Questions tagged [experimental-chemistry]

This tag should be applied to questions relating to the theory, design, techniques or performance of chemical experiments. This includes but is not limited to theoretical structures, expected products, thermal calculations, and empirical analysis. Additional tags should be applied to narrow down the field of research.

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5
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1answer
23k views

Why is crystalline aspirin washed with chilled water in the purification process?

Take as example this or even better this: Wash the crystals with 2-3 ml of chilled water. Why does the aspirin need to be cooled down? And why do we wash the aspirin with chilled water?
2
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1answer
3k views

Identification of zinc/aluminium/magnesium with copper sulphate solution

We are doing an experiment and would like to be able to identify zinc/aluminium/ magnesium . Would a copper sulphate solution work ? I hear that it turns black on contact with zinc, stays clear on ...
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4answers
121k views

How come water would not affect the results of a titration?

We were told to rinse the buret with the base so that the concentration won't be messed up, but when it comes to the flask that is going to hold the acid, there is no need to rinse, because it would ...
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0answers
1k views

Why are multiple extractions better than a single extraction? [duplicate]

I'm extracting $\ce{N-(4-butoxyphenol)-N'-(4-dimethylaminophenyl)thiourea}$ from thiombutosine (anti-leprosy drug) tablets. I'm doing this extraction with hot ethanol. My question is why are 4 ...
6
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2answers
7k views

Why is a volumetric flask shaped the way it is?

A volumetric flask does not look like an Erlenmeyer flask, but has more of a pear shape. Is it just to distinguish more easily between them while they are on the shelf?
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3answers
1k views

What chemical test can differentiate secondary and tertiary alcohols?

I have to perform a chemical test to determine whether the solution is a secondary or a tertiary alcohol. How can I do this? Please explain the procedure and the apparatus.
3
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1answer
2k views

Preparation of phenylamine/aniline

This is the procedure I carried out in class: Reduction of nitrobenzene by using tin and $\ce{HCl}$ acid After the completion of the reaction, $\ce{NaOH}$ added to neutralize excess acid and dissolve ...
18
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2answers
8k views

What exactly happened when I added KOH to hydrogen peroxide?

I recently added a potassium hydroxide, $\ce{KOH}$, pellet to a small droplet of hydrogen peroxide (30 %), $\ce{H2O2}$. You could clearly see the potassium hydroxide dissolving in the droplet when ...
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2answers
484 views

Different techniques of distillations

I know that fractional distillation is used to separate two liquids that are miscible in one another and have close boiling points. However, I am really confused about vacuum and steam distillation - ...
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2answers
161 views

What is the process involved in performing a mass spectrometry experiment?

I have heard that mass spectrometry is very time consuming: why is this? What is the process involved in performing a mass spectrometry experiment? What steps are the most time consuming?
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1answer
880 views

What is the difference between the reactivity of Lead subacetate and Lead II acetate undergoing a hydrothermal process?

I am attempting to adapt a hydrothermal method for synthesizing $\ce{PbS}$ nanocrystals to my school that contains a mixture of cationic and anionic surfactants sodium dodecyl sulfate (.05 mmol, SDS) ...
1
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1answer
78 views

Explain isotopic uranium/perchloric acid digestion [closed]

What is happening in this video? Can you explain this technically as well as in layman's terms? I'll summarize it. I see a technician moving fuming mixtures of presumably uranium and organic ...
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0answers
28 views

To model early fluid flow which types of pumps should be used?

I have I microchannel test rig , I want to push a 150-300 ml/hr from water in my test , I would like to know which pump type i can use ?
2
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1answer
177 views

Extraction of a pyridine tetrazole from the aqueous phase

I have synthesised a compound which is basically a pyridine ring connected to a tetrazole. The procedure suggested to precipitate it at pH 1, but it did not precipitate. It then suggested to extract ...
4
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1answer
3k views

Why should one perform an extraction with multiple small portions of solvent as opposed to one large portion?

I'm performing a liquid-liquid extraction on a 1 l water sample for GC analysis. The procedure calls for three extractions with 50 ml of dichloromethane. Would one extraction with 150 ml produce a ...
5
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3answers
2k views

Why is filter paper fluorescent?

