Does lactose give a positive Seliwanoff test?

No, lactose does not give a positive Seliwanoff test. Lactose is a disaccharide composed of glucose and galactose, both of which are aldose sugars. Since the Seliwanoff test specifically detects ketoses, lactose, being composed of aldose sugars, does not react with resorcinol to produce the characteristic red color, and thus gives a negative result.