The determination of the factor for pyrethrin 1 in the mercury method

The authors have examined in two series of experiments the effect of varying the conditions under which the reduction of Denigès reagent by chrysanthemum monocarboxylic acid is allowed to proceed. They have shown that both temperature and time of reaction influence appreciably the extent of the reduction; and have confirmed the result previously obtained by Graham and LaForge, that 1 ml. 0·01 M-potassium iodate solution is equivalent to 5·7 mg. pyrethrin 1 when the reduction takes place, at 25 ± 2° for 1 hour. Differences of 5—6% of the general mean value were shown in the second series despite careful standardisation of conditions. RESP-2664