from Brown Corpus
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Plane suggested another preparation of Af which we used here.
500 ml of 1M aqueous Af with 1 Af added are heated in a bomb at 170-degrees-C for 48 hours.
A very fine, gray solid ( about 15 g ) is formed, water-washed by centrifugation, and dried at 110-degrees-C ).

1.787 seconds.