FORMALDEHYDE A8 A POISON FOR HOUSE-FLIES. 



55 



The Deterrence of Formaldehyde. 



The deterrence of formaldehyde was determined by the same method as that 

 employed with formic acid, already described. Each series of different strengths 

 was exposed, one at a time and in quick succession, in the same spot where the 

 numbers of available flies were about constant. The numbers which only tasted 

 and the numbers which drank were counted and the percentage of the latter to the 



100 



90 — 



80 



Xi 70 

 ^ 60 



^50 



•5 



fa 

 o 



10 30 

 ^ 20 



i.o 



— 



— 





_.. 



— 



--, 



— • 



,_. 



1 

 — • • 



— .. 







— - 



;>^ 







^ 



. — . 



r - 



' ~^- 



■^ 



s= 











... .^ 















-— f< 



.J' 











,. 



• 

















^ 



^ 









> 



f 



/ 



=«*=« 



\ 





/ 



/ 











/ 



^ 











/ 



/ 



A> 



/ 



'7 





y 



/^ 













,/ 













,^ 



* 



^ 



/^ 



















y 



/ 



^ 







, ^ 



9 



.<■■ 





/ 



^ 





..• 



m 



■••.. 













/ 







y 



PV^ 































/ 





^ 



■/ 



A 













y 



•••* 





















.' 



V 



V 













./ 

























^ 



/ 





































/ 



/ 













• 



>' 

























r 















^« 





































< 



• 







































• 

 • 



\ 









































■ 











h 



' 







































► 





































































10 9-5, ^-0 8-5 80 7-5 70 65 60 5 5 50 4-5 40 3-5 30 25 20 >-5 10 

 Percentage of striength in di'/ution. 

 r Formaldehyde and water, and control of water. 



50 % lime water „ „ 50 % lime water. 



5 % sugar „ „ 5 % sugar. 



50 % lime water and 5 % sugar. 



Diagram 1. Showing the deterrence of acid formaldehyde and its remedy. 



former gives the factor to the solution. Controls were made with water alone, 

 with 50 per cent, lime water, and 5 per cent, sugar solution, and each series was 

 checked by one or more repetitions. The time allowed to each exposure was five 

 minutes. The following solutions were thus studied : formaldehyde in water ; 

 formaldehyde in 50 per cent, lime water ; formaldehyde in sugar solution ; formal- 

 dehyde in 50 per cent, lime water with sugar. The detailed results are given in 



