In order to detect basic radicals one of the preliminary test done is dry test tube heating. My book says that on doing so salts that would appear black when hot and cold are supposed to be Mn, Co, Ni or Cu salt. But does it refer to white salts turning black during heating or salts of any colour including black when it says that they appear black after heating?

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    $\begingroup$ This may help-ncert.nic.in/ncerts/l/kelm207.pdf $\endgroup$ – JM97 Sep 16 '16 at 14:39
  • $\begingroup$ @JM97 The problem is not the language of the book neither the colour of the sample that it could be after heating but the condition which may apply(I suppose) to the salts before we heat and observe the colour change. Do these inferences apply to salts of any colour transforming into the mentioned colours or only white salts? $\endgroup$ – Tyto alba Sep 16 '16 at 14:59
  • $\begingroup$ The cations you mentioned in my knowledge do not form any black color salts. But technically, any color salt which may turn black might be from these cations. $\endgroup$ – Amritansh Singhal Sep 16 '16 at 15:02
  • $\begingroup$ @SanjuktaGhosh could you upload the picture of that paragraph? $\endgroup$ – JM97 Sep 16 '16 at 15:02
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    $\begingroup$ @Mithoron The obsolete (19th century) terms “acidic radicals” and “basic radicals” describe anions and cations, respespectively, in salts. They can still be found in some textbooks concerning qualitative inorganic analysis (in particular in India). $\endgroup$ – Loong Nov 17 '16 at 16:38

No when cold they can be of different colours as can be seen from the following table:

enter image description here

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