Sandbox II has become as clogged as Sandbox I was (and is), especially for users with 10,000 reputation or above. So, here is a new new post...

Before you delete a post here, please reduce it to one line without MathJax.

Old formatting sandboxes:

  • $\begingroup$ Why do we have to reduce it to one line without MathJax? $\endgroup$
    – Micelle
    Jun 19, 2020 at 14:53
  • 9
    $\begingroup$ @Micelle deleted posts are viewable by users with >10,000 reputation, so it's just a courtesy thing. Long mathjax posts make the page load slowly. $\endgroup$ Jun 19, 2020 at 14:55
  • 1
    $\begingroup$ @orthocresol, moving your comment explanation into the question would improve it. $\endgroup$ Feb 9, 2022 at 15:00

11 Answers 11


Common misspellings

This table is indexed alphabetically in the first column. Please feel free to add to it.

The second column contains a link to the appropriate Wikipedia page.

Wrong Correct Remarks
Breddts Bredt’s [rule] Julius Bredt.
carbonation carbocation Carbonation is what you do to make fizzy drinks.
Clemenson Clemmensen [reduction] Erik Christian Clemmensen.
die dye “Die” is only for “die Farbstoffe”.
Diel's Adler Diels–Alder [reaction] Otto Paul Hermann Diels; Kurt Alder.
fajan's Fajans’ [rules] Kazimierz Fajans
flourine fluorine
Friedel–Craft's Friedel–Crafts The guy's name was James Crafts, not James Craft.
gasses gases One outgasses gases.
Gibb's Gibbs [energy] Josiah Willard Gibbs.
Henderson–Hasselbach Henderson–Hasselbalch [equation] Lawrence Joseph Henderson; Karl Albert Hasselbalch.
iconic ionic [bond]
morality molarity The moral of this story is that only people can be moral or amoral.
Nerst Nernst [equation] Walther Hermann Nernst.
phosphorous phosphorus This refers to the element (as a noun, not adjective). See also next entry.
phosphorus acid phosphorous acid This refers to the acid $\ce{H3PO3}$. See also previous entry.
pie pi/π [bond] Pie bonding is for SeasonedAdvice.SE.
seperation separation [process] “Seperate” is not even an English word.
stigma sigma/σ [bond] Stigma bonding is for Christianity.SE or MedicalSciences.SE.
Tollen's Tollens’ [reagent] Bernhard Tollens.
Vander-Wal's, Van der walls van der Waals [force] Johannes Diderik van der Waals. Note it's lowercase “v”.
Vant-hoff van 't Hoff [equation] Jacobus Henricus van 't Hoff.

Somebody complained that the reaction I asked about doesn't exist. Why is this a problem?

Chemistry is an experimental science first and foremost, and this is especially true of synthetic chemistry, whether organic or inorganic.

What this means is that: we don't come up with theories from first principles, then use them to predict reactions. [We're getting better at doing this using quantum mechanics, but it's still very early days.] Instead, we find out that a reaction happens, and then we work backwards to come up with a model that explains it.

The ultimate source of "truth" in chemistry is not defined by our theories, but rather by our experimental observations. The theories only exist because they can explain experimental evidence.

[Incidentally, that's why there are so many exceptions to the theories. Many of them have a limited range of validity, in that they can only explain a certain subset of the experimental observations we have. A simple example is the octet rule. It works for quite a lot of organic molecules, but can completely fall apart in other contexts.]

So, asking "why does this reaction occur?" is only sensible if that reaction has actually occurred!

If nobody has done it before in real life, then we have no way of knowing whether it would actually occur. And secondly, if it doesn't actually occur and we come up with a theory to explain it, then there is no guarantee that that theory would be correct.


Temporary place to get answers and such put together. Everything I post here will be deleted in a couple of days or so. A tidy sandbox is a good sandbox!

As per the suggestion by moderator Rob, this is a partial answer to the OP’s question regarding the six spurious spots they observe when sending a red laser pointer’s beam through a calcite crystal. It appears that the ordinary and extraordinary rays are present, as expected, though maybe not well resolved due to the short path lengths.

My first thought was that the light intensity was too high, causing spurious reflections from the faces of the calcite crystal. Jon Custer suggested seeing what would happen if the crystal was rotated. Since these are easy things to test, I did so.

