TntroductionAs long ago as 1846, Liebig and Wohlerl showed that cyanuric acid depolymerizes on being heated to yield isocyanic acid according to equation ( 1 ) : OH -3HNCOHowever, because the HNCO formed is difficult to keep, the investigation of its properties in the intervening years has been fragmentary. Yet HNCO is often formed when compounds containing the amide group (e.g. NH2CONHz2 and NHzCON:NCONH2 3, are heated, as they often are in industrial processes. An understanding of the nature and properties of isocyanic acid is therefore of considerable importance. The purpose of this review is to bring together what is known and not known about this simple and interesting compound. PreparationA. Depolymerization of Cyanuric Acid.-Liebig and Wohler's method,l shown in equation (1) was further developed, to give a purer product and better yield, by Linhard4 and by Herzberg and Reid.5 Cyanuric acid, on being heated, tends to sublime without reaction. In order to achieve depolymerization, heat must first be applied to the solid to vaporize it and then the resulting vapour must be heated still further.Herzberg and Reid5 gave the cyanuric acid a preliminary heating in vacuo to 200°C in order to remove water. The solid was then volatilized slowly in vucuo at 450 "C and the gas stream was passed through a tube furnace at 700 "C. The bulk of the HNCO was collected in a trap at -80°C. After oxidation by

No abstract

No abstract

No abstract

No abstract