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2. Fe, Clo, in neutral solutions, produces a deep red coloration. On boiling, all the iron separates as a light brown precipitate of basic acetate, and the fluid becomes colourless.
3. A strong solution heated with H2SO4 and alcohol yields acetic her, recognized by its characteristic and pleasant odour.
129. FORMIC ACID. CH,Oz.
1. AgNO3 produces, in neutral concentrated solutions, a white precipitate of CHAgO2, which rapidly darkens, especially on heating, owing to separation of Ag.
2. Fe,Clo produces a similar reaction with formates as with acetates.
3. Hg2(NO3)2 produces a white precipitate of the formate of mercury, which, however, soon becomes grey from separation of Hg.
4. Heated with H2SO4, CO is evolved, and, if lighted, burns with a blue flame.
130. Higher fatty acid.
STEARIC ACID. C18H36O2.
1. Heated with alkalies a soap is formed. Thus, with NaHO sodium stearate is formed, which dissolves in warm water and the glycerine separates. Soaps are decomposed by acids, which unite with the base, and the fat separates and may be dissolved in alcohol. From this solution the fat crystallizes in needles.
TESTS FOR ORGANIC ALKALOIDS AND
CERTAIN OTHER ORGANIC BODIES.
131. MORPHINE. C7H19N03 (Opium).*
1. KHO and (NH4)HO precipitate morphia from its salts, readily soluble in excess of KHO, less readily in excess of (NH)HO.
2. Concentrated HNO3, added to powdered morphia or its salts, produces an orange red coloration, changing afterwards to yellow. The reaction is best seen on a porcelain crucible lid. Addition of SnCl, or of Na2S2O3 destroys the colour.
3. A neutral solution of Fe,Cle produces, when added to morphia (either in the dry state or in solution), a deep blue colour.
4. HIO3, when added either to free or combined morphia, is decomposed with liberation of I, which colours the liquid brown. Starch paper added to the solution becomes blue. Addition of (NH4)HO deepens the brown colour.
5. H2SO4 produces no coloration with morphia or its salts, but on adding a crystal of K,Cr,Oy a bright green colour is produced.
132. MECONIC ACID, C,H,O, (Opium).
1. Fe,Clo produces a deep red coloration, which does not alter on boiling (like ferric acetate), nor on treatment with HgCl, (like iron sulphocyanide).
* These names refer to the substances from which the alkaloids, &c.
2. Lead acetate produces a white precipitate of lead meconate, insoluble in acetic acid.
OPIUM SOLUTIONS :
Opium contains both morphia and meconic acid ; hence, in examining solutions of opium, the reactions of both these substances are obtained. The reaction of Fe,Cle with meconic acid is highly characteristic, and as meconic acid only occurs in opium, its detection in solutions of opium serves as an indirect indication of the presence of morphia. The two substances are separated by precipitating with lead acetate in presence of acetic acid, and filtering from the lead meconate obtained. The filtrate contains acetate of morphia. If the lead meconate be washed thoroughly and then suspended in water and H S passed through, PbS is precipitated, and meconic acid remains in solution and may be obtained in crystals by evaporation.
133. STRYCHNINE. C21H22N,0, (Strychnos nux vomica and St. Ignatius' bean).
1. Strong pure H2SO4 dissolves strychnine without any discoloration of the solution, even when heated to 100° C. This solution produces certain characteristic colours, with the following reagents :
(a) PbOy, blue coloration, changing to violet, then red, and finally yellow.
(6) K,Cr,Oy, blue coloration, changing soon to yellowish red.
(C) K, Fe(CN), violet coloration, changing less quickly.
(d) MnO2, violet coloration changing to dark red.
2. Strong HNO, dissolves strychnine without discoloration unless heated, when the solution becomes yellow.
3. The taste of strychnine is intensely bitter, and is perceptible even in very dilute solutions.
4. Strychnine, when taken in poisonous doses, produces tetanic convulsions. A most characteristic test, founded on this property, consists in injecting a trace of strychnine under the skin of a young frog, which is soon seized with tetanic convulsions, the body becomes rigid and arched, and the animal soon dies.
134. BRUCINE. C23H26N204 + 4 H2O (Strychnos nux vomica and St. Ignatius' bean).
1. HNO3, when added to brucine, dissolves it, and produces an intense red coloration, which becomes yellow on heating. If SnCl2, Na2S2O3 or (NH4)2S be then added, the colour changes to violet. (Compare corresponding reaction with Morphia, 131, 2.)
135. QUININE. C20H24N202 (Cinchona Bark).
1. Chlorine water, when added to an acid solution of quinine or its salts, produces no coloration until (NH4)HO is added, when a bright green colour is produced. If K4Fe(CN), be added before the (NH)HO, a red coloration is produced, soon changing to dirty brown.
2. KHO or (NH4)HO produces, in solutions of quinine salts, a white amorphous precipitate of quinine, which, on standing, becomes crystalline. The precipitate is scarcely soluble in KHO, but slightly soluble in (NH)HO. If a mixture of a quinine solution and (NH4)HO be shaken up with ether, the precipitated quinine is dissolved. (Compare test 2 for Cinchonine, 136.)
3. Solutions of quinine or its salts are fluorescent in a high degree, and possess an extremely bitter taste.
136. CINCHONINE. C20H24N20 (Cinchona Bark).
1. Chlorine water produces no coloration, even on addition of (NH)HO, which produces a yellowish precipitate.
2. KHO or (NH4)HO produces, in solutions of cinchonine salts, a white aniorphous precipitate of cinchonine, insoluble in excess, and not dissolved when shaken up with ether. (Compare test 2 for Quinine, 135.)
3. Solutions of cinchonine have a bitter taste and an alkaline reaction. The salts are less soluble in water and alcohol than those of quinine.
137. URIC ACID. CH_N403 (Urine).
1. HNO, dissolves uric acid with effervescence, and the solution when evaporated to dryness and moistened with (NH)HO assumes a bright purple colour (murexide).
2. Na,CO2 solution dissolves uric acid. If this solution be placed on paper moistened with AgNO3 solu