Typical filter paper used in chemistry lab (e.g. Whatman #1) exhibits autofluorescence in near UV with excitation maximum at 365 nm and emission maximum at 440 nm. It was reported in literature1 that ...
9
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1answer
1k views

Questions about Buffer System (Lab)

I will be doing a lab on Hydrogen Phosphate buffer system tomorrow and I have a few questions about the buffer system. I am not sure if my assumptions are correct. (1) What would happen to the rate ...
6
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2answers
751 views

Steam distillation- how it actually works?

To obtain phenylamine after it is formed from the reduction of nitrobenzene with tin, we carried out steam distillation. This is what I learned in class: "During the process,steam is injected into ...
2
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1answer
2k views

Why can we not use water instead of blank control solution in enzyme catalysis with Peroxidase experiment?

I have to do a lab about enzyme catalysis with Peroxidase in my Chemistry class. We are to use the blank control solution in the experiment. My question is, why can we not use water instead? I did ...
6
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3answers
47k views

What's Standardization, and why do it?

Surprisingly, there are very few resources online (outside of obscure lab pages) that explain exactly what standardization is (not even Wikipedia!). The context is the phrase standardize the titrant ...
-2
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1answer
810 views

How alkanes can be prepared by aldehydes and ketones? [closed]

Preparation of alkanes by aldehydes and ketones, its chemical reaction and mechanism.
5
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2answers
190 views

Getting to use the lab! [closed]

Today I finally mustered the courage to go and talk to the director of the labs to politely ask him if I could use the labs out of class hours. Long story short, our lab sessions "are bad" because we ...
6
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4answers
419 views

How do I create a concentrated solution of singlet oxygen (in the dark)?

Without appealing to reactions that require photons / light, how do chemists achieve a very high concentration of continually produced, though quite short lived, singlet oxygen in aqueous solution (i....
4
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2answers
1k views

How to demonstrate the safety of wearing leather shoes in the chemistry lab?

Quite often (from my own experience anyway), one of the safety rules in a school (high school or university) laboratory is that the students must wear leather shoes. I like to demonstrate some of ...
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2answers
2k views

What does “EM grade” mean

I'm looking at purchase orders and I see purchases for chemicals like the following. Glutaraldehyde, EM Grade, 25% What does the "EM Grade" mean in this text? It says that it's recommended for ...
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3answers
1k views

Alternatives to Ring Stands

I'm trying to find an alternative to simple ring stands to hold a simple electrochemical cell. The issue is that it is difficult to adjust the height to the right position to within even a couple ...
9
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0answers
181 views

How to get defect-energy level diagram from PL data

I am reading this article Phys. Chem. Chem. Phys. , 2011, 13, 14902-14905 and seen that the authors have drawn a image of defect level using PL data Can you explain me how this diagram can be drawn ...
4
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1answer
487 views

Belousov-Zhabotinsky reaction

The Belousov-Zhabotinsky reaction is a very fascinating one. The Chemistry behind the reaction concerns thermodynamics and equilibrium. I want to perform the experiment, but I'm not able to find ...
30
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3answers
80k views

Chemistry behind Gale's coffee maker in Breaking Bad

Is there a scientific basis for the coffee making equipment which Gale Boetticher describes in Breaking Bad? He talks about maintaining the right conditions for bringing out the coffee flavor without ...
4
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2answers
2k views

Internal vs external steam distillation

To extract essential oils from plant matter (amongst other purposes), steam distillation is often used. I've seen a lot of different glassware setups for this. I've sometimes seen them broken into two ...
5
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2answers
22k views

Why are NaCl and NaBr not soluble, whereas NaI is soluble in acetone (in the Finkelstein reaction)?

My book states that: Finkelstein reaction is particularly useful for preparing iodoalkanes. The iodoalkanes are obtained by heating chloro or bromoalkanes with a concentrated solution of sodium ...
2
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1answer
211 views

Changes in defects in a material due to heat treatment

Currently i am doing some research on optical properties of a oxide material and for that purpose i have done some photoluminescence study on it. Because this is an ongoing research i cant divulge ...
3
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1answer
164 views

Propagation of uncertainty

Question related to uncertainty propagation. I was taught that when adding/subtracting measurements, add the absolute uncertainties, and when multiplying/dividing measurements, add the relative ...
2
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0answers
85 views

Reference to find dielectric constants and dielectric relaxation time

I am working on a Master degree and need to know the following data : The static (low frequency) dielectric constant of isopropanol at 25 °C The Optical (high frequency) dielectric constant of ...
10
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1answer
2k views

Calculation of Atomic weight percentage in AAS

I am currently doing doping studies in a system similar to this ($\ce{A_{x}B_{1-x}}$) and I have to find atomic weight percentage of $\ce{B}$ element using atomic absorption spectroscopy(AAS). I have ...
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1answer
12k views

How to find the concentration of potassium permanganate in this experiment?

