A colorimetric determination of hydrocyanic acid

The object of this investigation is to devise a rapid, fairly accurate, colorimetric analysis for HCN to be used in field work for determining instantaneous concentrations of the gas under fumigating canvas. A large amount of money is expended yearly by the citrus industry of this state in attempting to control and to eradicate the scale pests. Although fumigation with HCN has been practiced tor many years, the progress made has been anything but satisfactory. The greater portion of the work has always been carried on by contractors, who in a large number of cases have been very unscrupulous. The materials and labor are very expensive and the growers have been satisfied to adhere to beaten paths and hope for the best results on scale kill with the least attendant foliage injury. One familiar with fumigating, either from the grower's or the operator's viewpoint, knows that very widely varying results are obtained, even under what are apparently identical condition. Even after discounting for the dishonesty of some operators and the prejudices of the grower, there is still a large variance between desired or expected results and those actually obtained.