496 DISEASES OF CATTLE. 



the same as the cdinplete exchision of the lierd. 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 48G. In actual practice, however, as some ticks may escape 

 and reinfest the pasture, the time necessary to accomplish eradication 

 may be somewhat prolonged Ijevond 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 Avithout 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 use of arscniccd fZ/'/As/— The formula commonly 

 used in making an arsenical dip is as follows : 



Sodium carbonate (sal soda) poiin(ls__ 24 



Arsenic trioxid (white arsenic) do_— 8 



Pine tar gallon_^ ] 



Water sufficient to malte 500 gallons. 



Put 25 gallons of water into a kettle or tank of -iO 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 vigorously stirring the 

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

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



A l)y-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 have constant watching to 

 ]irevent 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 over 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 undissohed after lioiling. 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 li(|uid after boil- 



1 For fuller information rolative to the prrimration of arsenic clips, see Farmers' 

 Bulletin <;{)::. 



