127. FERRI-CYANIC ACID. H,Fe(CN)6

1. AgNO, produces an orange-coloured precipitate of Ag,Fe(CN)6, insoluble in dilute HNO3, soluble in (NH4)HO and KCN.

*2. FeSO4 produces a blue precipitate of Fe,Fe(CN)12 (Turnbull's blue), insoluble in acids, but decomposed by alkalies.

3. FeCl produces no precipitate, but alters the colour to a greenish brown.

127a. SULPHO-CYANIC ACID. H(CN)S.

1. AgNO, produces a white curdy precipitate of Ag(CN)S insoluble in dilute acids but soluble in (NH)HO, and in solution of K(CN)S. From the solution in (NH)HO it crystalizes in shining scales.

2. CuSO4 produces in strong solutions a black crystalline precipitate of Cu(CN)2S, which changes on standing to the cuprous salt Cu2(CN)2S, which is white. This change takes place at once by the addition of reducing agents (e.g. SO, or FeSO4) to the cupric salt. *3. FeCl produces a blood-red coloration from formation of a soluble sulpho-cyanate of iron. The colour is destroyed by addition of alkalies, by HgCl, and by many acids (e.g. HNO3, H3PO4, H2C2O4 HIO3), but not by HCl even when concentrated.

128. ACETIC ACID. C2H4O2.

1. AgNO, produces, in neutral solutions, a white crystalline precipitate of C2H,AgO soluble in (NH)HO and in hot water.

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2. Fe,Cl, 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 H2So, and alcohol yields acetic ether, recognized by its characteristic and pleasant odour.

129. FORMIC ACID. CH2O2.

1. AgNO, produces, in neutral concentrated solutions, a white precipitate of CHAgO,, which rapidly darkens, especially on heating, owing to separation of Ag.

2. FeCl produces a similar reaction with formates as with acetates.

*3. Hg(NO3)2 produces a white precipitate of the formate of mercury, which, however, soon becomes grey from separation of Hg.

*4. Cold strong H,SO, decomposes formates with effervescence, CO being evolved. On heating, the gas comes off rapidly, and if lighted, burns with a blue

flame.

130. Higher fatty acid.

STEARIC ACID. C18H3602.

1. Heated with alkalies, a soap is formed. If mutton fat (which contains the acid combined with glycerine) be heated 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. 130a. CARBOLIC ACID OR PHENOL. CH,(HO). 1. Bromine water gives a yellowish white precipitate (Tribromo-phenol) even in dilute solutions.

2. Ferric chloride produces a violet coloration.

3. Heated with ammonia and a drop of sodium hypochlorite, a deep blue colour is produced, which becomes red on addition of acids.

130b. SALICYLIC ACID. C,H6O3.

I. Heated with lime, phenol is evolved, easily recognized by its smell (like tar).

2. Ferric chloride produces even in very dilute solutions a deep violet colour, which disappears on addition of acids or alkalies.

3. Bromine water gives a white precipitate. (Compare 130a I.)

TESTS FOR ORGANIC ALKALOIDS AND CERTAIN OTHER ORGANIC BODIES.

131. MORPHINE. C17H19 NO3 (Opium).*

1. KHO and (NH4)HO precipitate morphia from its salts, readily soluble in excess of KHO, less readily in excess of (NH1)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 SnCl2 or of Na2SO ̧ destroys the colour.

3. A neutral solution of Fe,Cl, produces, when added to morphia (either in the dry state or in solution), a deep blue colour.

4. HIC, when added either to free or combined morphia, is decomposed with liberation of I, which colours the liquid brown. Starched paper added to the solution becomes blue. Addition of (NH)HO deepens the brown colour.

5. H2SO4 produces no coloration with morphia or its salts, but on adding a crystal of K,Cr,O, a bright green colour is produced.

132. MECONIC ACID, CH4O7 (Opium).

1. FeCl 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. are derived.

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 FeCl 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 H2S passed through, PbS is precipitated, and meconic acid remains in solution and may be obtained in crystals by evaporation.

133. STRYCHNINE.

C21H22N2O2 (Strychnos nux

vomica and St. Ignatius' bean).

I. 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) PbO2, blue coloration, changing to violet, then red, and finally yellow.

(b) K2Cr2O7, blue coloration, changing soon to yellowish red.

(c) K4Fe(CN), violet coloration, changing less quickly.

(d) MnO, violet coloration changing to dark red. 2. Strong HNO3 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.

C23H26N2O4+ 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, Na,S,O, or (NH4)2S be then added, the colour changes to violet. (Compare corresponding reaction with Morphia, 131, 2.)

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135. QUININE. CH2N2O, (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 (NH1)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,