Title: General Identification Reactions of Ions and Functional Groups
- Objective: To confirm their identities using chemical Qualitative Tests.
- Principle:
- The process of finding out what compounds are contained in a sample is called Qualitative Analysis.
- Qualitative chemical analysis indicates whether a particular substance is present or not. It does not tell how much of the substance is there or its concentration.
3. Procedure:
The following tests may be used for the identification of chemicals referred to the Pharmacopoeia. They are not intended to be applicable to mixtures of substances unless so specified.
A: Heat the substance being examined with an equal quantity of oxalic acid; acidic vapours with the characteristic odour of acetic acid are liberated.
B: Warm 1 g of the substance being examined with 1 ml of sulphuric acid and 3 ml of ethanol (95%); ethyl acetate, recognisable by its odour, is evolved.
C: Dissolve about 30 mg of the substance being examined in 3 ml of water or use 3 ml of the prescribed solution, add successively 0.25 ml of Lanthanum Nitrate solution, 0.1 ml of 0.1 M Iodine and 0.05 ml of dilute Ammonia solution. Heat carefully to boiling, within a few minutes a blue precipitate or a dark blue colour is produced.
In a test – tube (about 180 mm x 18 mm) place 10 to 20 mg or the prescribed quantity of the substance being examined and add 0.15 ml of Phosphoric acid. Close the tube with a stopper through which passes a small test – tube (about 100 mm x 10 mm) containing water to act as a condenser. On the outside of the smaller tube, hang a drop of Lanthanum Nitrate solution.
Except for substance hydrolysable only with difficulty, place the apparatus in water – bath for 5 minutes and remove the smaller tube. Mix the drop with 0.05 ml of 0.01 M Iodine on a porcelain tile or glass slide and then add one drop of 2M Ammonia at the edge of the mixed drop; after 1 or 2 minutes a blue colour is produced at the junction of the two drops and the colour intensifies and persists for a short time.
For substances hydrolysable only with difficulty, heat the mixture slowly to boiling point over an open flame instead of using a water – bath.
Dissolve a few mg or the prescribed quantity of the substance being examined in 5 ml of water, add dilute Hydrochloric Acid until the solution has an acid reaction and then add 1 ml of Potassium Iodobismuthate solution, an orange or orange – red precipitate is formed immediately.
A: Dissolve about 20 mg of the substance being examined in 2 ml of water or use 2 ml of the prescribed solution, add about 0.5 ml of 2M Hydrochloric Acid and about 0.5 ml of Thioacetamide reagent; no precipitate is produced. Add drop wise 2M Sodium Hydroxide; a gelatinous white precipitate is produced which re dissolves on addition of further 2M Sodium Hydroxide. Gradually add Ammonium Chloride solution; the gelatinous white precipitate reappears.
B: Dissolve about 20 mg of the substance being examined in 5 ml of water or use 5 ml of the prescribed solution, add 5 drops of Ammonium Acetate solution and 5 drops of a 0.1% w/v solution of mordant blue 3; and intense purple colour is produced.
C: To a solution of the substance being examined in water add dilute Ammonia solution until a faint precipitate is produced and then add 0.25 ml of a freshly prepared 0.05 % w/v solution of quinalizarin in a 1 % w/v solution of Sodium Hydroxide. Heat to boiling, cool, and acidify with an excess of acetic acid, a reddish violet colour is produced.
- Amines, primary Aromatic:
Acidify the prescribed solution with 2M Hydrochloric Acid or dissolve 0.1 g of the substance being examined in 2 ml of 2M Hydrochloric Acid and add 0.2 ml of Sodium Nitrite solution. After 1 or 2 minutes add the solution; to 1ml of 2-Naphthol solution; an intense orange or red colour and, usually, a precipitate of the same colour is produced.
A: Heat a few mg of the substance being examined with Sodium Hydroxide solution, Ammonia is evolved, which is recognisable by its odour and by its action on moist red litmus paper, which turns blue.
