Milk Sugar: Whey Boiled to a Fifteenth, Crystallised and Decolourised (US Dispensatory 1907)

Milk is about 5 % milk sugar. The Swiss way of getting it out: curdle the milk with a little dilute sulphuric acid, boil the whey down to a fifteenth of its bulk, and leave it a day or two. The sugar crystallises as a yellow 'sugar-sand', then animal charcoal and recrystallising make it white. Source: The Dispensatory of the United States of America (1907), Saccharum Lactis. Not given: how much acid, and how the sugar-sand is separated and decolourised; those are stated as not given. The vessels, cloth and filter are ours. Picture drawn by Youblob.