514 Journal of Agricultural Research voi. x, No. 10 



claims that quassiin is slightly soluble in water, and is readily soluble 

 in the caustic alkalies, but is not soluble in the alkali carbonates. Table 

 VII further shows that extracts from chips boiled for 5 hours are slightly 

 more effective than those from chips soaked for 24 hours, results agree- 

 ing with those of the quantitative determinations. But the effectiveness 

 of the first extract from chips soaked for 2 hours is only slightly better 

 than that of the second extract, whereas the ratio should be 4 to i, in 

 order to agree with the quantitative determinations; however, experi- 

 ments performed in the laboratory on a large scale (p. 515) with the first 

 and second extracts give a ratio of about 5 to 2. The most important 

 result recorded in Table VII is that the soap-solution extract and lye- 

 solution extract are equally effective, but, when the solutions containing 

 the extracts are diluted, the former with soap solution and the latter with 

 water, it is readily seen that the dilutions containing the soap-solution 

 extract are much more effective and more economical, because they 

 already contain the necessary "spreader," while the lye dilutions to be 

 equally effective must have soap added to them before they are applied. 



3. — EFFECTIVENESS OF SOME ECONOMIC FORMULAS 



The preceding preliminary experiments clearly show that extracts 

 from quassia chips soaked in water are less effective than those from 

 chips boiled in water; but, on the other hand, extracts from chips 

 soaked in soap solution, sodium-carbonate solution, and lye solution are 

 more effective than those from chips boiled in these three solvents. 

 This seems to indicate that at a high temperature alkalies decompose 

 quassiin. As already stated, soap-solution and lye-solution extracts, 

 not boiled, are the most effective ones found; and of these two extracts 

 the former is the more economical and perhaps the more efficient for 

 practical work. The soap-solution extract was further tested in the 

 laboratory before it was applied in practical work, but the lye-solution 

 extract did not seem to warrant further tests. 



The following experiments were therefore performed with variously 

 concocted formulas containing soap-solution extract to determine whether 

 or not quassia extract may be employed as a general insecticide for all 

 aphids. In each formula the soap was used in the proportion of 1.6 

 pounds to 100 gallons of water. This amount of soap has no detrimental 

 effect upon the plants sprayed and very little upon the aphids. 



To be able to compare more accurately the effectiveness of the various 

 formulas, experiments were first performed in the laboratory on a small 

 scale, and then outside the laboratory on a larger scale; with this method 

 the live insects in the laboratory were counted at regular intervals, but 

 outside the laboratory they were generally estimated. In order to have 

 a standard by which the efficiency of quassia extract might be judged, 

 nicotine sulphate in soap solution and also in water was sprayed upon 

 aphids. 



