Acetylated substances

Place a quantity of the test substance, as specified in the monograph, in a test tube (of maximum 18 mm diameter) and treat it with 3 drops of phosphoric acid (~1440 g/L) TS. Close the tube with a stopper through which passes a smaller test tube filled with water and, on the outside of which, hangs a drop of lanthanum nitrate (30 g/L) TS. Heat the apparatus in a boiling water bath for 5 minutes. Transfer the drop of lanthanum nitrate to a white porcelain spot plate and mix with a drop of iodine (0.02 mol/L) VS. Place at the edge of the mixture a drop of ammonia (~100 g/L) TS. A blue colour slowly appears at the interface of the two liquids and persists for a short time.

Amines, primary aromatic

Dissolve a quantity of the test substance as specified in the monograph in 2 mL of hydrochloric acid (~70 g/L) TS with the aid of heat, if necessary. Cool in ice, treat it with 4 mL of sodium nitrite (10 g/L) TS, allow to stand for 2 minutes and pour the mixture into 2 mL of 2-naphthol TS1 containing 1 g of sodium acetate R. A heavy precipitate, coloured as specified in the monograph, is produced.

Bromides

1. Prepare a solution as specified in the monograph, acidify with nitric acid (~130 g/L) TS and add silver nitrate (40 g/L) TS. A yellowish curdy precipitate is produced, which is partially soluble in ammonia (~260 g/L) TS, but almost insoluble in ammonia (~100 g/L) TS and in nitric acid (~1000 g/L) TS.

2. NOTE: For testing bromides or hydrobromides of insoluble or sparingly soluble bases. Prepare the solution as specified in the monograph, add ammonia (~100 g/L) TS, filter, acidify the filtrate with nitric acid (~130 g/L) TS and proceed with test A.

3. Prepare the solution as specified in the monograph, acidify with sulfuric acid (~100 g/L) TS and mix with chlorine TS. A brown solution results; after shaking with dichloromethane R, it becomes colourless whereas the dichloromethane layer turns reddish.

Calcium

1. Prepare the solution as specified in the monograph and add to it ammonium oxalate (25 g/L) TS. A white precipitate is formed which is soluble in hydrochloric acid (~250 g/L) TS but is practically insoluble in acetic acid (~300 g/L) TS.

2. Treat 1 drop of a solution as specified in the monograph with 4 drops of glyoxal bis(2-hydroxyanil) TS and 1 drop of sodium hydroxide (~80 g/L) TS. A reddish brown precipitate is formed which dissolves in dichloromethane R to give a red solution.

Chlorides

1. Prepare a solution as specified in the monograph, acidify with nitric acid (~130 g/L) TS and add silver nitrate (40 g/L) TS. A white curdy precipitate is produced, which is soluble in ammonia (~100 g/L) TS but is practically insoluble in nitric acid (~1000 g/L) TS.

2. NOTE: For testing chlorides or hydrochlorides of insoluble or sparingly soluble bases. Prepare the solution as specified in the monograph, add ammonia (~100 g/L) TS, filter and acidify the filtrate with nitric acid (~130 g/L) TS and proceed with test A.

3. Mix the quantity of the test substance as specified in the monograph with an equal quantity of manganese dioxide R, moisten with sulfuric acid (~1760 g/L) TS and heat gently. The evolved chlorine is recognizable by its greenish colour and produces a blue coloration of moistened starch/iodide paper R. Carry out the reaction preferably under a hood.

Citrates

1. Treat at ambient temperature a neutral solution as specified in the monograph with calcium chloride (55 g/L) TS. No precipitate is formed but, on boiling, a white solid is produced which is soluble in acetic acid (~300 g/L) TS.

2. Dissolve in 5 mL of water R a quantity of the substance to be examined equivalent to about 50 mg of citric acid or use 5 mL of the prescribed solution. Add 0.5 mL of sulfuric acid R and 1 mL of potassium permanganate (~25 g/L) TS. Warm until the colour of the permanganate is discharged. Add 0.5 mL of a 100 g/L solution of sodium nitroprusside R in dilute sulfuric acid (~98 g/L) TS and 4 g of sulfamic acid R. Make alkaline with concentrated ammonia R, added dropwise until all the sulfamic acid has dissolved. Addition of an excess of ammonia (~260 g/L) TS produces a violet colour, turning to violet-blue.

Ferric salts

Dissolve a quantity of the test substance to be examined equivalent to not less than 1 mg of iron (Fe3+) in 1 mL of water R or use 1 mL of the prescribed solution. Add 1 mL of potassium ferrocyanide (~53 g/L) TS. A blue precipitate is formed that does not dissolve on addition of 5 mL of hydrochloric acid (~70 g/L) TS.

Ferrous salts

1. Prepare a solution as specified in the monograph and add potassium ferricyanide (10 g/L) TS. A dark-blue precipitate is formed which is practically insoluble in hydrochloric acid (~70 g/L) TS.

