POISONS OF VEGETABLE OEIGIN 221 



a million of the resin, freed as much as possible from 

 crystalline matter, killed a roach in fom* hours. The 

 crystals are beautiful white, non-iiitrogenous, crystal- 

 line bodies consisting of carbon, hydrogen and oxygen, 

 with a definite meltmg point at 164 J deg, C, soluble in 

 petrol-ether and chloroform, benzine, toluene, etc., but 

 in water only to the extent of about one in she millions. 

 The pure crystalline form is not very soluble in cold 

 alcohol, and thus it can be separated fi'om the more 

 soluble resinoid part of crude " derrid.'* The crystals 

 (colourless long laminje, with sometimes small hexagonal 

 plates, suggesting that they belong to the rhombic 

 system) are altered and reddened by exposure to even 

 diffused hght, but keep well in the dark ; they are also 

 altered by too long heating with alcohol or other water- 

 containing liquids. The resinoid form melts at about 

 61 deg. C. ; it is rather more soluble in water than the 

 pure crystalHne form. Thus a saturated solution made 

 by exposing the crystals to water for a week or two and 

 then filtered will kill tadpoles when diluted four-fold 

 but not ten-fold, whilst a similar solution made from the 

 resinous residue (which is probably not entirely freed 

 from the crystalUne substance) will kill at ten-fold but 

 not at twenty-fold dilution. The active matter is best 

 extracted from the root by means of petroleum ether 

 or hot paraffin (biuning oil), from which on cooling it 

 separates out as impm-e and resinous canary-coloured 

 masses. From these masses the crystalline body may 

 be purified by extraction and re-crystallisation from 

 alcohol. A characteristic coloiu" reaction is given by 

 both the crystal and the resinoid ** derrid," according 

 to Durham : " treated with a drop of strong nitric acid 

 without heating on a glazed porcelain plate both 

 become red, and then a drop of ammonia causes an 

 evanescent deep rich peacock blue-green (signal green) 



