1
$\begingroup$

Which white, ionic compound(s) that is insoluble in water turns pink when you add only a little of water but white again when you add more water?

I know that the cation is one of the following:

$$\ce{Mg^2+, Ca^2+, Sr^2+, Ba^2+, Fe^3+, Ni^2+, Co^2+, Zn^2+, Al^3+, or NH4^+}$$

I was physically examining such a compound and determined it does not change the color of litmus paper (red or blue). I thought that it could be zinc carbonate because it also precipitates hydroxide (when then compound is added to dilute nitric acid).

EDIT: I found out that the compound is lithium carbonate, and it just took a long time to dissolve. How would lithium carbonate change color like this?

$\endgroup$
  • 1
    $\begingroup$ Reversible color change reminds me immediately complexation, and in this case maybe a complex only stable when there is very less amount of water around. However, if it is really insoluble as stated I can't know. And the question is a riddle like one, do you have any effort on solving this question, if so edit and share it after the question, please. $\endgroup$ – Güray Hatipoğlu May 7 '18 at 21:05
  • $\begingroup$ I landed here because i am looking for some ingredient of ash (Wood fire, possibly some metal) that turns rose/pink if a fresh twig smoulders on top (my guess was that this is due to water vapor), but stays ash-colored in the rain. So i hope somebody will answer this. $\endgroup$ – bukwyrm Jun 28 '18 at 5:09
  • $\begingroup$ I found out it was lithium carbonate. Why did this happen? $\endgroup$ – user63881 Jun 29 '18 at 5:49
  • $\begingroup$ @Bob Where'd you get the answer from? The sources may help us. $\endgroup$ – Gaurang Tandon Jun 29 '18 at 10:48
  • $\begingroup$ I was told. The compound was known by someone else. $\endgroup$ – user63881 Jun 30 '18 at 11:46

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy