Acid Formation
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The solution from (b) above is cooled to —10C and during 50 min (1) 122 Kg. of 78% sulphuric acid diluted to 600 litres, (2) 200 Kg. 60% sodium dichromate solution diluted to 800 litres and 660 Kg. of 45% sodium thiosulphate are added in four portion (1/4, 1/4 1/8 and 3/8 of each). The final temperature should be 10C. The contents are agitated for 1 hour and the temperature adjusted to 30C.
