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I find it very confusing and hard to memorize.
Is there a way to deduce it, like understanding how it is derived, or is it just one of a lot of ways you can do it but is the standard one?
Do people use to test every possible reagent or combination of reagents and see if something happens or is it deducible?

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    $\begingroup$ "What is the logic behind the division into groups of anions and cations in qualitative inorganic analysis?" Well then, what's the logic behind discussing the constitution of various substances in terms of elements (and compounds thereof)? Why don't we just accept that everything is made of "something" that occupies space and has mass and just forget this whole chemistry business? <--- Food for thought $\endgroup$ – paracetamol Jan 10 '18 at 10:34
  • $\begingroup$ Well the resolution of substances into compounds and compounds into elements seems meaningful because elements are characterized by differing quantum numbers like baryon number, election number and so on. It makes sense that they would have different properties but the division of groups in inorganic analysis seems rather arbitrary and imprecise if there are more than one way to do it. $\endgroup$ – Rishi Raj Jan 10 '18 at 11:01
  • $\begingroup$ I can deduce, in some sense, the structure of the atom, elements, ideas of electrovalent and covalent bonds and then the categorization of elements with the postulates of quantum mechanics and some ideas of electrostatics. What I want to know is if there is some idea behind the categorization for qualitative analysis. $\endgroup$ – Rishi Raj Jan 10 '18 at 11:05
  • $\begingroup$ @paracetamol The logic behind discussing the constitution of compounds in terms of elements is that an element has a simple physical model and using many elements in conjunction, compounds form whose properties can be explained on the basis of the elements that form it, from the same physical model. By physical I mean, approximately physical, statistical, whatever you'd like to consider $\endgroup$ – Rishi Raj Jan 10 '18 at 11:10
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What is the logic behind the division into groups of anions and cations in qualitative inorganic analysis?

There is a somewhat established classic procedure of qualitative and quantitative chemical analysis (also known as "systematic analysis") based on treatment of the solution by specific set of reagents in specific order. Cations are divided into groups based on the stage they are detected in the procedure. There is NO other logic behind this division, nor it has any meaningful chemical significance.

Also, how does one get at the various tests, like, did people use to test every possible reagent or combination of reagents and see if something happens or is it deducible?

Somewhat deducible. Solubility product constant can be used to check if the solution is prone to precipitation of particular salt barring cases of redox reaction. For redox reactions standard electrode potentials and Nernst equation might be used for a quick check. Still, knowledge of these particular constants is mostly (if not completely) empirical.

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  • $\begingroup$ Is there a good source to get a nice grip in the entire procedure without having to conduct the experiments on my own? $\endgroup$ – Rishi Raj Jan 10 '18 at 13:28
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    $\begingroup$ @RishiRaj Search old (<90s) analytic chemistry books with chapters like "systematic analysis" that contain use of H2S. In recent years the method is virtually never used, there are X-ray spectroscopic methods that are reasonably affordable and billion times safer. Otherwise wikipedia gives reasonable qualititve description of the procedure en.wikipedia.org/wiki/Qualitative_inorganic_analysis $\endgroup$ – permeakra Jan 10 '18 at 15:10

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