The analysis of pyrethrum flowers

✍ Scribed by Mitchell, W. M. ;Tresadern, F. H.

• Book ID: 102889626
• Publisher: Wiley (John Wiley & Sons)
• Year: 1949
• Weight: 577 KB
• Volume: 68
• Category: Article
• ISSN: 0368-4075
• DOI: 10.1002/jctb.5000680801

✦ Synopsis

Abstract

It is shown that in the assay of pyrethrum flowers the customary use of warm solvent (soxhlet) gives erroneously high results for pyrethrin II, especially when the higher‐boiling grades of ligroin are used. Cold extraction gives lower results for pyrethrin II, and largely eliminates the variations in the results obtained with different grades of ligroin. It is also shown that cold ligroin extracts all the insecticidally‐active pyrethrins, and that the additional “pyrethrins” extracted by hot ligroin are non‐toxic to house‐flies. Chloroform. is shown to extract a particularly large quantity of such non‐toxic “pyrethrins.” The use of cold ligroin both for the assay, and for the commercial extraction, of pyrethrum flowers is therefore recommended; and it is also suggested that the flowers should be standardized only on their content of pyrethrin I.