B: To the prescribed solution add 0.2 g of light Magnesium Oxide. Pass a current of air through the mixture and direct the gas that is evolved to just beneath the surface of a mixture of 1 ml of 0.1M Hydrochloric Acid and 0.05 ml of Methyl Red solution; the colour of the solution changes to yellow. On addition of 1 ml of a freshly prepared 10% w/v solution of Sodium Cobaltinitrite, a yellow precipitate is produced.
Dissolve with gently heating about 10 mg of the substance being examined in a solution of 0.5 g of Sodium Potassium Tartrate in 10 ml of water and allow to cool. To 2 ml of this solution or to 2 ml of the prescribed solution add Sodium Sulphide solution drop wise; a reddish orange precipitate which dissolves on adding dilute Sodium Hydroxide solution is produced.
Heat 5 ml of the prescribed solution on water – bath with an equal volume of hypophosphorus reagent; a brown precipitate is formed.
Dissolve 5 mg of the substance being examined in 3 ml of a hot 0.2% w/v solution of Cobaltous Acetate in methanol, add 5 mg of finely powdered Sodium Tetraborate and boil; a blue – violet colour is produced.
- Barbiturates, Non – nitrogen Substituted:
Dissolve 5 mg of the substance being examined in 3 ml of methanol, add 0.1 ml of a solution containing 10 % w/v of Cobaltous Nitrate and 10% w/v of Calcium Chloride, mix and add, with shaking, 0.1 ml of dilute Sodium Hydroxide solution; a violet – blue colour and a precipitate are produced.
A: Barium salts impart a yellowish green colour to a non – luminous flame which appears blue when viewed through a green glass.
B: Dissolve 20 mg of the substance being examined in 5 ml of dilute hydrochloric acid and add 2 ml of dilute sulphuric acid, a white precipitate, insoluble in nitric acid, is formed.
A: To 1 ml of a 10% w/v neutral solution of the substance being examined add 0.5 ml of ferric chloride test solution; a dull yellow precipitate, soluble in ether, is formed.
B: Moisten 0.2 g of the substance being examined with 0.2 to 0.3 ml of sulphuric acid and gently warm the bottom of the tube; a white sublimate is deposited on the inner walls of the tube and no charring occurs.
C: Dissolve 0.5 g of the substance being examined in 10 ml if water or use 10 ml if the prescribed solution and add 0.5 ml of Hydrochloric Acid, the precipitate obtained, after crystallisation form water and drying at a pressure of 2 kPa, melts at about 122°C.
A: Solutions, when boiled, liberate carbon dioxide.
B: Treat a solution of the substance being examined with a solution of magnesium sulphate; no precipitate is formed. [distinction from carbonates] boil, a white precipitate is formed.
C: Introduce into a test – tube 0.1 g of the substance being examined suspended in 2 ml of water or in 2 ml of the prescribed solution. Add 2 ml of 2M acetic acid, close the tube immediately using a stopper fitted with a glass tube bent at two right – angles, heat gently and collect the gas in 5 ml of Barium Hydroxide solution; a white precipitate forms that dissolves on addition of an excess of dilute Hydrochloric acid.
A: To 0.5 g of the substance being examined add 10 ml of 2M Hydrochloric Acid or us 10 ml of the prescribed solution. Heat to boiling for 1 minute, cool and filter, if necessary. To 1ml of the filtrate add 20 ml of water; a white or slightly yellow precipitate is formed which on addition of 0.05 to 0.1 ml of Sodium Sulphide Solution turns brown.
B: To about 50 mg of the substance being examined add 10 ml of 2M Nitric Acid or use 10 ml of the prescribed solution. Heat to boiling for 1 minute, allow to cool and filter, if necessary. To 5 ml of the filtrate add 2 ml of a 10% w/v solution of thiourea; an orange – yellow colour or an orange precipitate is produced. Add 4 ml of a 2.5% w/v solution of Sodium Fluoride, the solution is not decolorised within 30 minutes.
