131 

 led to additional testing of compounds. The entomological data and selected mass 



spectrometric data will be presented. 



Addition of acid or base to lactic acid 



The experiments in this section were conceived from the knowledge that lactic 

 acid is a known attractant for Ae. aegypti and the hypothesis that differences in 

 human skin pH may affect attraction. Perspiration on the skin is typically near pH 

 5.5 in value. This value may seem slightly acidic due to the popular notion that 

 perspiration should be slightly basic either from the use of basic soaps or from 

 bacterial action which produces an ammonia odor when perspiration is collected and 

 held at room temperature in open air for an extended period of time. 



Five stock solutions of lactic acid in methanol were prepared; spikes of acid 

 or base were added to four of the solutions, leaving the fifth unmodified. The 

 preparation of these solutions was previously discussed in the experimental section. 

 It is important to reiterate that the measured pH values for the solutions serve only 

 as a reference scale. The unmodified solution yielded a pH 3.1 reading. 



The percentage of Ae. aegypti attracted to each of the five solutions is 

 presented in figure 3-13. The acidified solution is shown to have slightly less 

 attraction than the unmodified solution; however, the trend for solutions with 

 increasing base added is more apparent; the successive addition of base decreases 

 the attraction. 



The reactions from the previous section as well as a chemical explanation for 

 the results depicted in figure 3-13 are illustrated in figure 3-14. Experiments 



