GB459541A - Improvements relating to the manufacture of insecticidal products from pyrethrum flowers - Google Patents

Abstract

The active insecticidal constituents of pyrethrum flowers are obtained by distillation under very high vacuum of about 10<--2> to 10<--6> mm. of mercury and with the distilling and condensing surfaces only about 1 to 5 cm. apart. The dried powdered flowers may be treated directly or may be fed to the still in suspension, or as an extract in a liquid which may be non-volatile, or partly or wholly volatile under the conditions of distillation. When a volatile liquid is used a solution of the active material is obtained directly by the distillation. The liquid may be a linseed oil stand oil, or a mineral oil fraction. According to an example, dried flowers are fed to the apparatus described in Specification 458,119, having the evaporating and condensing surfaces in the form of moving bands, and heated to 180 DEG C. at 10<--4> mm. of mercury, the viscous liquid distillate being scraped from the condensing band. According to a second example, the flowers are extracted at 100 DEG C. with a non-volatile mineral oil known under the Registered Trade Mark "Apiezon J," and the filtered extract is distilled at 170 DEG C. in a high vacuum still of the vertical concentric tube type, such as that described in Specification 437,895. The condenser is maintained at 60 DEG C. so as to obtain a free-flowing distillate.ALSO:The active insecticidal constituents of pyrethrum flowers are obtained by distillation under very high vacuum of about 10-2 to 10-6 mm. of mercury and with the distilling and condensing surfaces only about 1 to 5 cm. apart. The dried powdered flowers may be treated directly or may be fed to the still in suspension, or as an extract, in a liquid which may be non-volatile, or partly or wholly volatile under the conditions of distillation. When a volatile liquid is used, a solution of the active material is obtained directly by the distillation and may be further diluted for use. The liquid may be a linseed oil stand oil, or a mineral oil fraction. According to an example, dried flowers are fed to the apparatus described in Specification 458,119, [Group III], having the evaporating and condensing surfaces in the form of moving bands, and heated to 180 DEG C. at 10-4 mm. of mercury, the viscous liquid distillate being scraped from the condensing band. According to a second example, the flowers are extracted at 100 DEG C. with a non-volatile mineral oil known under the Registered Trade Mark "Apiezon J," and the filtered extract is distilled at 170 DEG C. in a high vacuum still of the vertical concentric tube type, such as that described in Specification 437,895. The condenser is maintained at 60 DEG C. so as to obtain a free-flowing distillate.