A: Dissolve a quantity of the substance being examined equivalent to about 3 mg of bromide ion in 2 ml of water or use 2 ml of the prescribed solution. Acidify with 2M Nitric acid, add 1 ml of 0.1M Silver Nitrate, shake and allow to stand; a curdy, pale yellow precipitate forms. Centrifuge and wash the precipitate rapidly with three quantities, each of 1 ml, of water in subdued light. Suspend the precipitate in 2 ml of water and add 1.5 ml of 10 M Ammonia. the precipitate dissolves with difficulty.
B: Dissolve about 10 mg of the substance being examined in 2 ml of water and 1 ml of chlorine solution; bromine is evolved, which is soluble in 2 or 3 drops of Chloroform, forming a reddish solution. To the aqueous solution containing the liberated bromine add phenol solution; a white precipitate is produced.
NOTE: In testing for bromides in the presence of iodides, all iodine must first be removed by boiling the aqueous solution with an excess of lead dioxide.
A: Dissolve 20 mg of the substance being examined in 5 ml of 5M Acetic Acid or add 1 ml of glacial Acetic acid to 5 ml of the prescribed solution. Add 0.5 ml of Potassium Ferrocyanide solution, the solution remains clear. Add about 50mg of Ammonium Chloride; a white, crystalline precipitate is formed.
B: To 5 ml of a 0.4% w/v solution of the substance being examined add 0.2 ml of a 2% w/v solution of Ammonium Oxalate; a white precipitate is obtained that is only sparingly soluble in dilute Acetic Acid but is soluble in Hydrochloric acid.
C: Dissolve 20 mg of the substance being examined in the minimum quantity of dilute Hydrochloric Acid and neutralise with dilute Sodium Hydroxide solution or use 5ml of the prescribed solution. Add 5 ml of Ammonium Carbonate solution; a white precipitate is formed which, after boiling and cooling the mixture, is only sparingly soluble in Ammonium Chloride solution.
A: Suspend 0.1 g of the substance being examined in a test – tube in 2 ml of water or use 2 ml of the prescribed solution. Add 2 ml of 2M Acetic Acid, close the tube immediately using a stopper fitted with a glass tube bent at two right – angles, heat gently and collect the gas in 5 ml of 0.1 M Barium Hydroxide, a white precipitate is formed that dissolves on addition of an excess of dilute Hydrochloric Acid.
B: Treat a solution of the substance being examined with a solution of Magnesium Sulphate; a white precipitate is formed (distinction from bicarbonates).
A: Dissolve a quantity of the substance being examined equivalent to about 2 mg of chloride ion in 2 ml of water or use 2 ml of the prescribed solution. Acidify with dilute Nitric Acid, add 0.5 ml of Silver Nitrate solution, shake and allow to stand, a curdy white precipitate is formed, which is insoluble in Nitric Acid but soluble, after being well washed with water, in Dilute Ammonia solution, from which is insoluble in Nitric Acid but soluble, after being well washed with water, in dilute Ammonia solution, from which it is reprecipitated by the addition of dilute Nitric acid.
B: Introduce into a test-tube a quantity of the substance being examined equivalent to about 10 mg of chloride ion, add 0.2 g of Potassium Dichromate and 1 ml of Sulphuric Acid. Place a filter-paper strip moistened with 0.1 ml of Diphenylcarbazide solution over the mouth of the test-tube; the paper turns violet-red.(Do not bring the moistened paper into contact with the Potassium Dichromate solution).
A: To a neutral solution of the substance being examined add a solution of calcium chloride; no precipitate is produced. Boil the solution; a white precipitate soluble in 6M acetic acid is produced.
