Мұқтажсыз қосылыстардың элементтік құрамын анықтау әдістері

Analytical method used to investigate elemental composition of inorganic compounds
Classical qualitative inorganic analysis is a method of analytical chemistry which seeks to find the elemental composition of inorganic compounds. It is mainly focused on detecting ions in an aqueous solution, therefore materials in other forms may need to be brought to this state before using standard methods. The solution is then treated with various reagents to test for reactions characteristic of certain ions, which may cause color change, precipitation and other visible changes. Qualitative inorganic analysis is that branch or method of analytical chemistry which seeks to establish the elemental composition of inorganic compounds through various reagents.

Salt Colour 1 MnO, MnO2, FeO, CuO, Co3O4, Ni2O3; sulfides of Ag+, Cu+, Cu2+, Ni2+, Fe2+, Co2+, Pb2+, Hg2+, Bi3+, Hg, BiI3, Bi(s), Cu(SCN)2, Sb(s), Hg2O(s), Cu[C(=NH)S]2(s) Black 2 Hydrated Cu2+ salts, Co[Hg(SCN)4](s), Blue 3 HgO, HgI2, Pb3O4, Hg2CrO4(s), Ag2CrO4(s), Red 4 Cr3+, Ni2+, hydrated Fe2+ salts, Hg2I2(s), Cu(C7H6O2N)2(s), CuHAsO3(s), Green 5 Hydrated Mn2+ salts Light Pink 6 KO2, K2Cr2O7, Sb2S3, Ferrocyanide, HgO, Sb2S3(s), Sb2S5(s) Orange 7 Hydrated Co2+ salts Reddish Pink 8 Chromates, AgBr, As2S3, AgI, PbI2, CdS, PbCrO4(s), Hg2CO3(s), Ag3PO4(s), Bi(C6H3O3)(s), Cu(CN)2(s), Ag3AsO3(s), (NH3)3[As(Mo3O10)4](s), [SbI6]3 (aq), Yellow 9 CdO, Fe2O3, PbO2, CuCrO4, Ag2O(s), Ag3AsO4(s), Brown 10 PbCl2(s), Pb(OH)2(s), PbSO4(s), PbSO3(s), Pb3(PO4)2(s), Pb(CN)2(s), Hg2Cl2(s), Hg2HPO4(s), Al(OH)3(s), AgCl(s), AgCN(s), Ag2CO3(s), Bi(OH)2NO3(s), Bi(OH)3(s), CuI(s), Cd(OH)2(s), Cd(CN)2(s), MgNH4Also4(s), SbO. Cl(s), Sb2O3(s), White

According to their properties, cations are usually classified into six groups. Upon treatment with concentrated sulfuric acid, oxalates yield colourless CO2 and CO gases. These gases burn with a bluish flame and turn lime water milky. Oxalates also decolourise KMnO4 and give a white precipitate with CaCl2.

The 3rd group of anions consist of SO, PO and BO. They react neither with concentrated nor diluted H2SO4. Sulfates give a white precipitate of BaSO4 with BaCl2 which is insoluble in any acid or base. Phosphates give a yellow crystalline precipitate upon addition of HNO3 and ammonium molybdate and heating the solution. Borates give a green flame characteristic of ethyl borate when ignited with concentrated H2SO4 and ethanol.

Qualitative inorganic analysis is now used only as a pedagogical tool. Modern techniques such as atomic absorption spectroscopy and ICP MS are able to quickly detect the presence and concentrations of elements using a very small amount of sample.

The sodium carbonate test (not to be confused with sodium carbonate extract test) is used to distinguish between some common metal ions, which are precipitated as their respective carbonates. The test can distinguish between copper (Cu), iron (Fe), and calcium (Ca), zinc (Zn) or lead (Pb). Sodium carbonate solution is added to the salt of the metal. A blue precipitate indicates Cu2+ ion. A dirty green precipitate indicates Fe2+ ion. A yellow brown precipitate indicates Fe3+ ion. A white precipitate indicates Ca2+, Zn2+, or Pb2+ ion. The compounds formed are, respectively, basic copper carbonate, iron(II) carbonate, iron(III) oxide, calcium carbonate, zinc carbonate, and lead(II) carbonate. This test is used to precipitate the ion present as almost all carbonates are insoluble. While this test is useful for telling these cations apart, it fails if other ions are present, because most metal carbonates are insoluble and will precipitate. In addition, calcium, zinc, and lead ions all produce white precipitates with carbonate, making it difficult to distinguish between them. Instead of sodium carbonate, sodium hydroxide may be added, this gives nearly the same colours, except that lead and zinc hydroxides are soluble in excess alkali, and can hence be distinguished from calcium. See qualitative inorganic analysis for the complete sequence of tests used for qualitative cation analysis.