Identification Tests Carbonate

Bacillus subtilis var. including Bacillus amyloliquefaciens), 131, (S3)20 Carbohydrates (Starches, Sugars, and Related Substances), 836 Carbon, Activated, 85, (S 1)115 Carbonate Identification Test, 753 Carbon Dioxide, 87, (S 1)12 Carbon Dioxide Detector Tube, 862 Carbon Monoxide Detector Tube, 862 o-Carboxybenzeneazodimethylaniline Hydrochloride, 861 (R)-3-Carboxy-2-hydroxy-/V,/V,/V-... 

A. Mix 500 mg of sample with 2.5 g of anhydrous potassium carbonate, and heat the mixture in a platinum or nickel cmcible until it melts completely. Cool, add 5 mL of water, and allow to stand for 3 min. Heat the bottom of the cmcible gently, detach the melt, and transfer it into a beaker with the aid of about 50 mL of water. Gradually add hydrochloric acid until no effervescence is observed, add 10 mL more of the acid, and evaporate to dryness on a steam bath. Cool, add 20 mL of water, boil, and filter through ash-free filter paper. An insoluble residue of silica remains. Retain the filtrate for Identification Test B. 

Limestone, coral, and seashells are composed primarily of calcium carbonate. The test for the identification of a carbonate is to use a few drops of hydrochloric acid. The unbalanced equation is... 

The test identifies the presence of carbonate, COj ", or bicarbonate, HCOj", in the substance to be examined. Reference to carbonates and bicarbonates is made in less than five monographs, all describing simple inorganic carbonate and bicarbonate salts. The carbonate ion forms insoluble salts with nearly all cations except the alkali metals and ammonia, and the bicarbonate ion, more commonly referred to as hydrogen carbonate, generally has an even lower solubility. Hydrogen carbonate is a weak acid and is unstable in an acidic environment. This characteristic and the insolubility of barium carbonate are used in the identification test. 

Analytical and Test Methods. For a review of detection, deterrnination, and identification of ketenes see Reference 67. Typical properties are the strong ir absorption bands at 2151 cm (C—O) and at 1120 cm as weU as a very low field signal of the j hybridi2ed carbon at approximately 194 to 206 ppm and a very high field signal of the s hybridi2ed carbon at approximately 2.5 to 27 ppm in C-nmr spectroscopy. 

When a solution is tested, both analyte and solvent absorption bands will be present in the spectrum, and identification, if that is the purpose of the experiment, is hindered. Some solvents have rather simple IR spectra and are thus considered more desirable as solvents for qualitative analysis. Examples are carbon tetrachloride (CC14, only C-Cl bonds), choloroform (CHC13), and methylene chloride (CH2C12). The infrared spectra of carbon tetrachloride and methylene chloride are shown in Figure 8.21. There is a problem with toxicity with these solvents, however. For quantitative analysis, such absorption band interference is less of a problem because one needs only to have a single absorption band of the analyte isolated from the other bands. This one band can be the source of the data for the standard curve since the peak absorption increases with increasing concentration (see Section 8.11 and Experiment 25). See Workplace Scene 8.2. 

Elemental composition Pb 77.54%, C 4.49%, O 17.96%. The compound is digested with nitric acid, diluted and analyzed for lead by various instrumental techniques (See Lead). Carbonate may be tested by treating the compound with dilute HCl. It will effervesce, the evolved CO2 gas will turn hmewater milky. Also, liberated CO2 can be identified using a GC-equipped with a TCD or by GC/MS. The characteristic mass ion for GC/MS identification of CO2 is 44. 

Elemental composition Zn 52.14%, C 9.58%, O 38.28%. Zinc carbonate is identified by effervescence produced upon adding dilute HCl. CO2 evolved is identified by the lime water test or by GC or GC/MS. Characteristic mass for identification of CO2 is 44. Zinc may be analyzed in an acid solution by AA, ICP, and other methods to measure zinc content of the compound. 

---