30 Farmers' Bulletin 1057. 



less injurious to cattle than sodium arsenite. Field experience, too, 

 indicates that under ordinary conditions, provided the vat has been 

 cleaned out and freshly charged in the spring, danger of injury from 

 this cause need not be considered. 



In practice, baths nearly always are both strengthened and re- 

 plenished in one operation and it is decidedly the simplest and best 

 procedure. First run water in up to the dipping line, at which 

 the capacity is known, and stir thoroughly. Take out a sample and 

 test it to determine the per cent of arsenious oxid. Then find out, by 

 referring to Table 4, how much arsenic or stock, whichever is to be 

 used, is actually contained in 100 gallons of the bath as it stands. 

 Subtract that (juantity from the quantity wIill-Ii corresponds 

 to the desired strength of bath, and multiply the remainder by the" 

 number of hundreds of gallons of vat capacity. This calculated 

 quantity of stock, by strict mathematics, is not quite sufficient to 

 reach the desired percentage, particularh" if the comparativeh^ 

 weak boiled stock is used, but it will be close enough for all practical 

 l)urposes. 



Another method of calculation which requires no reference table 

 and is particularly useful when proprietary^ dips are employed, is the 

 following: If it is not already known, calculate the quantity of 

 arsenic or concentrate which would be needed to make up an entirely 

 fresh charge of the desired strength. Then determine the fractional 

 part of this quantity necessary to raise the strength of the existing 

 bath to the desired point. For example, suppose 10 galhms of a certain 

 proprietary dip is required for a fresh charge of the vat to the de- 

 sired strength of 0.18 per cent arsenious oxid, while the strength 

 of the vat actually in the vat is found hj test to be 0.15 per cent. 

 Then the bath is too weak by 0.03 per cent, aral three-eighteenths of 

 10 gallons of the dip will have to be added. 



In course of time filth and mud will accumulate in the bath to 

 such an extent that the vat will need to be emptied, cleaned out and 

 recharged. Cattle dipped in a bath loaded with filth and mud will 

 necessarily carry out more bath on their bodies, and so more arsenic 

 than they should; also they will dry off more slowly, and very 

 naturally will be more likely to be blistered. By the same line of 

 reasoning some field men of the Bureau of Animal Industry say that 

 after a vat has been charged no more tar or tar stock should 

 be added in replenishing the bath, particularly if work oxen are to 

 be dipped. From experience they have come to believe that tar 

 cements together the fillh and mud carried out by the animals and 

 so increases the chance of injury. At any rate it ai)pears to be good 

 practice to reduce the quantity of tar added as the bath becomes 

 dirtier. 





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