sucrose vs sugar of milk

sucrose

noun
  • A disaccharide with formula C₁₂H₂₂O₁₁, consisting of two simple sugars, glucose and fructose; normal culinary sugar. 

sugar of milk

noun
  • Lactose, a disaccharide found in milk. 

How often have the words sucrose and sugar of milk occurred in a corpus of books? (source: Google Ngram Viewer )