Sept. 3, 1917 



Quassia Extract as a Contact Insecticide 



503 



extracted a number of times, and an effective extract obtained in each 

 case. Consequently 10 gm. of medium-sized chips were extracted for 2 

 hours with 500 c. c. of distilled water. This mixture was then filtered 

 and the filtrate evaporated to determine the quantity of extract obtained. 

 The same chips were extracted successively six times by using the same 

 amount of fresh distilled water each time, and the quantity of extract was 

 determined after each extraction. The experiment was then repeated, 

 the time of extraction in each case being 24, instead of 2 hours. The 

 results are presented in Table I. In this and the other tables the quan- 

 tity of extract does not necessarily mean the quantity of quassiin. 



Tabi,E I. — Quantity and percentage of extract dissolved by successive extractions of 10 gm. 

 of quassia chips with §00 c. c. of distilled water for 2 and 24 hours, respectively 



It will be noted that after five extractions of two hours each, prac- 

 tically nothing further is extracted. The total extract in the five por- 

 tions of 500 c. c. each is 0.1730 gm. When the chips were extracted 

 for 24 hours, the total extract in the five portions of 500 c. c. each was 

 0.2309 gm., or 0.0579 g^- more than in the first case. It is evident from 

 this that a relatively long period of soaking is essential in order to get 

 the maximum quantity of quassiin in solution. It was observed that 

 the extracts in all cases were bitter and the residues from the final ex- 

 tractions, although much fainter in taste, were still distinctly bitter. 

 Figure i shows graphically the relative quantity of extract obtained 



in each case. 



(b) Effect of Boiling the Chips 



To determine the effect of boiling on the quantity of extract which 

 may be dissolved from the chips, 10 gm. were boiled under a reflux con- 

 denser in 500 c. c. of distilled water for various periods of time. After 

 cooling and filtering, the filtrate was evaporated and the quantity of 

 extract was determined. Table II gives the results. 



Table II. — Quantity and percentage of extract obtained by boiling 10 gm. of quassia 

 chips in 500 c. c. of distilled water for various periods 



Length of time chips were 

 soaked. 



Hours 



Length of time chips were 

 soaked. 



Hour 



Extract obtained. 



Gm. 



o. 2765 

 .2747 

 •3327 



Per cent. 

 2.76 

 2.74 

 3-32 



