Solution to Mohr’s method challenge

Solution to phenylbutazone purity challenge.

In the last 15 years NMR has become a reference technique for the determination of purity for organic standards containing NMR active nuclei [1, 2]. The puzzle proposed for this Analytical Challenge was focused on the use of 1H-NMR for the characterization of a phenylbutazone standard. Such material was purchased from Sigma-Aldrich and analyzed in parallel by HPLC-UV and 1H-NMR. Initially, appl...

Solution to spectroscopy challenge 8.

Malic acid was first isolated by Carl Wilhelm Scheele from apple juice in 1785. Scheele was born in 1742 in Stralsund. The German seaport of Stralsund is situated on the southern coast of a sound of the Baltic Sea that separates the island of Rügen from the mainland. This small town remained under Swedish control until 1815, when it became a part of the Prussian Province of Pomerania. Thus, Sch...

Solution to half-titration challenge.

Solution to the Avogadro constant challenge.

The Avogadro constant has long been defined as the number of molecules of a substance in a gram molecular weight [1]. In a modern parlance, it is a fundamental physical constant representing the number of entities comprising 1 mol. It is clear that any modification to the definition of macroscopic (kilogram) or microscopic mass scales (atomic mass) will affect the numerical value of the Avogadr...

Solution to the whipped egg white challenge.

Since 2001 children in French primary schools have learnt how to make litres of whipped egg white from a single egg, one culinary hand whisk... and their brains [1]. Obviously, the readers of this journal cannot make less! Such a large volume of foam is not too surprising if one considers the content of the whipped egg whites. In short, they are made of water, proteins and air. If the volume st...