B: Dissolve a quantity of the substance being examined equivalent to about 50 mg of Citric Acid in 5 ml of water or use 5 ml of the prescribed solution. Add 0.5 ml of Sulphuric Acid and 3 ml of Potassium Permanganate solution. Warm until the colour of the permanganate is discharged and add 0.5 ml of a 10% w/v solution of Sodium Nitroprusside in 1M Sulphuric Acid and 4 g of Sulphamic Acid. Make alkaline with strong Ammonia solution, added drop wise until all the Sulphamic Acid has dissolved. On addition of an excess of strong ammonia solution a violet colour, which turn violet-blue, is produced.
To about 30 mg. of the substance being examined or to the prescribed quantity add 0.5 ml of a 7% w/v solution of Hydroxylamine Hydrochloride in methanol and 0.5 ml of a 10% w/v solution of Potassium Hydroxide in ethanol (95 %). Heat to boiling, cool,acidify with 2M Hydrochloric Acid and add 0.2 ml of a 1% w/v solution of Ferric Chloride; a bluish red or red colour is produced.
A: Dissolve a quantity of the substance being examined equivalent to about 10 mg of iron in 1 ml of water or use 1 ml of the prescribed solution. Add 1 ml of Potassium Ferrocyanide solution; an intense blue precipitate, insoluble in dilute Hydrochloric acid, is produced.
B: To 3 ml of solution containing about 0.1 mg of iron or to 3 ml of the prescribed solution add 1 ml of 2M Hydrochloric Acid and 1 ml of Ammonium Thiocyanate solution; the solution becomes blood-red in colour. Take two portions, each of 1 ml, of the mixture. To one portion add 5 ml of ether, shake and allow to stand; the ether layer is pink. To the other portion add 3 ml of 0.2M Mercuric Chloride; the red colour disappears.
C: To 2 ml of solution containing about 0.1 mg of iron or to 3 ml of the prescribed solution add Acetic Acid until the solution is strongly acidic. Add 2 ml of a 0.2 % w/v solution of 8-hydroxy-7-Iodoquinoline –5– Sulphonic acid; a stable green colour is produced.
A: Dissolve a quantity of the substance being examined equivalent to about 10 mg of iron in 2 ml of water or use 2 ml of the prescribed solution. Add 2 ml of dilute Sulphuric Acid and 1 ml of 0.1 % w/v solution of 1,10-Phenanthroline; an intense red colour which is discharged by addition of a slight excess of 0.1 M Ceric Ammonium Sulphate is produced.
B: To 1 ml of a solution containing not less than 1 mg of iron or to 1 ml of the prescribed solution add 1 ml of Potassium Ferricyanide solution; a dark blue precipitate is formed that is insoluble in dilute Hydrochloric Acid and is decomposed by Sodium Hydroxide solution.
C: To 1 ml of a solution containing not less than 1 mg of iron or to 1 ml of the prescribed solution add 1 ml of Potassium Ferrocyanide solution; a white precipitate is formed which rapidly becomes blue and is insoluble in dilute Hydrochloric acid.
A: Dissolve a quantity of the substance being examined equivalent to about 4 mg of iodide ion in 2 ml of water or use 2 ml of the prescribed solution. Acidify with dilute nitric acid and add 0.5 ml of Silver Nitrate solution. Shake and allow to stand; a curdy, pale yellow precipitate is formed. Centrifuge and wash the precipitate rapidly with three quantities, each of 1 ml, of water, in subdued light. Suspend the precipitate in 2 ml of water and add 1.5 ml of 10M Ammonia; the precipitate does not dissolve.
B: To 0.2 ml of solution of the substance being examined containing the equivalent of about 5 mg of iodide ion per ml or to 0.2 ml of the prescribed solution add 0.5 ml of 1M Sulphuric acid, 0.15 ml of Potassium Dichromate solution, 2 ml of water and 2 ml of chloroform shake for few seconds and allow to stand ; the chloroform layer is violet or violet-red.
C: To 1 ml of a solution of the substance being examined containing the equivalent of about 5 mg of iodide ion add 0.5 ml of Mercuric Chloride solution; a dark red precipitate is formed which is slightly soluble in an excess of this reagent and very soluble in an excess of Potassium Iodide solution.
