask a relly dumb question
But seriously how do I get these stars that are below some people's title

e.g 5 stars is international hazard

where mine is just harmless

ficolas - 21-1-2017 at 08:32

Quote: Originally posted by Chemiston

I will probably ask a relly dumb question
But seriously how do I get these stars that are below some people's title

e.g 5 stars is international hazard

where mine is just harmless

Shitposting, spamming the forum, etc.
No justo kidding, but not really. They correspond to the number of posts (and make them as constructiva as posible!!! No shitposting and spam

)

PHILOU Zrealone - 21-1-2017 at 09:06

Quote: Originally posted by j_sum1

By that reasoning a Friedrich's would be the most common.

Yes for efficiency,
but
No because more fragile and expensiver (a lot of precision glassery work).

j_sum1 - 25-1-2017 at 17:33

Does anyone use this method for cleaning glassware?
https://www.youtube.com/watch?v=rJik_EnmgM0

ferrous chloride and hydrogen peroxide

I have not come across it before. Looks to be a similar idea to pirahna but perhaps more foamy and messy. And perhaps safer too.
But I am not really sure that I understand the chemistry behind it. I presume there is a bit of catalysis going on to react carbon with H2O2 and maybe some oxidation of the Fe(II).

gdflp - 25-1-2017 at 18:49

I haven't used it before personally, but the chemistry behind it is fairly well known.(At least, it's famous enough to have its own name

) [url=https://en.wikipedia.org/wiki/Fenton's_reagent]link[/url]

EDIT:Hmm, the hyperlink function of the forum doesn't seem to be working.

[Edited on 1-26-2017 by gdflp]

Question

TheNerdyFarmer - 27-1-2017 at 06:28

I was using an oil bath for a synthesis. I was using coconut oil for my oil bath. Well long story short, some of it got on my hotplate (which is ceramic top) and left a large carbon deposit on it. My basic solvents won't get it off and I don't want to scrape it and risk scratching and scraping the chemical resistant layer off the hotplate top. Is there a way to get rid of the carbon without destroying the surface of my hotplate?

Cleaning hotplate

Geocachmaster - 27-1-2017 at 14:19

Hot piranha seems to do the trick!

I personally wouldn't bother, my hotplate is covered with stains which do not interfere with its function. Thick deposits of carbon can be easily scraped off, maybe try a kitchen scrubbing pad for the residues left? Most ceramic hotplates can take a bit of abuse, but then again not all are equal.

Edit: Sharp metal tools can and will scratch the surface of the ceramic, so avoid these if the hotplate still looks nice. My Corning's ceramic is 4mm thick so it would be difficult to break through and ruin the chemical resistance.

[Edited on 1/27/2017 by Geocachmaster]

TheNerdyFarmer - 27-1-2017 at 14:48

Mine is a Corning PC-420D. How thick do they make the chemical res surface and would steel wool work okay? I'm too scared to work with hot piranha out on my lab bench lol.

[Edited on 27-1-2017 by TheNerdyFarmer]

Geocachmaster - 27-1-2017 at 15:11

I have a Corning PC-351 which has 4mm thick ceramic. I believe that the ceramic is the chemical resistant part (pretty non-reactive stuff by nature). Other Cornings probably have similar thicknesses. I tested #00 steel wool and ~10 seconds of vigorous scrubbing had no damaging effect and made no visible scratches. So #00 and finer steel wool will be good. For reference #00 has a texture of rough woolen clothing.

CharlieA - 27-1-2017 at 17:22

How about burning off the C with a Bunsen burner or Bernz-0-Matic?

TheNerdyFarmer - 28-1-2017 at 07:39

I will first try the steel wool and if that doesn't work I may try taking the torch to it to burn it off. Thanks for the replies and all the help.

[Edited on 28-1-2017 by TheNerdyFarmer]

TheNerdyFarmer - 28-1-2017 at 15:08

Also what kind of material do they use in industry
as a reaction vessel make hydrofloric acid???

[Edited on 28-1-2017 by TheNerdyFarmer]

Metacelsus - 28-1-2017 at 15:31

Nickel alloys (for example, monel) are passivated by HF and thus resist its corrosive properties.

