It has been reported (Bruno Camerino, private communication) that, during the preparation of sodium nitromalonaldehyde monohydrate¹ on a pilot-plant scale, two operators were so affected by the fumes evolved during the preparation that their immediate hospitalization was necessary. It was determined subsequently that hydrogen cyanide, up to approximately 1 g./kg. of mucobromic acid utilized, was formed in the reaction mixture. It is essential that precautions specified in Note 1 of the procedure be followed carefully.