manual of methods of analysis of foods - Ministry of Health and ...

METALS
solution being buffered to pH 3.8. The absorption maximum of the resulting
complex is 555 nm.
Reagents:
(a) Sulphuric acid (Sp. Gr. 1.84)
(b) Nitric acid (Sp. Gr. 1.40)
(c) Perchloric acid (Sp. Gr. 1.67)
(d) Hydrogen peroxide (30%)
(e) Hydrochloric acid solution: (Approximately 5M)
Dilute 107 ml of HCl (Sp. Gr. 1.18) to 250 ml with water.
(f)
(g)
(h)
Sulphuric acid solution: (Approximately 4.5M)
Dilute 250 ml of H 2 SO 4 (a) to 1000 ml with water.
Potassium iodide solution: (Approximately 5M):
Dissolve 83 g KI in 100 ml water. Prepare fresh daily.
Sodium hydroxide solutions:
Prepare fresh each fortnight:
(i)
Approximately 5M solution: Dissolve 100 g of NaOH in water
and dilute to 500 ml.
(ii)
Approximately 0.1M solution: Dissolve 2 g of NaOH in water
and dilute to 500 ml.
(i) Ascorbic acid solution: (5% w / v)
Dissolve 1 g of ascorbic acid in 20 ml of water. Prepare fresh daily.
(j)
Catechol violet solution: (0.025% w/v)
Dissolve 25 mg of catechol violet in a mixture of equal part of ethanol
and water to produce 100 ml and mix. Prepare fresh daily.
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