105 



ELEVENTH REPORT. 



With such an evidence of the uncertainties and Hmitations of a chemical 

 examination of coal tar disinfectants, of which the active constituents are 

 known, what value can there be in such an analysis for insecticides when so 

 little is known of the constituents which give them value or the exact nature 

 of their action? Section (c), Regulation 33, of the specifications quoted 

 requires the presence of ^ of 1% of cresylic acid in the diluted dip, while 

 section (d) requires 2-10 of 1% if, at the same time there is present 8-10 of 

 1% of the hydrocarbons of creosote oil other than Cresylic acid. This 

 implies that 8-10 of 1% of these neutral hydrocarbons is equivalent to 3- 

 10 of 1% of cresylic acid, which is making very fine distinctions when it 

 would be impossible for the point to be proven in practical work. 



Very elaborate methods have been published in Bulletin No. 107, B. A. I., 



