Direct Analysis of Lactose in Milk and Serum

showed that the colorimetric phenol-sulfuric acid method of Dubois et al. (2) could be used for the direct determination of lactose in milk and cheese. The authors stated that the amount of phenol added was not critical, provided that the same quantity was used throughout. However, variations which occurred in our replicate analyses of standard lactose solutions were traced to minute differenees in the amount of phenol reagent added.