Solution to highest melting point challenge

Prediction of the material with highest known melting point from ab initio molecular dynamics calculations

Using electronic structure calculations, we conduct an extensive investigation into the Hf-Ta-C system, which includes the compounds that have the highest melting points known to date. We identify three major chemical factors that contribute to the high melting temperatures. Based on these factors, we propose a class of materials that may possess even higher melting temperatures and explore it ...

Melting Point Determination

An improved technique is described for the accurate determination of melting points of metals in the temperature range 1500° to 2500°C. The improvements consist of gradient heating and refinements in cavity preparation to obtain true black-body conditions. The melting point of hafnium, as determined by this method, is set a t 22220-+30°C. This is over 200°C higher than one of the values reporte...

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.