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Paragraph 3 Reagents

Original text. Later amendments are not shown.

(1)

Whenever possible, reagents of analytical quality shall be used.

(2)

The buffer-substrate solution shall be prepared as follows:–

(a)

Buffer solution: 3.5 g. of anhydrous sodium carbonate and 1.5 g. of sodium bicarbonate shall be dissolved in distilled or de-ionised water, and made up to one litre.

(b)

Substrate: Disodium p-nitrophenyl phosphate. The solid substrate shall be kept in a refrigerator.

(c)

Buffer-substrate solution: 0.15 g. of the substrate shall be placed in a 100 ml. measuring cylinder, and made up to 100 ml. with the buffer solution. The solution shall be stored in a refrigerator and protected from light. It shall give a reading of less than the standard marked 10 on the comparator disc A.P.T.W. or A.P.T.W.7 when viewed in transmitted light through a 25 mm. cell in the “all-purpose” comparator, distilled or de-ionised water being used for comparison. The solution shall not be used for more than one week.