Lithium - 28-1-2017 at 19:12

A quick question which I've not seen answered elsewhere:

During the process of recrystallising something, my aqueous solutions of the substance after filtration quite often go mouldy. This has happened to cool, saturated solutions of Magnesium sulfate, potassium chlorate and potassium chloride. I am particularly surprised that an organism can live and grow in a saturated solution of potassium chlorate.

Does this happen to anyone else? If so, what methods do you employ to prevent micro-organism growth in your chemical solutions?

Geocachmaster - 28-1-2017 at 19:59

I recently noticed some mold growth in a container of MnO₂ waste, very odd. This was only after sitting undisturbed for a couple weeks though. Do you have a history of/ongoing mold problems in your lab space?

Edit: this is the only time I have ever seen mold in my lab

[Edited on 1/29/2017 by Geocachmaster]

Lithium - 28-1-2017 at 20:15

Geocachmaster, I've never had any kind of mould issues in or on the building itself, but persistently solutions of various chemicals will go mouldy.

Evaporating a solution by leaving it sit on a windowsill is almost nonviable as mould or bacteria will develop before the solution is fully evaporated, requiring filtration, pasteurisation and recrystallisation to purify again.

JJay - 30-1-2017 at 15:39

What is the maximum temperature you can safely reach in a round-bottom flask in an air bath on a regular ceramic hot plate like the PC-351?

DraconicAcid - 30-1-2017 at 16:53

Not sure about air baths, but I've seen heating mantles get hot enough to soften the pyrex glass. About 350 C, IIRC.

Do you mean safe for the glass, or safe for the hot plate?

JJay - 30-1-2017 at 17:01

Safe for the hot plate... I have a heating mantle, but it is too large for the flask, and I've had awful luck with sand baths.

I guess maybe I'll just break out my propane burner and wire gauze....

[Edited on 31-1-2017 by JJay]

JJay - 31-1-2017 at 14:31

I think pretty much everyone on here knows by now that crystals often have water in the crystal structure. For example, the sodium carbonate you buy at the grocery store usually isn't pure sodium carbonate; it's sodium carbonate monohydrate, with one mole of water molecule per mole of sodium carbonate. Copper sulfate sold as root killer is copper sulfate pentahydrate, with five moles of water per mole of copper sulfate. If a crystalline substance contains half a mole of water per mole, it's a hemihydrate. And so on....

Substances crystallized from methanol or ethanol often have methanol or ethanol in the crystal lattice. I have never been taught or read any clear rules on how to name such crystals, though... does anyone know what to call a crystal of a substance that contains one mole of methanol per mole of substance, for example?

Question

TheNerdyFarmer - 31-1-2017 at 15:41

I made some aluminum Chloride by dissolving aluminum in HCl. Well there was a blackish brownish suspension left so I preformed a Vacuum Filtration to remove all of this. When I tried to clean out the sintered vacuum funnel it was super resistant. Couldn't even get pirranah solution to clean it out. What is this stuff and how do I clean it out?

Elemental Phosphorus - 31-1-2017 at 16:00

Maybe try HCl since it is what you originally used. Maybe use strong bleach?

PHILOU Zrealone - 31-1-2017 at 16:14

Quote: Originally posted by JJay

I think pretty much everyone on here knows by now that crystals often have water in the crystal structure. For example, the sodium carbonate you buy at the grocery store usually isn't pure sodium carbonate; it's sodium carbonate monohydrate, with one mole of water molecule per mole of sodium carbonate. Copper sulfate sold as root killer is copper sulfate pentahydrate, with five moles of water per mole of copper sulfate. If a crystalline substance contains half a mole of water per mole, it's a hemihydrate. And so on....

Substances crystallized from methanol or ethanol often have methanol or ethanol in the crystal lattice. I have never been taught or read any clear rules on how to name such crystals, though... does anyone know what to call a crystal of a substance that contains one mole of methanol per mole of substance, for example?

mono-methanol-ate

JJay - 31-1-2017 at 16:24

Quote: Originally posted by PHILOU Zrealone

mono-methanol-ate

Are you sure? That seems reasonable, but the most common use of methanolate seems to be to denote methoxide....