To 5 ml of a solution of the substance being examined containing the equivalent of about 5 mg of Lactic Acid or to 5 ml of the prescribed solution add 1 ml of bromine water and 0.5 ml of 1M Sulphuric Acid. Heat on a water-bath, stirring occasionally with a glass rod until the colour is discharged. Add 4 g of Ammonium Sulphate, mix and add dropwise, without mixing, 0.2 ml of a 10 % w/v solution of Sodium Nitroprusside in 1M Sulphuric Acid. Without mixing, add 1 ml of strong Ammonia solution and allow to stand for 30 minutes; a dark green ring appears at the interface of the two liquids.
A: Dissolve 0.1 g of the substance being examined in 1 ml of dilute Acetic acid or use 1ml of the prescribed solution. Add 2 ml of Potassium Chromate solution; a yellow precipitate insoluble in 2 ml of 10M Sodium Hydroxide is produced.
B: Dissolve 50 mg of the substance being examined in 1 ml of dilute acetic acid or use 1 ml of the prescribed solution. Add 10 ml of water and 0.2 ml of 1M Potassium Iodide; a yellow precipitate is formed. Heat to boiling for 1 or 2 minutes and allow to cool; the precipitate is reformed as glistening, yellow plates.
A: Dissolve about 15 mg of the substance being examined in 2 ml of water or use 2 ml of the prescribed solution. Add 1 ml of dilute Ammonia solution; a white precipitate forms that is redissolved by adding 1 ml of 2M Ammonium Chloride. Add 1 ml of 0.25 M Disodium Hydrogen Phosphate; a white crystalline precipitate is produced.
B: To 0.5 ml of a neutral or slightly acid solution of the substance being examined add 0.2 ml of a 0.1 % w/v solution of titan yellow and 0.5 ml of 0.1 M Sodium Hydroxide; a bright red turbidity develops which gradually settles to give a bright red precipitate.
A: Place 0.05 to 0.1 ml of a solution of the substance being examined on well-scraped copper foil; a dark gray stain, which becomes shiny on rubbing, is produced. Heat the dried copper foil in a test-tube; the spot disappears.
B: To a solution of the substance being examined add carefully Potassium Iodide solution; a red precipitate is produced which is soluble in an excess of the reagent (mercuric compounds) or a yellow precipitate is produced which may become green on standing (mercurous compounds).
C: To the prescribed solution add 2M Sodium Hydroxide until strongly alkaline; a dense, yellow precipitate is produced (mercuric compounds).
D: To a solution of the substance being examined add 6 M Hydrochloric Acid; a white precipitate is produced which is blackened by adding dilute Ammonia solution (mercurous compounds).
A: Dissolve 15 mg of the substance being examined in 0.5 ml of water, add cautiously 1ml of Sulphuric Acid, mix and cool. Incline the tube and carefully add, without mixing, 0.5 ml of Ferrous Sulphate solution; a brown colour is produced at the interface of the two liquids.
B: To a mixture of 0.1 ml of nitrobenzene and 0.2 ml of Sulphuric Acid add a quantity of the powdered substance being examined equivalent to about 1 mg of nitrate ion or the prescribed quantity. Allow to stand for 5 minutes and cool in ice whilst adding slowly with stirring 5 ml of water and then 5 ml of Sodium Hydroxide solution. Add 5 ml of Acetone, shake and allow to stand; the upper layer shows an intense violet colour.
To 2 mg of the substance being examined add 2 mg of Chromotropic acid Sodium Salt and 2 ml Sulphuric Acid and immerse in an oil-bath at 150° ; the solution, when shaken and examined every 30 seconds, exhibits the colours stated in Table 1.
- Penicillins and Cephalosporins:
Carry out Tests A and B unless otherwise stated in the monograph.
