TEXAS FE\TER. 491 



rial, which, however, does not contain any arsenic, may be left after 

 boiling. 



For a stock solution to be kept on hand and used when needed add 

 no tar, but after the solution has become cold make it up to 25 

 gallons, stir well, let settle, and draw off into containers which can 

 be well closed. In this case the tar stock previously described is also 

 required. 



Diluting the dip.— Fivst run water into the vat about three-fourths 

 up to the dipping line, at which its capacity must be known. If tar 

 stock is to be used the necessary amount will be one-third of a gallon 

 for every 100 gallons of vat capacity. Measure it out, mix it with 2 

 or 3 times its volume of water and pour it along the surface of the 

 water in the vat, stirring a little. 



Every 100 gallons of standard-strength bath calls for If pounds 

 white arsenic, which quantity is contained in four-fifths of a gallon 

 of S-B stock or in 5 gallons of boiled stock. From these figures the 

 quantity of arsenic or stock needed to charge the vat may be cal- 

 culated. Or one may base the calculation on the following facts : 



One pound of white arsenic will make 62^ gallons of bath. 



One gallon of S-B stock will make 125 gallons of bath. 



One gallon of boiled arsenic stock will make 20 gallons of bath. 



All solutions of arsenic are considerably heavier than water and 

 if carelessly put into the vat they may plunge to the bottom and 

 be difficult to mix. Therefore always pour the arsenic stock or a 

 proprietary dip in a thin stream evenly along the vat except at 

 the shallow exit end. Another precaution to be taken in handling 

 proprietary dips is never to mix them first with small quantities 

 of water, which may "break" them. Pour them directly into the 

 water in the vat. 



Finally, add water up to the dipping line and stir well. An ex- 

 cellent way to stir is by a pail tied to a rope. Sink it at the en- 

 trance end of the vat and haul it along the bottom to the exit. Then 

 raise it, throw it back to the entrance end, and haul through again, 

 repeating as many times as necessary but always hauling through in 

 the same direction. 



The standard-strength bath prepared as above contains practically 

 0.19 per cent arsenious oxid when fresh. After use oxidation may 

 set in and weaken it, but it will not need to be strengthened so 

 long as it tests not less than 0.175 per cent arsenious oxid. 



To make up small quantities for spraying, to each 5 gallons of 

 water measured out add first 2 fluid ounces (4 tablespoonfuls) of 

 tar stock, and then 5^ fluid ounces of S-B stock or 2^ pints of 

 boiled arsenic stock. 