Edit: Nomenclature in this area is confusing, but you are correct.

[Edited on 1-2-2017 by JJay]

TheNerdyFarmer - 31-1-2017 at 16:47

Why would bleach work???

Molbase?

Geocachmaster - 31-1-2017 at 17:57

I just stumbled across a website called Molbase. They appear to be a service which specifically finds chemical suppliers. They have places in North America, India and China, but are based primarily in China. Some prices are intriguing, like this one; 1kg lidocaine for $30. I though making denatonium benzoate like NileRed would be cool, and this would be an amazing price. Even if there was way overpriced shipping it would still be amazing. Does anyone have experience with this website? Is it a legiamite thing?

Thanks

Crowfjord - 31-1-2017 at 19:32

Quote: Originally posted by TheNerdyFarmer

I made some aluminum Chloride by dissolving aluminum in HCl. Well there was a blackish brownish suspension left so I preformed a Vacuum Filtration to remove all of this. When I tried to clean out the sintered vacuum funnel it was super resistant. Couldn't even get pirranah solution to clean it out. What is this stuff and how do I clean it out?

Where did the aluminum come from? The black-brown stuff is probably silicon. Cast and rolled aluminum alloys tend to contain significant amounts of silicon from the casting process. If this is the case, I don't think that anything beside HF would dissolve it. Remember to use filter paper if you try again.

TheNerdyFarmer - 1-2-2017 at 09:51

I have an idea. If I pass chlorine gas through the funnel, shouldn't the chlorine react with the silicon to form silicon tetrachloride? please leave some input on this if you can. BTW I know that silicon tetrachloride is super dangerous but I don't have HF which is probably more dangerous.

Crowfjord - 1-2-2017 at 18:37

Chlorine might work, but I am not sure. That's a little out of my realm of expertise. By the way, hydrofluoric acid would probably be a bad choice to clean a frit anyway, since the frit would also be dissolved to some extent.

gdflp - 1-2-2017 at 20:21

Quote: Originally posted by TheNerdyFarmer

I have an idea. If I pass chlorine gas through the funnel, shouldn't the chlorine react with the silicon to form silicon tetrachloride? please leave some input on this if you can. BTW I know that silicon tetrachloride is super dangerous but I don't have HF which is probably more dangerous.

I'm not sure if that would work near room temperature, I've never seen such a reaction reported. On a more positive note, if you can't find anything to dissolve the silicon and remove it, it's likely that the only consequence to the frit will be cosmetic.

TheNerdyFarmer - 2-2-2017 at 18:13

So if I leave it like it is, it won't bother anything?

Erlenmeyer vs RBF

Geocachmaster - 3-2-2017 at 09:21

I usually use an air bath for heating RBFs because it is simple, although it suffers in efficiency. For better heating, larger quantities or high temperatures I use a water or oil bath. Twice now I have spilled the oil bath which leads to a huge mess and oil all over the bench and hotplate. I am now contemplating buying a bunch of jointed erlenmeyers. There would be more heat transfer to the flask and better stirring. For simple distillations and reflux I don't usually need more than one neck, and addition can be through the condenser if needed. Is there any reason why RBFs are so much more popular than erlenmeyers? Are they superior? Nurdrage seems to use them a lot so I think I might get some.

Any input is appreciated, thanks.

Sulaiman - 3-2-2017 at 09:40

I use Erlenmeyer flasks for vacuum filtration with little worry of implosion
because the Erlenmeyer'sf or vacuum are thick and/or shaped for vacuum,
thick glass experiences much more stress than thin glass whith rapid temperature changes or steep temperature gradients,
I do not fancy an Erlenmeyer with heat, vacuum, and a flat bottom.
but the overall cost of going to a vacuum system makes the cost of a few flasks insignificant.
I like the stability and ease of heating and ground neck of Erlenmeyers.

JJay - 3-2-2017 at 17:32

I hardly ever use Erlenmeyers, but I do like how they can be heated directly on a hotplate and stand up on their own.

I recently started using table salt baths. They take a while to heat up and would make a mess if spilled but are much less messy than oil baths and can reach higher temperatures. I think heating blocks would be even better, but they are expensive.

