MICHIGAN ACADEMY OF SCIENCE. 107 



by whuh the various ingredients of such dips may be determined with ex- 

 actness, no detail having, apparently, escaped the analyst. 8uch exactness 

 is, of course, commendable where any good can result, but when there appears 

 not to have been any test made to determine whether a difference of 10% 

 in the quantity of the supposedly active ingredients can be detected in the 

 efficiency of the dip and when, as an actual fact, such a difference is almost 

 , impossible of detection, the absurdity of such extreme exactness is apparent 



Cresol Dip: ' 



Linseed Oil Soap U. S. P. 



Cresyhc Acid B. P. 185° to 210°. 

 Cresote Oil Dip: 



Cresote Oil 77 with 20% Cresyhc Acid. 



Rosin 17 



Caustic Soda 1 



Water 4 



Sulphur 1 



ANALYSIS OF CREOSOTE OIL DIPS INCLUDES DETERMINATION OF: 



Water. 



Soda and Pyridine Bases. 



Phenols. - : 



Neutral rosin substances. 



Light oils. 



Naphthalene and solid hydrocarbons. 



Creosote oil. 



(Bull. 107 Bureau of Animal Industry). 



Another reason why such elaborate methods are of little value is that the 

 standardization of a dip is made on the basis of two ingredients only, namely, 

 the hydrocarbons and the phenols or tar acids, the dilutions allowed being- 

 based on these factors alone, the other ingredients — resin, alkali and water — • 

 being of value only to bring about proper physical conditions, while a physical 

 test is made to determine whether the proper quality of emulsion can be 

 made. 



Recognizing the necessity for some means of standardizing insecticides 

 and, especially, those composed of material like creosote oil, a method was 

 evolvetl which, although inaccurate when compared with chemical exactness, 

 is actually a means of maintaining a certain degree of uniformity in such 

 products; but, what was of far greater value, it lead to the discovery that it 

 is possible to prepare a creosote oil dip having an efficiency many times 

 greater than that of the average of such preparations. This was brought 

 about by a judicious mixture of biological and chemical methods, to which 

 the name "Biochemic" might be applied, to borrow the word used by the 

 Bureau of Animal Industry. This method was first published in a paper 

 which appeared in the 10th Report of the Michigan Academy of Science, 

 and to this we can refer you for additional data. In brief, it is as follows: 



Some insect of which a more or less constant supply is available should 

 be selected as the test organism. The apparatus needed is of the simplest 

 kind, consisting only of a cylinder with graduations of 1 cc. to 100 cc. for 

 making dilutions, some 2-inch glass tidies, open at both ends with a 

 diameter of al)out one-half inch, in which to place the insects, with porous 



