496 DISEASES OF CATTLE. 



the same as the complete exchision of the herd. The dates on which 

 the starving out of an infestation will be effected when begun at 

 various times of the year have already been given in the table on 

 page 486. In actual practice, however, as some ticks may escape 

 and reinfest the pasture, the time necessary to accomplish eradication 

 may be somewhat prolonged beyond the periods indicated in the 

 table. This method offers the advantage that the pasture may be 

 used continuously, and is the one usually followed. 



Many efforts have been made to discover a practical method for 

 dipping cattle to destroy ticks without injury to the cattle, and the 

 bureau has experimented for years with this object in view. Numer- 

 ous kinds of dips have been used, and many failures have been 

 recorded, but finally a very satisfactory dip has been discovered in 

 an arsenical solution, and arsenical dips, in fact, are now the only 

 kind used in tick eradication. 



Preparation and vse of arsenical dips} — The formula commonly 

 used in making an arsenical dip is as follows : 



Sodium carbonate (sal soda) pounds__ 24 



Arsenic trioxid (wliite arsenic) do — 8 



Pine tar sallon__ 1 



Water sufficient to make 500 gallons. 



Put 25 gallons of water into a kettle or tank of 40 to 50 gallons 

 capacity, heat to boiling, and add the sal soda. When this has dis- 

 solved add the white arsenic, then boil and stir for 15 minutes or 

 longer, until the white arsenic has entirely disappeared. Cool to 

 140° F. (by the addition of cold water if desired), then pour in the 

 pine tar in a thin stream while constantly and vigorousl}' stirring the 

 .solution. Immediately empty the liquid into the dipping vat, which 

 has already been three-fourths filled with water, and stir thoroughly. 



A by-product of the action of sodium carbonate on white arsenic 

 is the gas carbon dioxid. The escape of this gas is attended with con- 

 siderable foaming of the solution, so the kettle must be generously 

 large, and the operation of boiling must liaA'e constant watching to 

 prevent the liquid from frothing over the edge of the kettle. 



The kettle or tank, utensils, and materials must be perfectly free 

 from all greasy or oily substances, as a small quantity of such matter 

 is sufficient to form a coating OA^er the arsenic, and thus to prevent 

 or delay its solution. 



The boiled dip may be made perfectly well with very hard water, 

 but in that case some residue of a fine white or gray powder will be 

 left undissolved after boiling. This residue carries no arsenic, but 

 arises from the action of the sodium carbonate upon compounds, 

 chiefly of lime, in the water. Examination of the liquid after boil- 



1 Tor fuller information relative to tlio proparation of arsonie dips, soo Farmers' 

 Bulletin 603. 



