SHEEP TICK AND ITS ERADICATION BY DIPPING. 19 



lime-sulphur-arsenic dip. This dip probably will eradicate sheep 

 ticks with one dipping- when all conditions are favorable, but one 

 dipping can not be depended upon in practical operations. It will 

 undoubtedly eradicate ticks if the flock is given two dippings, and it 

 has the advantage that it may be used in almost any of the hard 

 waters without injury to the animals from that cause. Its disad- 

 vantages are that there is no test by which the rate of deterioration 

 may be determined in the field and that it is more difficult to prepare 

 than some of the other dips. None of the dips tried in the bureau's 

 investigations can be depended upon to eradicate sheep ticks wnth 

 one dipping. 



COAL-TAR-CREOSOTK DIPS. 



The coal-tar-creosote dips are sold under a large number of trade 

 names. They are made from coal-tar derivatives and the principal in- 

 gredient is so-called creosote oil, which is made soluble in or miscible 

 with Avater by means of soap. When diluted with suitable water they 

 are very efficacious in eradicating sheep ticks from a flock if two dip- 

 pings are given with an interval of 24 to 28" days betw^een dippings. 

 There is no field test for determining the deterioration of these dips, 

 and consequently in replenishing the dip the percentage of active 

 principle in the vat is largely a matter of guesswork. 



These dips should contain, when diluted ready for use, not less 

 than 1 per cent by weight of coal-tar oils and cresylic acid. In no 

 case should the diluted dip contain more than four-tenths of 1 per 

 cent nor less than one-tenth of 1 per cent of cresylic acid ; but when 

 the proportion of cresylic acid falls below two-tenths of 1 per cent 

 the coal-tar oils should l)e increased sufficiently to bring the total 

 of the tar oils and the cresylic acid in the diluted dip up to 1.2 per 

 cent by weight. 



In the undiluted coal-tar-creosote dips, especially in cold weather, 

 a separation of naphthalene and other constituents of the dip may 

 occur. Care should therefore be taken to see that the dip is homo- 

 geneous in character before using any portion of it. 



CRESOL DIPS. 



The cresol dips are sold under various trade names, and consist 

 of a mixture of cresylic acid with soap. The term cresylic acid as 

 used in this connection covers those cresols and other phenols de- 

 rived from coal tar, none of which boil below 185° C. (365° F.) nor 

 above 250° C. (482° F.). When diluted ready for use a cresol dip 

 should contain one-half of 1 per cent of cresylic acid. As there 

 is no field test available for cresol dips, the rate of deterioration 

 can not be determined at the vat, and consequently after a ieyf 

 sheep have been dipped there is no method known for keeping con- 

 stant the percentage of cresylic acid in the used dip. 