Usually, if doing a reaction that requires a ground glass joint, I would want the Erlenmeyer to be clamped to a stand anyway, so their ability to stand on their own is less of an asset than one would think... and usually I just use beakers for reactions that don't require ground glass joints, so I hardly ever use Erlenmeyers.

For precise temperature control, it's really hard to beat a multi-neck round-bottom flask in an oil bath.

How to regulate water flow ?

Sulaiman - 7-2-2017 at 02:16

For the next phase of my distillation experiments I will need to regulate the flow of cooling water through various condensers,
using water at pressure from the domestic supply.
When I recently ran a few distilations I had to re-adjust the garden tap several times to maintain a specific flowrate,
(possibly due to the rubber washer slowly relaxing after being compressed for so long),
I also noticed random changes in water pressure,
(probably due to varying local demand)

What is a cheap and easy way to get a constant flowrate from a varying pressure water supply ?

Worst case ... I'll use a header tank.

wg48 - 7-2-2017 at 04:33

Quote: Originally posted by Sulaiman

What is a cheap and easy way to get a constant flowrate from a varying pressure water supply ?

Worst case ... I'll use a header tank.

Pressure reducing regulators are available. For example Screwfix has them for a round £25. But becarful as not all of them can be adjustable down to zero pressure. I got one in a B&Q sale. It does go down to zero pressure but its regulation wrt to flow rate is poor but if its only suppling a continuous flow that may not matter.

If your into skip diving you can find old header tanks complete with the ball cock and fittings in them as modern boiler replacements are direct feeds.

Capacity of soxhlet

Geocachmaster - 7-2-2017 at 12:20

I was thinking of buying this Soxhlet extractor, but I was wondering about the capacity. It says 250ml, so I would think that the volume in the extractor is 250cc. However, based on the picture I would say it looks like the extractor could hold 125ml.

Does the 250ml refer to the volume of the chamber or the amount of solvent to be used with it? Perhaps the picture is of a 125ml one or my estimates are off by a factor of two.

Edit: That was a stupid question, it says right in the listing that I has a 75ml capacity, I should really pay more attention. In that case the "250ml" likely refers to the size flask meant to be used with it.

If anyone else was confused like me the soxhlet size is not actually its volume, the actual capacity of the soxhlet is much less.

[Edited on 2/8/2017 by Geocachmaster]

Sulaiman - 8-2-2017 at 03:10

I had a brilliant but simple idea,
I will supply cooling water for my condensers via a tube siphoning from a toilet cistern
... that is already available, my upstairs bathroom.

I'll just have to put a notice

PLEASE DO NOT FLUSH ... DISTILLATION IN PROGRESS

Amos - 8-2-2017 at 11:29

Quote: Originally posted by Geocachmaster

I usually use an air bath for heating RBFs because it is simple, although it suffers in efficiency. For better heating, larger quantities or high temperatures I use a water or oil bath. Twice now I have spilled the oil bath which leads to a huge mess and oil all over the bench and hotplate. I am now contemplating buying a bunch of jointed erlenmeyers. There would be more heat transfer to the flask and better stirring. For simple distillations and reflux I don't usually need more than one neck, and addition can be through the condenser if needed. Is there any reason why RBFs are so much more popular than erlenmeyers? Are they superior? Nurdrage seems to use them a lot so I think I might get some.

Any input is appreciated, thanks.

just wrap a foil skirt around your RBF, encapsulating the entire surface of the hot plate in with the flask. The increase in heating efficiency is massive, perhaps better than direct contact. Similarly I place a wall of foil around large beakers or erlenmeyers in contact with the hot plate to reduce heat loss from the sides of the container.

TheNerdyFarmer - 9-2-2017 at 05:27

Hello, I was going to make sodium nitrite via heating sodium nitrite with carbon in the presence of calcium hydroxide. I got this off of the SM wiki and it did not specify what temperature the reaction was to be heated to. If some of you have tried this method please do let me know if it is worth doing.

Question

TheNerdyFarmer - 10-2-2017 at 15:04

What is calcium hydroxide soluble in. And for future reference, how to do find the solubility of chems in organic solvents and alcohols ect. I can never find it online.

[Edited on 10-2-2017 by TheNerdyFarmer]

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