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21 votes

How can I identify the material of this mystery gear?

Xray Fluorescence This may sound like some massive "Oh sure, I'll just hop over to the nearest government lab and ask for some beamtime!" overkill suggestion, but in fact handheld XRF ...
DotCounter's user avatar
18 votes
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How is hair tissue mineral analysis performed?

The analytical technique is called inductively coupled plasma optical emission spectroscopy. It was invented by a chemist V. A. Fassel, although it is pure physics. The specimen is digested in an acid,...
AChem's user avatar
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14 votes

How can I identify the material of this mystery gear?

Your idea of checking density is good, but consider the accuracy of your results. For a small part, errors in measurement due to meniscus of water in a cylinder, or sticking to the container or gear, ...
DrMoishe Pippik's user avatar
12 votes

How is hair tissue mineral analysis performed?

Inductively Coupled Plasma (ICP) based techniques are very common for elemental analysis. The goal of such analyses is to quantify the elements present in a sample. The neat thing about this, in my ...
Yoda's user avatar
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11 votes
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Why do rare earth metal oxides vary in color so much?

TL;DR f-f transitions in lanthanide ions give rise to the colours of the ions. The electronic states can be derived from quantum mechanics, and their energies vary from ion to ion, which give rise to ...
orthocresol's user avatar
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11 votes
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How does a mercury detector work?

There are many ways to detect mercury, and you can find a more detailed analysis of these methods, along with examples of these detectors and their limitations, here. Gold film sensors Gold Film ...
ringo's user avatar
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11 votes

How does a mercury detector work?

Most commonly they work by pulling air through a UV absorption cell and simply measuring the absorption at 254 nm. Often there is a pre-concentration step involved. This usually involves a gold-...
airhuff's user avatar
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11 votes

Why are sulfites often ignored in soil studies?

I think Andrew is correct in his statement: I think it's generally assumed that sulfite has a short lifetime in soil, decomposing to $\ce{SO2}$ gas or getting oxidized to sulfate. Sulfur is found in ...
Mathew Mahindaratne's user avatar
9 votes
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Chemical elements or compounds with yellowish white color

Aluminium(III) chloride - often described as white but samples is sometimes contaminated with iron(III) chloride giving it a light yellow color Antimony(V) oxide - pale yellow solid Bismuth(III) oxide ...
Nilay Ghosh's user avatar
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8 votes
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Determining stoichiometry in ICP-OES data analysis

Let R be the ratio of number of Na atoms to number of Fe atoms. Then, for the first compound, we have $$\pu{R = }\frac{\pu{112300 ppm } /\ \pu{22.98977 g mol^{-1} } }{\pu{357200 ppm } / \ \pu{55.845 ...
Ed V's user avatar
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8 votes
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False positive test for chloride ions during lab practical

I agree with Maurice's answer, here I add some details: Moisture in the air may stabilize nitric acid against decomposition, which would keep the fumes white or at least more white. Ammonia can ...
Oscar Lanzi's user avatar
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7 votes
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Organic molecules with 21.62% oxygen

Disclaimer: Here I take the molar masses of carbon, hydrogen and oxygen to be $\pu{12g, 1g, 16g}$ respectively, which is what would be expeccted of you at school. For the sake of simplicity, let's ...
paracetamol's user avatar
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7 votes
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Why are sulfites often ignored in soil studies?

This article(ref.) gives you your answer: While techniques are available for determining the concentration of most S-oxides in soil, determination of soil sulphite has been largely neglected. This is ...
7 votes

False positive test for chloride ions during lab practical

If your powder, mixed with "mildly" concentrated sulfuric acid, produces white fumes that react with ammonia, the white fumes may be $\ce{HCl}$ , $\ce{HBr}$, or $\ce{HNO3}$. But if it is $\...
Maurice's user avatar
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6 votes

How is hair tissue mineral analysis performed?

