MICHIGAN ACADEMY OF SCIENCE. 10.5 



The constituents may be of such a complex character that the presence 

 or absence of one of them might pass unnoticed or be disregarded in a chemical 

 assay. 



When any substance is standardized by pharmacological assay, no definite 

 percentage of active constituents is claimed, but only that its activity has 

 been determined l)y actual test on animal, insect or germ to be fully ec^ual 

 to standard, and, therefore, that under ordinary conditions a certain amount 

 or a certain dilution will be found efficient. 



Standardization by chemical test, however, can be more specific, and the 

 specifications to the manufacturers of creosote oil dips is given in definite 

 quantities of oil and cresylic acid, which must appear in an approved dilution. 



The following specifications have been promulgated by the Bureau of 

 Animal Industry, of the U. 8. Department of Agriculture: 



"And pending further investigation the following dips may be used for 

 the eradication of sheep scab: 



(a) Cresol dip, which consists of a mixture of cresylic acid with soap. 

 When diluted ready for use, this dip should contain ^ of 1% of cresylic acid. 



(1)) Coal-tar creosote dip. This dip when diluted for use should contain 

 not less than 1% by weight of coal-tar oils and cresylic acid, nor less than 

 1-10 of 1% of cresylic acid; but when the proportion of cresylic acid falls 

 below 2-10 of 1%, the coal-tar oils should be increased sufficiently to bring 

 the total of the tar oils and cresvlic acid in the dilution up to 1.2% by weight. 

 Reg. 33. B. A. I. Order No. 143. 



Saturating the interior surfaces of cars, etc. with 5% solution of carljolic 

 acid or a solution containing 2% of cresol, — where this is used it must be 

 mixed with soft soap to make it more easily soluble in water." Reg. 45. 

 B. A. I. Order No. 143. 



The extracts quoted are the specifications the Bureau of Animal Industry 

 considers sufficient to secure the best coal-tar insecticide for the treatment 

 of sheep scab. With no knowledge of how such a preparation affects the 

 insect, whether as a poison or mechanically, and with, evidently, no know- 

 ledge of what constituents of the oil — the acid, neutral or basic — are of 

 yalue, a chemical basis of standardization is adopted and measures taken 

 to enforce these requirements in special cases. There is, apparently, the 

 idea that germicidal and insecticidal values are dependent upon the same 

 constituents, since tar acids or cresylic acid are required in solutions for 

 both purposes. The fact that the relative values of gemicidal preparations 

 may be roughly determined by chemical test is frankly admitted to be the 

 reason for adopting a similar method of assay for in.secticides. There is a 

 radical difference, however, between the two cases, as the value of coal tar 

 disinfectants is known to reside almost entirely in the tar acids, the cjuantity 

 and characteristics of which may be easily determined by chemical assay. 



But, even for the standardization of coal tar germicides, a chemical assay 

 is of only limited value, as the tar acids from some oils seem to have a selec- 

 tive action on certain bacteria, destroying them in high dilutions, while 

 others of different origin, but having almost the same physical and chemical 

 properties, recjuire much stronger solutions to produce the same results. 

 Two samples of cresylic acid, 98% pure, having boiling points ranging from 

 200° to 250° C. with practically the same amount distilling between any two 

 degrees, have been found to have the values 1, 4 and 16, using carVjolic acid 

 as the unit and B. Typhosus as the test organism, while with B. Pyocyaneus 

 as the test organism the relative values are 1, 2 and 4, which is graphically 

 shown in the accompanying chart. 

 14 



