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I have never seen the highlighted symbol before. What is the name of the symbol itself, and what does it mean in this context?


The sign $≏$ is read "is chemically equivalent to". The term chemically equivalent refers to a specific chemical reaction. For the reaction $$\ce{N2(g) + 3 H2(g) -> 2NH3(g)}$$ $$\pu{1 mol } \ce{N2} \, ≏ \, \pu{3 mol } \ce{H2} \qquad \pu{1 mol } \ce{N2} \, ≏ \pu{2 mol } \ce{NH3}$$

Reference: Atkins, P. W.; Jones, L. L.; Laverman, L. E. Chemical Principles: The Quest for Insight, 6th ed.; W. H. Freeman: New York, 2012. Page no. 96, Section L: Reaction Stoichiometry.


It seems that the OP is using Chang's Chemistry. In the same book, on pg. no. 98, the meaning of the symbol is explained as "stoichiometrically equivalent to" or simply "equivalent to".

  • $\begingroup$ Well, I must admit that this is the best answer. Great find! $\endgroup$ – andselisk Jan 9 '18 at 9:34
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    $\begingroup$ @andselisk Can you make that sign $≏$ large? I tried it using $\Large{≏}$ but it is making the other text large too. $\endgroup$ – Apoorv Potnis Jan 9 '18 at 9:51
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    $\begingroup$ I used $\Large ≏$ ($\Large ≏$) in my post as a dirty hack:). \Large is basically a macro that acts as a switch, and does not take any parameters, so \Large{...} is not going to work. $\endgroup$ – andselisk Jan 9 '18 at 9:54
  • $\begingroup$ Yes, I'm using Chang's textbook, and you have a very sharp eye to spot that symbol in the textbook. Thank you. $\endgroup$ – George Tian Jan 9 '18 at 21:59
  • $\begingroup$ @GeorgeTian What I did was to simply google the first sentence of your image and Google immediately showed Chang's book and the page where it was written. $\endgroup$ – Apoorv Potnis Jan 10 '18 at 7:07

It is probably supposed to be the 'corresponds to' sign[ref, p 105]; in this case simply representing that for every two moles of $\ce{NaOH}$ one mole of $\ce{H2SO4}$ is converted by reaction stoichiometry.

This sign is difficult to typeset in LaTeX which is why I presume the authors used something else instead. Creating the sign is even more annoying in MathJax. The closest I [got at first] were

$$\overset{\lower.5em\wedge}{=}\ \text{or}\ \hat{=}$$

which are $\overset{\lower.5em\wedge}{=}$ and $\hat{=}$, respectively.

Edit. After some testing, this option $\lower.1em\lower.5em\widehat{\raise.5em{=}}$ looks best in my opinion.

$$\ce{2 mol NaOH $\lower.1em\lower.5em\widehat{\raise.5em{=}}$ 1 mol H2SO4}$$


Just the bare $\widehat{=}$ leads to

$$\ce{2 mol NaOH \widehat{=} 1 mol H2SO4}.$$

ref: E. R. Cohen, T. Cvitas, J. G. Frey, B. Holmström, K. Kuchitsu, R. Marquardt, I. Mills, F. Pavese, M. Quack, J. Stohner, H. L. Strauss, M. Takami, A. J. Thor. (2007). Quantities, Units, and Symbols in Physical Chemistry. ('IUPAC Green Book'). Third Edition. International Union of Pure and Applied Chemistry. (2008 IUPAC & RSC reprint). ISBN: 978-0-85404-433-7. [free copy]

Here is a picture of how it looks in the 'Green Book':

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    $\begingroup$ Usually one can type ≙ easier with \wedgeq $\rm \LaTeX$ command, which unfortuanety appears not to work with MathJax:) $\endgroup$ – andselisk Jan 8 '18 at 23:17
  • $\begingroup$ @andselisk What package is that from? $\endgroup$ – Linear Christmas Jan 9 '18 at 0:01
  • $\begingroup$ \wedgeq is from amssymb. $\endgroup$ – andselisk Jan 9 '18 at 0:08

I suppose it's a $\Large ≏$ "difference between" math symbol, which here denotes inequality in amounts between acid and base. Can be typed using $\rm \LaTeX$ command \bumpeq, or Unicode symbol 0x224F.

Also note that there are two more similarly looking unrelated symbols:

Also, check out relational symbol for “the same strings”. It seems that some authors use math notations quite liberally, and it might as well be that they assigned this character for something different. In order to prove or disapprove that, it would be ideal to get the full-text.

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    $\begingroup$ This alchemical symbol is so obscure, that my browser doesn't view it :D $\endgroup$ – Mithoron Jan 8 '18 at 22:43
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    $\begingroup$ Should not it be equivalence of amounts rather than inequality in amounts? $\endgroup$ – mamun Jan 8 '18 at 23:12
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    $\begingroup$ Could you explain how your interpretation of the symbol fits with the context of the sentence? In context I am inclined to go with 'corresponds to' or 'is stoichiometrically equivalent to', as has been suggested. $\endgroup$ – a-cyclohexane-molecule Jan 8 '18 at 23:32
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    $\begingroup$ That's what I was trying to say. They are stoichiometrically equivalent. Albeit, 2 mol is not equal to 1 mol, but 2 mol NaOH is capable of neutralizing 1 mol H2SO4. As a result, they are said to be equivalent (not equal), hence they have this obscure notation to differentiate these two ideas. $\endgroup$ – mamun Jan 8 '18 at 23:41
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    $\begingroup$ @a-cyclohexane-molecule (cc mamun) Trying to dig up what authors might wanted to say with this is a rabbit hole to hell. I edited the answer a bit, but to get a 100% correct interpretation the editor or the author should appear in this topic and explain the intended meaning. $\endgroup$ – andselisk Jan 8 '18 at 23:46

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