A: Place 2 mg of the substance being examined in a test-tube (about 15 cm x 15 mm), moisten with 0.05 ml of water and add 2 ml of Sulphuric acid (95 % w/w). Mix the contents of the tube by swirling and examine the colour of the solution. Immerse the test-tube in a water-bath for 1 minute and examine the colour again. The solution exhibit the colours stated in columns 2 and 3 of Table 2.
B: Carry out the procedure described in Test A using 2 ml of a mixture of 2 ml of formaldehyde solution and 100 ml of Sulphuric acid (95 % w/w) in place of the Sulphuric acid (96 % w/w). The solution exhibit the colours stated in columns 4 and 5 of Table 2.
TABLE 1
| Time
(min) |
Ampicillin,Ampicillin
Sodium, Ampicillin
Trihydrate |
Benzathine,
Penicillin,
Benzylpenicillin Potassium/ Sodium |
Carbenicillin
Sodium |
Cloxacillin Sodium |
Phenoxyme- thylpenicillin Potassium |
| 0 |
Colourless |
Yellow |
Colourless |
Colourless |
Colourless |
| 0.5 |
Colourless |
Yellow |
Light brown |
Pale yellow |
Colourless |
| 1 |
Colourless |
yellow |
Yellowish brown |
Greenish yellow |
Colourless |
| 1.5 |
Colourless |
Orange yellow |
Greenish brown |
Yellowish green |
Pale pink
|
| 2 |
Purple |
Orange yellow |
Greenish brown |
Green |
Purple |
| 2.5 |
Deep purple |
Orange yellow |
Brown |
Greenish purple |
Purple |
| 3 |
Violet |
Pale Orange |
Dark brown |
Purple |
Bluish violet |
| 3.5 |
Violet |
Orange or may char |
Dark brown |
Purple |
Dark blue |
| 4 |
Charred |
– |
– |
– |
– |
TABLE 2
| Substance
(1) |
Sulphuric acid
(95 per cent w/w)
(2) |
Sulphuric acid (95 % w/w) after 1 minute at 100°
(3) |
Formaldehyde solution and Sulphuric acid
(95 % w/w)
(4) |
Formaldehyde solution and sulphuric acid (95 % w/w ) after 1 minute at 100°
(5) |
| Amoxycillin Trihydrate |
|
|
Almost colourless |
Dark yellow |
| Ampicillin |
|
|
Almost colourless |
Dark yellow |
| Ampicillin Sodium |
|
|
Almost colourless |
Dark yellow |
| Ampicillin Trihydrate |
|
|
Almost colourless |
Dark yellow |
| Benzathine Penicillin |
|
|
Almost colourless |
Reddish brown |
| Benzyl penicillin Potassium |
|
|
|
Reddish brown |
| Benzyl penicillin Sodium |
|
|
Almost colourless |
Reddish brown |
| Carbenicillin Sodium |
|
|
Almost colourless |
Yellowish brown |
| Cephalexin |
Almost colourless |
Pale yellow |
Pale yellow |
Yellow |
| Cefadroxil |
|
|
Yellow |
Orange |
| Cephaloridine |
Pale yellow |
Almost colourless |
Red |
Brownish red |
| Cloxacillin Sodium |
|
|
Slightly greenish yellow |
Yellow |
| Phenoxymethyl Penicillin Potassium |
|
|
Reddish brown |
Dark Reddish brown |
| Procaine Penicillin |
Almost colourless |
Almost colourless |
Almost colourless |
Reddish Brown |
- Phosphates (Orthophosphates):
A: To 5 ml of the prescribed solution, neutralised to pH 7.0, add 5 ml of Silver Nitrate solution; a light yellow precipitate forms, the colour of which is not changed by boiling and which is readily soluble in 10 M Ammonia and in dilute Nitric acid.
B: Mix 1 ml of the prescribed solution with 1 ml of Ammoniacal Magnesium Sulphate solution; a white crystalline precipitate is formed.
C: To 2 ml of the prescribed solution and 2 ml of dilute Nitric Acid and 4 ml of Ammonium Molybdate solution and warm the solution; a bright yellow precipitate is formed.