The figure below shows my simple setup: red laser pointer, low quality calcite rhomb, and scrap paper screen. The ruler provides the scale. Red laser and calcite rhomb 1

This replicates what the OP did, but only the too intense ordinary and extraordinary rays are revealed by the spots on the paper screen. No array of 6 extra spots. Rotating the calcite rhomb variously did nothing significant. So my working hypothesis met the fate most do: it failed.

So next I attenuated the laser intensity by a factor of 100 using a neutral density (ND) filter of optical density 2. The next figure shows the result. Red laser and calcite rhomb 2

Nicer looking spots for the ordinary and extraordinary rays, but no extra spots evident.

Another try, with my higher quality calcite rhomb and ND 3 attenuating filter between the laser and calcite rhomb. Red laser and calcite rhomb 3

No real change from the previous figure. At this point, I sent an e-mail to a friend (AChem) who is a high rep user at the chemistry stack exchange. He replied that “I think he does not have a single crystal. You can see a plane of bonded crystals. I don't know if that is causing artifacts.” He gave me permission to raise this possibility, so I posted it in a comment.

Here is the OP’s cropped image, with arrows showing how it might be two pieces stuck together.

enter image description here

The OP commented that this makes sense, but even if this is correct, what is the cause of the 6 extra spots the OP has observed?

  • 1
    $\begingroup$ Cheers Ed, I've screenshotted this! I use Engineering Equation Solver (EES) so should be able to get something going in there :) $\endgroup$
    – Hendrix13
    Aug 13, 2022 at 3:12

$h=\frac{I_{\text{const}}\cdot R_{\text{ref}}(1+\alpha\Delta T)}{A_{\text{filament}}(T-T_{\text{flow}})}$

  • $\begingroup$ Do you still need this? I've upvoted it only so that it stops triggering this question to get bumped up by the "community user". $\endgroup$ Sep 26, 2022 at 19:22
  • $\begingroup$ @user1271772 I don't need it anymore, I guess. What do you want to do? Remove all the answers? Delete the post itself? In any case, I don't mind a post getting bumped all the time in meta. Just saying. $\endgroup$ Sep 27, 2022 at 6:52

The following are the definitions of 'mole' represented in the form of equations:

(1) Number of moles of molecules $=\frac{\text { weight in } g}{\text { molecular weight }}$

(2) Number of moles of atoms $=\frac{\text { weight in } \mathrm{g}}{\text { atomic weight }}$

(3) Number of moles of gases $=\frac{\text { volume at NTP }}{\text { standard molar volume }}$ (Standard molar volume is the volume occupied by 1 mole of any gas at NTP, which is equal to $22.4$ litres.)

(4) Number of moles of atoms / molecules / ions / electrons $=\frac{\text { no. of atoms } / \text { molecules } / \text { ions } / \text { electrons }}{\text { Avogadro constant }}$

(5) Number of moles of solute $=$ molarity $\times$ volume of solution in litres or no. of millimoles = molarity $\times$ volume in $\mathrm{mL}$.

$\frac{\text { Millimoles }}{1000}=$ moles

(6) For a compound $\mathrm{M}_{\mathrm{x}} \mathrm{N}_{\mathrm{y}}, x$ moles of $\mathrm{N}=y$ moles of $\mathrm{M}$