I completed a titration experiment in a lab. The aim was to find the concentration of the titrant $\ce{KMnO4}$ solution by titrating it with a sodium oxalate solution of a known concentration. I ...
0
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1answer
307 views

What are the states of HX when reacting with alcohol and alkenes respectively, and Br2 when reacting with benzene?

I couldn't find this in any textbooks, so I guess I will ask this here. What is the physical state of $\ce{HX}$ when reacting with alcohol (nucleophilic substitution) and alkenes (electrophilic ...
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2answers
9k views

How is iron(III) chloride changed from solid to solution?

I'm conducting an experiment using iron(III) chloride in aqueous solution, but am also aware that it's usually a solid. How is iron(III) chloride experimentally converted to a solution? And can you ...
2
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1answer
3k views

How can I determine the boiling point of a compound using simple distillation?

I've graphed a distillation curve (temperature against volume of distillate) from the data obtained from a simple distillation experiment. The substance can be any of methanol, ethanol, 1-propanol or ...
10
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2answers
3k views

How to quickly cool a test tube without cracking it?

Is there a way to safely cool a heated test tube quickly without cracking it due to sudden thermal stress in the glass? One thing that I tried was blowing on it, cooling it in slightly lukewarm water ...
2
votes
1answer
756 views

How to properly work with potassium HMDS

What is the proper procedure for working with KHMDS? I would like to use it to deprotonate a compound and have a bottle of KHMDS in toluene. Does it need to be handled under inert atmosphere? And ...
5
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1answer
5k views

How would one go about making a cheap freeze spray?

I'm interested in making a liquid freeze spray, for a fun science project. My only experience with this comes in spraying inverting canned air dusters, which spray a -60F mist/liquid (liquid if you ...
3
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2answers
6k views

Does a sulfuric acid/nitric acid mixture dissolve PTFE (ie. teflon)?

In our lab, we commonly use a mixture of sulfuric acid and nitric acid to clean borosilicate glassware. I'd like to clean some PTFE pieces in there, too, but not sure if they will dissolve or not. ...
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1answer
167 views

preparation methods of nicotinoyl glycine

How can we prepare nicotinoyl glycine from nicotinic acid ?Is that possible by reaction between nicotinic acid and glycine?
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1answer
2k views

$\beta$-mercaptoethanol molarity

I'm writing up a practical and $\beta$-mercaptoethanol was used, with no concentration given. I've found I don't need the BME molarity since I'm giving percentage (v/v) concentration, however I'm ...
4
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1answer
521 views

Why is nicotinoyl chloride available as its hydrochloride salt? How can we separate them?

Nicotinoyl chloride is only available as its hydrochloride salt. Why can't nicotinoyl chloride be synthesized in free form? How can we seperate nicotinoyl chloride from its salt form? Can we try any ...
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3answers
236 views

Vacuum Distilled Medicine

If I were to buy/build a large still, that was air tight, and could hold a vacuum, and filled the reservoir with vegetable glycerin (which has a boiling point higher than the majority or desired ...
3
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1answer
123 views

Less maintenance-dependent continuous pH testing

I am creating an automated chemical component mixing system (DIY project). One of the features required is continuous monitoring of pH value in my main solution. I do not need it to be very precise, ...
6
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2answers
237 views

Removing titanium from tantalum crucible

I'm trying to remove titanium filling from a tantalum crucible for a high-temperature effusion cell. I've managed to get a majority of the material out with tweezers, but some remains and is ...
9
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1answer
784 views

Is it safe to condense water into a liquid nitrogen trap?

I'm trying to remove water from an imidazolium salt (i.e. dry the salt). However I want to know if it is safe to remove the water under vacuum. Is it safe to condense water into a liquid nitrogen ...