How to visualize the different lactose content of dairy products by Fearon’s test and Woehlk test in classroom experiments and a new approach to the mechanisms and formulae of the mysterious red dyes

Abstract

The article connects historical developments in analytics with contexts of today and school experiments: Woehlk test and Fearon’s test are historically known as the reactions of lactose and maltose with ammonia and methylamine, respectively. Both lead to characteristic red dyes whose formation and structural formulae had not been of interest or had even been reported incorrectly until 2015. Even though these tests, developed in the first half of the twentieth century, are obsolete in medicinal analysis today, they pose interesting experiments for school chemistry, when investigating the topic of macromolecules or sugars. In an inquiry or context-based teaching approach, tests visualizing different lactose concentrations in different dairy products would fit into the contexts milk and chemical detection of diseases. The experiments can also be used in a historically based problem-oriented approach in which the scientists, their work and lives can be the central perspective. As both methods of analysis result in brightly colored solutions, they are easily interpretable as well as aesthetically appealing to students. As the test developed by Fearon is quicker and makes use of less dangerous chemicals, it is the one to be preferably used in school.

Keywords

• dairy products
• detection reaction
• fearon
• history of medicine and chemistry
• lactose
• life sciences
• mechanism
• school experiment
• woehlk