  • $\begingroup$ Do you still need this? I've upvoted it only so that it stops triggering this question to get bumped up by the "community user". $\endgroup$ Sep 26, 2022 at 19:22
Substance $\Delta H^\circ_\mathrm{f}$ / $\pu{kJ mol-1}$ $\Delta G^\circ_\mathrm{f}$ / $\pu{kJ mol-1}$ $S^\circ_\mathrm{f}$ / $\pu{J mol-1 K-1}$
$\ce{CH4(g)}$ $-75$ $-51$ $186$
$\ce{CO(g)}$ $-111$ $-137$ $198$
$\ce{CO2(g)}$ $-394$ $-394$ $214$
$\ce{H2O(l)}$ $-286$ $-237$ $70$
$\ce{H2O(g)}$ $-242$ $-229$ $189$
$\ce{O(g) }$ $249$ $232$ $161$
$\ce{O2(g) }$ $0$ $0$ $205$
$\ce{O3(g) }$ $143$ $163$ $239$
$\ce{H2(g)}$ $0$ $0$ $131$
$\ce{C(s)}$ $0$ $0$ $6$
  • 2
    $\begingroup$ :P Well, if you'll forgive me: the negative numbers should be written with actual minus signs, hyphens are a bit shorter. IMO the easiest is to just use MathJax for everything, i.e. do $-75$, that will automatically use minus signs and also makes the font a bit more consistent throughout. $\endgroup$ Apr 19, 2022 at 12:24
  • $\begingroup$ @orthocresol Next thing, I'll worry about left or right justification of the items... $\endgroup$
    – Karsten Mod
    Apr 19, 2022 at 12:38
  • $\begingroup$ Yeah, it would be nice to have the numbers aligned after the negative sign! $\endgroup$ Apr 19, 2022 at 12:40
  • $\begingroup$ @KarstenTheis My take on this is to align numbers by a decimal point and flush them right. Since MD tables are r̶̶e̶̶t̶̶a̶̶r̶̶d̶̶e̶̶d̶̶ limited in terms of formatting options, just align the numbers right with |--:| and, if applicable, round them up to the same decimal point so that one can easily visually compare the values. Also, I think missing values are better denoted with "NA" rather than with an em dash, and a slash serves a better (and mathematically correct) separator for quantity symbols and units in a header. $\endgroup$
    – andselisk Mod
    Apr 19, 2022 at 12:58
  • 1
    $\begingroup$ @andselisk I am learning more today than my students this entire semester. I changed it to "0" instead of "NA" for the elements in their most common allotrope. $\endgroup$
    – Karsten Mod
    Apr 19, 2022 at 14:39
  • 1
    $\begingroup$ @KarstenTheis One more thing: if you have a choice, it's better to use a font with monospaced numbers. Zero wiggle in character length assists a lot with the visual comparison of long numbers. $\endgroup$
    – andselisk Mod
    Apr 19, 2022 at 15:55

select Id as [Post Link], body from posts where OwnerUserId = 72973 and (body like '%gif%')
































































  • $\begingroup$ Wow, Karsten, these are very cool “answer helpers”! Nice work! $\endgroup$
    – Ed V

I've noticed references to the $(k)$ for the saponification reaction above to be about $$\frac{6}{M\hspace{5 pt}min}$$ or slower. Which would mean at 0.1 M concentrations, while the reaction happens faster, it could still be observed. We could further this ability by decreasing the temperature further as well.

  • $\begingroup$ You could do: $\pu{6 M-1 min-1}$ $\pu{6 M-1 min-1}$ to get the units upright correctly -- there's also the MathJax faq which gives a nice bunch of examples chemistry.meta.stackexchange.com/q/86/16683. $\endgroup$ Oct 24, 2022 at 15:12
  • $\begingroup$ Thanks! I really appreciate this! I don't know why I was trying to put M^-1, I think that's because of the mhchem plugin. I'm definitely trying to drink water from a firehose when it comes to learning LaTeX and mhchem all at once! :-) Thank you @orthocresol. $\endgroup$
    – Avogadro StaffMod
    Oct 24, 2022 at 15:18
  • $\begingroup$ No prob -- generally, in LaTeX (and MathJax) if your exponent consists of more than one characters you need braces, so $\mathrm{M}^{-1}$ would give you $\mathrm{M}^{-1}$. To typeset the whole quantity correctly, with just built-in commands, you'd need something like $6~\mathrm{M}^{-1}~\mathrm{min}^{-1}$ $6~\mathrm{M}^{-1}~\mathrm{min}^{-1}$. The \pu command is basically syntactic sugar for this. (Though, if it was an actual LaTeX document, most people would recommend the siunitx package... that's an entirely different story!) $\endgroup$ Oct 24, 2022 at 15:41

$$ \begin{comment} Commented code \end{comment} $$

  • $\begingroup$ $%comment$ $%comment$ $%comment$ $%comment$ $%<comment>$ $%comment$@Avogadro, comment doesn't seem to be the right environment to use for this. $%comment$ would render better. It doesn't exist in MathJax from what I see. $\endgroup$ Oct 26, 2022 at 15:30

$%<Comment>$ "<>" renders in answers but not in comments?

enter image description here

Comment to Avogadro's post here. Worked in my comments

  • 1
    $\begingroup$ $\pi here doesn't leak through: $\pi$ $\endgroup$ Jan 30, 2021 at 15:15
  • $\begingroup$ Do you still need this? I've upvoted it only so that it stops triggering this question to get bumped up by the "community user", but that wasn't enough because the score was -1! $\endgroup$ Sep 26, 2022 at 19:22
  • $\begingroup$ @user1271772 Funny that someone would downvote this :/ $\endgroup$ Sep 27, 2022 at 6:50
  • $\begingroup$ $%<comment>$ $\endgroup$ Oct 26, 2022 at 15:35

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