2. Prepare a solution as specified in the monograph, acidify with sulfuric acid (~100 g/L) TS and treat with o-phenanthroline (1 g/L) TS. An intense red colour is produced which is discharged by the addition of ceric sulfate (35 g/L) TS.

Iodides

1. Prepare a solution as specified in the monograph, acidify with nitric acid (~130 g/L) TS and add silver nitrate (40 g/L) TS. A yellow curdy precipitate is formed which is practically insoluble in ammonia (~100 g/L) TS and in nitric acid (~1000 g/L) TS.

2. NOTE: For testing iodides of insoluble or sparingly soluble bases. Prepare a solution as specified in the monograph, add ammonia (~100 g/L) TS, filter and acidify the filtrate with nitric acid (~130 g/L) TS and proceed with test A.

3. Prepare a solution as specified in the monograph, acidify with sulfuric acid (~100 g/L) TS and add potassium nitrite (100 g/L) TS. A brown solution results; after shaking with dichloromethane R, it becomes colourless whereas the dichloromethane layer turns violet.

Nitrates

1. Prepare a solution as specified in the monograph and treat it with ferrous sulfate (15 g/L) TS. No brown colour appears unless sulfuric acid (~1760 g/L) TS is cautiously added to form a lower layer. A brown colour is then produced at the interface of the two liquids.

2. Add 2 mg of the finely ground test substance to a mixture of 0.1 mL of nitrobenzene R and 0.2 mL of sulfuric acid (~1760 g/L) TS. Allow to stand at room temperature for 5 minutes, cool in ice and add slowly while mixing 5 mL of water and 3 mL of sodium hydroxide (~400 g/L) TS. Add 5 mL of acetone R, shake and allow to separate. An intense violet colour is produced in the upper phase.

Orthophosphates

1. Add, drop by drop, a quantity of nitric acid (~130 g/L) TS to 5 mL of ammonium molybdate (95 g/L) TS until any precipitate that may appear dissolves. Divide this solution into 2 portions, add to one portion the test solution acidified with nitric acid (~130 g/L) TS as specified in the monograph and boil both portions. A yellow precipitate is formed with the test solution while the other shows no more than a slight opalescence.

2. Prepare a neutral solution as specified in the monograph and add silver nitrate (40 g/L) TS. A yellow precipitate is produced which does not darken upon heating the solution to boiling. The precipitate is soluble in ammonia (~100 g/L) TS and in nitric acid (~130 g/L) TS.

Potassium

Prepare an alkaline solution as specified in the monograph and treat it with sodium tetraphenylborate (30 g/L) TS. A white precipitate is produced.

Salicylates

Treat a neutral solution as specified in the monograph with ferric chloride (25 g/L) TS. An intense reddish violet colour appears which remains on the addition of a small amount of acetic acid (~300 g/L) TS but disappears on the addition of hydrochloric acid (~70 g/L) TS, with separation of a white crystalline precipitate.

Sodium

1. Dissolve 0.1 g of the test substance in 2 mL of water R or use 2 mL of the solution described in the monograph. Add 2 mL of potassium carbonate (150 g/L) TS and heat to boiling. No precipitate is formed. Add 4 mL of potassium pyroantimonate (13 g/L) TS and heat to boiling. Allow to cool in iced water and, if necessary, rub the inside of the test tube with a glass rod. A dense white precipitate is produced.

2. Dissolve a quantity of the substance to be examined equivalent to about 2 mg of sodium (Na+) in 0.5 mL of water R or use 0.5 mL of the prescribed solution. Add 1.5 mL of methoxyphenylacetic R and cool in ice-water for 30 minutes. A voluminous, white, crystalline precipitate is produced. Place in water at 20 °C and stir for 5 minutes. The precipitate does not disappear. Add 1 mL of ammonia (~100 g/L) TS. The precipitate dissolves completely. Add 1 mL of ammonium carbonate solution R. No precipitate is produced.

Sulfates

1. Prepare a solution as specified in the monograph and add barium chloride (50 g/L) TS. A white precipitate is formed which is practically insoluble in hydrochloric acid (~250 g/L) TS.

2. To a solution as specified in the monograph, add lead acetate (80 g/L) TS. A white precipitate is formed which is soluble in ammonium acetate (80 g/L) TS and in sodium hydroxide (~80 g/L) TS but practically insoluble in hot water.

Tartrates

1. Acidify a solution as specified in the monograph with acetic acid (~300 g/L) TS and add 1 drop of ferrous sulfate (15 g/L) TS, a few drops of hydrogen peroxide (~60 g/L) TS and enough sodium hydroxide (~80 g/L) TS to make the solution alkaline. A purple or violet colour is produced.

2. Mix a few mL of sulfuric acid (~1760 g/L) TS with a few drops of resorcinol (20 g/L) TS and a few drops of potassium bromide (100 g/L) TS and add 2 or 3 drops of a solution as specified in the monograph. Warm the liquid in a water bath for 5 to 10 minutes. An intense blue colour is produced. Cool the liquid and pour it into water. The solution becomes red.