This salt, on standing, decomposes into barium dithionate, BaS206, and diethyl disulphide, (C2H5)2S2, which points to the presence of the SH group in the molecule.
Many esters of malonic acid have been prepared, the most important being the diethyl ester (malonic ester), CH 2 (000C 2 H 5) 2, which is obtained by dissolving monochloracetic acid in water, neutralizing the solution with potassium carbonate, and then adding potassium cyanide and warming the mixture until the reaction begins.
It is a colourless oily liquid of strongly acid reaction; its aqueous solution decomposes on standing and on heating it forms diethyl sulphate and sulphuric acid.
Great care should be taken in using dimethyl and diethyl sulphates, as the respiratory organs are affected by the vapours, leading to severe attacks of pneumonia.
Veronal (q.v.) is diethyl malonyl urea.