A: Dissolve about 50 mg of the substance being examined in 1 ml of water or use 1 ml of the prescribed solution. Add 1 ml of dilute Acetic Acid and 1 ml of a freshly prepared 10 % w/v solution of Sodium Cobaltinitrite; a yellow or orange-yellow precipitate is produced immediately.
B: Dissolve 0.1 g of the substance being examined in 2 ml of water or use 2 ml of the prescribed solution. Heat the solution with 1 ml of Sodium Carbonate solution; no precipitate is formed. Add 0.05 ml of Sodium Sulphide solution; no precipitate is formed. Cool in ice, add 2 ml of a 15% w/v solution of Tartaric Acid and allow to stand; a white, crystalline precipitate is produced.
C: Ignite a few mg of the substance being examined, cool and dissolve in the minimum quantity of water. To this solution add 1 ml of Platinic Chloride solution in the presence of 1 ml of Hydrochloric acid; a yellow, crystalline precipitate is produced which on ignition leaves a residue of Potassium Chloride and Platinum.
A: To 1 ml of a 10 % w/v neutral solution add 0.5 ml of Ferric Chloride test solution; a violet colour is produced which persists after the addition of 0.1 ml of dilute Acetic Acid.
B: Dissolve 0.5 g of the substance being examined in 10 ml of water or use 10 ml of the prescribed solution. Add 0.5 ml of Hydrochloric Acid; the precipitate obtained after recrystallisation from hot water and drying at a pressure of 2 kPa melts at about 159°C.
C: Dissolve 0.5 g of the substance being examined in 10 ml of water or use 10 ml of the prescribed solution. Add 2 ml of bromine solution; a cream-coloured precipitate is formed.
In a lead or platinum crucible mix by means of a copper wire to obtain a thin slurry the prescribed quantity of the substance being examined with 10 mg of Sodium Fluoride and a few drops of Sulphuric Acid. Cover the crucible with a thin transparent plate of plastic under which a drop of water is suspended and warm gently; within a short time a white ring is formed around the drop of water.
Dissolve 10 mg of the substance being examined in 10 ml of water or use 10 ml of the prescribed solution. Add 0.3 ml of dilute Hydrochloric Acid; a curdy white precipitate, soluble in dilute Ammonia solution, is produced. Add Potassium Iodide solution; a yellow precipitate, soluble in Nitric Acid, is produced.
A: Dissolve 0.1 g of the substance being examined in 2 ml of water or use 2 ml of the prescribed solution. Add 2 ml of a 15% w/v solution of Potassium Carbonate and heat to boiling; no precipitate is produced. Add 4 ml of a freshly prepared Potassium Antimonate solution and heat to boiling. Allow to cool in ice and if necessary scratch the inside of the test-tube with a glass rod; a dense, white precipitate is formed.
B: Dissolve a quantity of substance being examined equivalen to about 2 mg of Sodium (Na+) in 0.5 ml of water or use 0.5 ml prescribed solution. Add 1.5 ml of Methoxyphenylacetic acid reagent and cool it in ice water bath for 30 minutes, A voluminous, white crystalline precipitate is formed. Place in water for 20° and stir for 15 minutes. The precipitate does not disappear. Add 1 ml f dilute Ammonium Carbonate solution. No precipitate is formed.
A: Dissolve about 50 mg of the substance being examined in 5 ml of water or use 5 ml of the prescribed solution. Add 1 ml of dilute Hydrochloric Acid and 1 ml of Barium Chloride solution; a white precipitate is formed.
B: Add 0.1 ml of iodine solution to the suspension obtained in test A; the suspension remains yellow (distinction from sulphites and dithionites) but is decolourised by adding, drop wise, Stannous Chloride solution (distinction from iodates). Boil the mixture; no coloured precipitate is formed (distinction from selenates and tungstates).
