By colour reactions

Colour reactions for particular homopolymers are listed in Table 6.5. These tests are rather laborious and are perhaps best regarded as confirmatory tests for polymer identifications achieved by other means. 

Combusted in oxygen-filled flask over dilute hydrogen peroxide solution Potentiometric titration of sulphuric acid with N/lOO sodium hydroxide or photometric titration of sulphate with N/lOO barium perchlorate 

Chloride titrated potentiometrically with N/lOO silver nitrate in presence of nitric acid in acetone Combustion as above 

Digested with sulphuric acid/perchloric acid 

Digest diluted with ammonium vanadate/molybdate added. Yellow phosphovandmolybdate complex evaluated at 430 nm 

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Glycerol may be detected qualitatively in small quantities by colour reactions dependent on the formation of dihydroxyacetone. 

In order to obtain sharply resolved zones, the quantity of material applied to the chromatogram should be as small as pOvSSible. RatW large sample volumes are, however, often necessary for the detection (by colour reactions) of substances that are present in low concentration this inevitably results in broadening and overlapping of zones. 

Ajmaline. The presence of the indoline was established by colour reactions, substitution reactions, e.g. bromoajmaline, and by ultraviolet absorption spectroscopy. Its N-methyl was fixed onto the indoline nitrogen since potassium permanganate oxidation in acetone gave N-methylisatinacetone and soda lime or zinc dust distillation furnished N-methylharman. 

CH3C(0)CH2Br. Colourless liquid which rapidly becomes violet in colour it is a powerful lachrymator b.p. 1367725 mm. Manufactured by treating aqueous propanone with bromine at 30-40 C it is usual to add sodium chlorate(V) to convert the hydro-bromic acid formed by the reaction back to bromine. It is not very stable and decomposes on standing. 

Colorations or coloured precipitates are frequently given by the reaction of ferric chloride solution with.(i) solutions of neutral salts of acids, (ii) phenols and many of their derivatives, (iii) a few amines. If a free acid is under investigation it must first be neutralised as follows Place about 01 g. of the acid in a boiling-tube and add a slight excess of ammonia solution, i,e., until the solution is just alkaline to litmus-paper. Add a piece of unglazed porcelain and boil until the odour of ammonia is completely removed, and then cool. To the solution so obtained add a few drops of the "neutralised ferric chloride solution. Perform this test with the following acids and note the result ... 

Dissolve 20 g, (19 -6 ml.) of anihne in a mixture of 55 ml. of concentrated hydrochloric acid (1) and 55 ml. of water contained in a 350 ml, conical flask. Place a thermometer in the solution and immerse the flask in a bath of crushed ice (2) cool until the temperature of the stirred solution falls below 5°, Dissolve 16 g. of sodium nitrite in 75 ml. of water and chUl the solution by immersion in the ice bath add the sodium nitrite solution (3) in small volumes (2-3 ml. at a time) to the cold anihne hydrochloride solution, and keep the latter weh stirred with the thermometer. Heat is evolved by the reaction. The temperature should not be allowed to rise above 10° (add a few grams of ice to the reaction mixture if necessary) otherwise appreciable decomposition of the diazonium compound and of nitrous acid wih occur. Add the last 5 per cent, of the sodium nitrite solution more slowly (say, about 1 ml. at a time) and, after stirring for 3-4 minutes, test a drop of the solution diluted with 3-4 drops of water with potassium iodide - starch paper (4) if no immediate blue colour... 

By using an aromatic aldehyde carrying an electron-releasing group the intermediate cation can be stabilized. This is the basis of the widely-used Ehrlich colour reaction for pyrroles, indoles and furans which have a free reactive nuclear position (Scheme 21). 

As regards general methods for distinguishing between the alkaloids of opium, mention may be made of the following Kofler and Kofler s study of the micro-sublimation of these alkaloids and the characters of the micro-sublimates the comparison by Maplethorpe and Evers of the picrates of a series of opium bases, comparison of the colour reactions of a series of opium alkaloids, and their behaviour with specific reagents and precipitants. ... 

Tuduranine, CjgHjgOgN. This member of the aporphine group (p. 306) is the most recent addition to Sinomenium alkaloids and was isolated by Goto from the mother liquors of sinomenine. It is crystalline, has m.p. 125° (with softening at 105°), and yields a sparingly soluble hydrochloride, m.p. 286° (dec.), [a] f — 148° (dilute MeOH), is freely soluble in alkali, and gives feeble ferric chloride and diazo-colour reactions and a fuchsin-red colour with formaldehyde and sulphuric acid. It behaves as a secondary base and yields a diacetyl derivative, m.p. 170°, [a] / — 321-71° (MeOH), which does not form a methiodide, but can be hydrolysed to A -acetyl-tuduranine, m.p. 277°, — 395-24°, and this can be methylated to... 

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