Precipitation test

Qualitative Analysis. Nitric acid may be detected by the classical brown-ring test, the copper-turnings test, the reduction of nitrate to ammonia by active metal or alloy, or the nitrogen precipitation test. Nitrous acid or nitrites interfere with most of these tests, but such interference may be eliminated by acidifying with sulfuric acid, adding ammonium sulfate crystals, and evaporating to alow volume. 

Other tests useful for the detection of unstable hemoglobins are the heat stability test, the Isopropanol precipitation test, and the PCMB or PMB precipitation test ... 

Mix 25 g 2,4,5-trimethoxyphenylacetone, 9.3 g hydroxyl-amine-HCI, 15.6 g K acetate and 400 ml 70% ethanol and reflux 3Vz hours. Evaporate in vacuum and extract the residue with 4X150 ml benzene. Wash combined extracts with 2X75 ml water dry and evaporate in vacuum the benzene (can purify the oil by dissolving in benzene and precipitate by adding petroleum ether) to get aout 20 g precipitate (test for activity). Dissolve 18.1 g precipitate in 200 ml methanol and hydrogenate. Acidify to get about 15 g (I). 

Absorbent availability could have significant impact upon process costs. Most spent alkali streams could be used depending on the other impurities present. Corrosion or precipitation tests should be considered for these cases. Any other readily available alkali, like sodium carbonate or sodium hychloride, should be considered. Slurry solutions of lime or limestone should be avoided because of past operating problems. 

Tolmetin - Tolmetin metabolites in urine give positive tests for proteinuria using acid precipitation tests (eg, sulfosalicylic acid). 

Isolation of Free Add.—To the filtrate which contains the Ca salt in solution, dilute sulphuric acid is added until all the Ca is precipitated (test), and this is filtered off and washed with a little hot water. The filtrate is then evaporated until the free acid crystallises out. 

Isolation of Sodium Salt.—The sodium salt is isolated when fusion with caustic soda is anticipated. To the filtrate containing the Ca salt in solution, sodium carbonate is added until no more CaC03 is precipitated (test). The CaC03 is filtered off and washed, and the filtrate evaporated, yielding the Na salt. 

Benzidine.—It is then removed to a basin where it is boiled up slowly with 500 c.cs. water and 120 c.cs. cone, hydrochloric acid and filtered from sine residue. A saturated solution of sodium sulphate is then added until the benzidine sulphate is completely precipitated (test). This is filtered off and is well washed with warm water until free of acid. The moist benzidine sulphate is removed, heated to 50° with a little water, and caustic soda solution (30%) added with stirring until the liquid is just alkaline (test with phenolphthalein). When cold, the free base is filtered off and dried at 50°. It may be crystallised from benzene, alcohol or from hot water (see p. 498). 

Figure 1 Comparative concentrations of tannins and alkaloids in fruits from three seed ecological groups. Data are the mean derived from all species examined. Tannin concentrations are in g g freeze dried weight, alkaloid concentrations are based on a semi-quantitative precipitation test.

Quantitative precipitation tests indicate both how much hapten-specific antibody is present and how much unconjugated protein would be required to absorb out all the antibodies directed against the protein alone. This absorption can then be done by incubating equivalence concentrations of antigen and serum and removing the precipitate. Absorption can also be done with protein-agarose affinity columns. In addition, the antibody can be purified with hapten-bearing affinity columns, from which hapten-specific antibody can be eluted with 2 M acetic acid or with excess hapten. 

Perhaps the most striking and widespread of these earlier reports is the frequent absence of characteristic anion precipitation tests found for complexes containing anions. These are especially striking where the... 

Precipitation Tests.—Several reagents possess the property of precipitating proteins from solution as unchanged protein. 

Precipitated Protein Salts.—Other acids, e.g. picric, phospho-timgstic and tannic acids, precipitate albumins from solution in the form of insoluble protein salts. The alkali salts of these acids cause no precipitation. These precipitation tests are used in salting out methods for the separation of the proteins, but the limits of differentiation are not sharp and much care is needed to make the separations valuable. More specific details as to methods of manipulation may be found in laboratory texts on physiological chemistry. 

Run Conditions Clarified supernatant liquor from liter-scale precipitation tests with... 

In addition to instrumental methods of identification, an analyst may make use of some method of microchemical testing. An excellent discussion of the latter is available5. This work is a systematic study of precipitate tests, color tests, and crystal formation for modern analgesics. Through manipulation of the various testing parameters, Clarke identified a large number of analgesics. Even with the sophisticated instrumentation now available, "wet" methods of identification are still very useful. 

Colour tests are also given by Fulton [106]. Precipitation tests are given by references [107-14 inc.], microprecipitation tests by references [5, 114-20 inc.], and other methods of detection and identification of codeine by references [121-42 inc.]. 

Colour tests are also given by Fulton [48]. Precipitation tests [49-53] and microprecipitation tests [54] have also been devised. 

Isolation of Lecithin from Egg-yolk (section 217).— Grind the yolk of one hard-boiled egg with 50 cc. of ether. Filter and wash the solid residue twice with 10 cc. of ether. Evaporate off the ether on the steam-bath, or distil it off from a small flask. Extract the residue twice with hot alcohol, using 10 cc. each time. Pour off the alcohol from the heavy oil through a small filter. Evaporate off the alcohol, dissolve the residue in 10 cc. of cold ether, and add 10 cc. of acetone. Stir until the particles of the precipitated lecithin adhere together and form a ball. Place the latter on a filter-paper. Describe its properties. Boil about one-fourth of the lecithin with about 10 cc. of a 10 per cent solution of sodium hydroxide. Note the odor of the gas evolved. What is it Cool the solution. Is there any evidence of the formation of a soap Filter, dissolve the precipitate in warm water and add dilute hydrochloric acid to the solution. What is precipitated Test a part of the lecithin for nitrogen and for phosphorus ( 58, 59, 61, page 39). 

Eqi) Filter off the precipitate, test the filtrate for a ferrocyanide and determine if the precipitate is lead dioxide, PbCh. Add hydrochloric acid to a little of the substance and heat. (Eq.)... 

The analytical results from subsequent precipitation tests conducted with TMT-15 (Table II) show that when one equivalent of TMT-15 was added for each equivalent of heavy metal present, copper (>99%), mercury (>95%), lead (79%), and cadmium (48%) precipitated from the 10-34-0. Relatively small amounts of arsenic (13%), zinc (<10%), chromium (<2%), and manganese (6%) precipitated upon addition of TMT-15. When a 50% excess of TMT-15 was used, only a small improvement in the precipitation of arsenic, cadmium, and lead was observed. 

The results of these precipitation tests with TMT-15, Thio-Red II, and 5% Na2CS3 can be understood by considering the Ksp values for related metal-ethyl xanthate complexes (22) copper and mercury have the smallest values, 10 and 10, respectively lead and cadmium are slightly higher, 10 and 10, respectively while the values for zinc and manganese are quite high, 10" and 10, respectively. 

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