C: Dissolve about 50 mg of the substance being examined in 5 ml of water or use 5 ml of the prescribed solution. Add 2 ml of Lead Acetate solution; a white precipitate, soluble in Ammonium Acetate solution and in Sodium Hydroxide solution, is produced.
- Sulphur in Organic Compounds:
A: Burn about 20 mg of the substance being examined by the oxygen-flask method, using 15 ml of water and 2 ml of Hydrogen Peroxide solution (10 vol.) as the absorbing liquid. When combustion is complete, boil the solution gently for 10 minutes, adding water if necessary, and cool. The resulting solution gives the reactions of sulphates.
B: To about 50 mg of the substance being examined add 0.25 g of Zinc and Sodium Carbonate reagent, mix and transfer to a small, thin-walled test-tube of hard glass and cover with a layer of the reagent. Carefully heat the tube to red heat, starting at the upper end and heating towards the bottom, then drop the tube immediately into about 20 ml of water. Filter and acidify the filtrate with Hydrochloric Acid; fumes which stain lead acetate paper brown or black are evolved.
A: Warm the substance being examined with Sulphuric Acid; charring occurs and carbon monoxide, which burns with a blue flame when ignited, is evolved.
B: Dissolve about 20 mg of the substance being examined in 5 ml of water or use 5 ml of the prescribed solution. Add 0.05 ml of a 1 % w/v solution of Ferrous Sulphate and 0.05 ml of Hydrogen Peroxide solution (10 vol.); a transient yellow colour is produced. After the colour has disappeared add 2M Sodium Hydroxide drop wise; an intense blue colour is produced.
C: Heat 0.1 ml of solution containing the equivalent of about 2 mg of Tartric acid or 0.1 ml of prescribed solution on a water-bath for 5 to 10 minutes with 0.1 ml of a 10% w/v solution of Potassium Bromide, 0.1 ml of 2 % w/v solution of resorcinol and 3 ml of Sulphuric acid; a dark blue colour that changes to red when the solution is cooled and poured into water is produced.
A: Dissolve 0.1 g of the substance being examined in 5 ml of water and add 2 ml of Hydrochloric Acid; a white precipitate is formed which soon turns yellow and Sulphur dioxide, recognisable by its odour, is evolved.
B: Dissolve 0.1 g of the substance being examined in 5 ml of water and add 2 ml of Ferric Chloride test solution; a dark violet colour which quickly disappears is produced.
C: Solutions of Thiosulphates decolorized iodine solution; the decolourised solutions do not give the reactions of sulphates.
D: Solutions of Thiosulphates decolorize bromine solution; the decolorized solutions give the reactions of sulphates.
Mix a few mg of the substance being examined or the prescribed quantity with 0.1 ml of Hydrogen Peroxide solution (100 vol.) and 0.3 ml of 2M Hydrochloric Acid, heat to dryness on a water-bath until a yellowish red residue is produced and add 0.1 ml of 2M Ammonia; the colour of the residue changes to reddish violet.
A: Dissolve 0.1 g of the substance being examined in 5 ml of water or use 5 ml of the prescribed solution. Add 0.2 ml of Sodium Hydroxide solution; a white precipitate is produced. Add a further 2 ml of Sodium Hydroxide solution; the precipitate dissolves. Add 10 ml of Ammonium Chloride solution; the solution remains clear. Add 0.1 ml of Sodium Sulphide solution; a flocculent, white precipitate is produced.
B: Dissolve 0.1 g of the substance being examined in 5 ml of water or use 5 ml of the prescribed solution. Acidify with dilute Sulphuric Aacid and add one drop of a 0.1 % w/v solution of Cupric Sulphate and 2 ml of Ammonium Mercury thiocyanate solution; a violet precipitate is formed.
C: Dissolve 0.1 g of the substance being examined in 5 ml of water or use 5 ml of the prescribed solution. Add 2 ml of Potassium Ferrocyanide solution; a white precipitate, insoluble in dilutes Hydrochloric Acid, is produced.
“End of Document”
