Factors affecting the recovery of hydrocyanic acid from fumigated citrus tissues

does not appear. First page follows. Under certain conditions of fumigation for scale insects of citrus trees, hydrocyanic acid (HCN) is known to cause injury to the foliage and fruit. The physiological reactions involved in the injury have received but slight quantitative investigation. Undoubtedly the reasons for this have been the difficulties encountered in distilling HCN from materials containing volatile substances which are reactive with HCN. The lack of a method with sufficient accuracy to recover relatively small amounts of HCN from the tissues may also have been an important factor. The results reported in this paper are concerned only with the factors affecting the distillation and recovery of HCN from solutions in the absence of tissues and also in the presence of citrus foliage and fruits. Earlier attempts to recover HCN from fumigated citrus tissues by aspiration, partial vacuum, immersing and shaking the tissues in an alkaline solution, or by a combination of these processes have given unsatisfactory results. All statements in this paper concerning the recovery of HCN from citrus tissues refer to HCN added by fumigation or by other methods. Repeated tests by Bartholomew and Raby (3) and in the present investigation have shown that citrus tissues do not contain autogenous HCN. An investigation is being made of the physiological effects of HCN in citrus tissues.