160 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 



idea being tliat the excess of the oil ou the surface of the leaves would 

 be taken up by the ashes, and thus prevented from entering into the 

 system of the plant, while at the same time the ashes would not inter- 

 fere with the effect of the oil upon the worms. 



The following account of Dr. Keal's experiments with improved kero- 

 sene emulsions is from his report, published in Bulletin 1 of the En- 

 tomological Division : 



As flirected, I liave confined ray experiments to emulsions of kerosene, and noted 

 tlie effects of applications of sucli solutions upon the cottou-plants and Cotton Worms. 



My efforts were made to determine: 1. Substances best adapted to emulsify kero- 

 sene; 2. Maximum dilution of kerosene destructive to the larvae; 3. Minimum dilu- 

 tion of kerosene destructive to the cotton-plants. 



It was soon apparent that kerosene could not be used to advantage simply with 

 water, from its tendency to collect at the top ; nor if the water were made slightly 

 alkaline or acid would much benefit be observed. 



A strong solution of various soaps made a good emulsion, presenting some points of 

 advantage. 



Soda soap, potash soap, whale-oil soap, and other varieties were tried, but a cheap 

 grade of yellow bar-soap, especially one in which rosin was largely used, proved best, 

 and suggested the manufacture of a soap containing a still larger quantity of rosin, 

 which could be cheaply sold for this purpose. 



After many trials I found that 4 jiounds of this soap to 1 gallon of hot water would 

 emulsify 1 gallon kerosene, forming a gelatinous compound that was quite stable. 



Less than this percentage of soap acted badly with kerosene, and a greater amount 

 did not appear to emulsify a large amount of kerosene. 



This mixture, containing 50 per cent, kerosene and costing 26 cents per gallon, I 

 adopted as a standard. 



I prepared the following dilutions: 



A. One gallon standard solution to 24 gallons water, 2 per cent, kerosene, cost 1.04 

 cents per gallon. 



B. One gallon standard solution to 39 gallons water, 1.25 per cent, kerosene, cost 

 0.65 cents per gallon. 



C. One gallon standard solution to 49 gallons water, 1 per cent, kerosene, cost 0.52 

 cents per gallon. 



D. One gallon standard solution to 79 gallons water, 0.625 per cent, kerosene, cost 

 0.325 cents per gallon. 



E. One gallon standard solution to 99 gallons water, 0.5 percent kerosene, cost 0.26 

 cents per gallon. 



Emulsions A. B, and C presented a milky color, and were quite permanent; D and 

 E showed some tendency to disintegrate after four days' standing. 



I tried solutions of many native plants, and found the zamia finely adapted for an 

 emulsion, especially when used immediately. 



Six pounds of zamia ''roots" were washed and grated. The pulp boiled an hour 

 in 3 gallons of water ; then strained, and while hot stirred in 4 ounces sal-soda. This 

 emulsified 1 gallon kerosene, forming a beautiful pinkish jelly, containing 25 percent, 

 kerosene, costing 6 cents per gallon. One gallon of this solution was added to 24 gal- 

 lons of water. This emulsion contained 1 per cent, kerosene, and cost 0.24 cents per 

 gallon. 



Dextrine, starch, flour, mucilage of bene (sesamum) leaf, mucilage of root of Pteris 

 aquiluia, and othr^r substances were tried, but proved to be of little value. 



Milk emulsions. — By gradually adding, with agitation, one gallon kerosene to one 

 gallon fresh milk, an elegant emulsion was formed that bore dilution well, but as 

 fresh milk is often not attainable the condensed milk was used, and the following 

 seemed most easily made : 



One part condensed milk dilute with five parts water j to this add gradually ei^ht 



