An unknown solid is entirely soluble in water. On addition ofdilute HCl, a precipitate forms. After the precipitate is filteredoff, the pH is adjusted to about 1 and H2S is bubbled in; aprecipitate again forms. After filtering off this precipitate, thepH is adjusted to 8 and H2S is again added; no precipitate forms.No precipitate forms upon addition of (NH4)2HPO4. The remainingsolution shows a yellow color in a flame test. which might bepresent, might be absent, definitely absent?