Neutron activation analysis is a technique that can be used for trace mineral quantification in a sample. You start by irradiating your sample in a small experimental nuclear reactor. These were more ...
uhoh's user avatar
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5 votes
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Removing sodium borate for the test proving thiocyanate ions

Lehrbuch der analytischen und präparativen anorganischen Chemie by Jander et al. [1] suggests to precipitate borate with $\ce{Ba^2+}$ in neutral solution beforehand as barium(II) thiocyanate is one of ...
andselisk's user avatar
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5 votes

Chemical elements or compounds with yellowish white color

Calcium hypochlorite is an example of such a yellowish white compound. Another example would be Silver Bromide
Safdar Faisal's user avatar
5 votes

Cant figure out whether Lithium or Strontium is in my substance?

Lithium produces a red purple flame with only one big line in the spectrum. Strontium produces an orange flame with plenty of lines in the red, orange, yellow and green region of the spectrum. Lithium ...
Maurice's user avatar
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5 votes

How can I identify the material of this mystery gear?

Thanks to @DrMoishe Pippik for the suggestion to perform hardness testing on the gear. I don't have easy access to a hardness testing machine, but tested against some household objects of known ...
hifkanotiks's user avatar
4 votes

Calculation of empirical formula from elemental analysis

A sad Ph.D. student had been working on the synthesis of a natural product, with empirical formula $\ce{CH2N}$, for several years. He finally succeeded in synthesising it - or so he thought - because ...
orthocresol's user avatar
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4 votes

Removing sodium borate for the test proving thiocyanate ions

When you ask how to remove borax, I assume it is Sodium tetraborate decahydrate (Wikipedia). Thus, I agree with @andselisk of using $\ce{Ba^2+}$ solution to precipitate it. Even though it is seemingly ...
Mathew Mahindaratne's user avatar
4 votes

Chemical elements or compounds with yellowish white color

The reaction of any acid on a thiosulfate solution makes a precipitate of sulfur $\ce{S_8}$ which is pale yellow, nearly white.
Maurice's user avatar
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4 votes
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Can we use silver nitrate to distinguish between chloride and carbonate salts?

The test for Chloride ion is silver nitrate in an Acidified solution [with nitric acid]. This removes carbonate (as carbonic acid), cyanide[careful] and sulfide (as hydrogen sulfide). (Use a well-...
jimchmst's user avatar
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4 votes

Reactivity in my standard solution of Cu, P, Al, Ca, Fe, K, Mg, Mn, Na and S in 7,8% HNO3 and H2O2

The knowledge of classical chemistry remains important, irrespective of the sophistication of analytical techniques or the cost of the instrumentation. It is important to understand the ...
AChem's user avatar
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3 votes

Combustion analysis methodology question

I did this a little differently. If there were $\pu{4.5897 \times 10^{-3}}$ moles of $\ce{CO2}$ produced, that must mean that there were $1/7$ as many moles of $\ce{C7H16O4}$ present in the original ...
Chet Miller's user avatar
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3 votes
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Does ICP-OES detect molecules in suspension?

It will depend on the size of the particles which are in suspension. If the particles are very large compared with the capillary feeding the solution into the spray chamber then the capillary will ...
Nuclear Chemist's user avatar
3 votes

Lactic acid - Elementary analysis

You can check if the calculated molecular weight corresponds to lactic acid if not try next multiple like 2, then 3 etc. You get $\pu{30g/mol}$ for $\ce{C1H2O1}$ and $(\pu{90g/mol})/(\pu{30g/mol})=...
Gabriel F's user avatar
3 votes
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In TOF Mass Spectrometry how does the detector 'know' the difference between ions of different elements?

I suppose that you are referring to a Wiley–McLaren time‐of‐flight mass spectrometer [Rev. Sci. Instr. 65, 3344 (1994)] which is basically a tube containing an electrode stack for accelerating the ...
Paul's user avatar
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3 votes
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How to measure the amount of calcium in a supplement?

For the determination of calcium (at least) two methods are conceivable: gravimetric analysis Sulfate is a rather bad choice here. As compared to the carbonate, the sulfate has a much higher ...
Klaus-Dieter Warzecha's user avatar

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