ASSAY OF ARSENICAL DIPPING FLUIDS. 6 



nate is probably somewhat less than half as powerful as arsenic in 

 the form of arsenite in its effects upon both cattle and ticks. Also 

 it has recently been observed that arsenical baths under certain con- 

 ditions sometimes display the converse phenomenon of reduction — 

 that is, arsenate tends to be reconverted to arsenite. Laws, in the 

 article above mentioned, suggests that the phenomenon of reduction 

 may likewise be attributable to the action of microorganisms, of 

 course of different species from the organisms which cause oxidation. 

 Recent work in this laboratory has substantiated the correctness of 

 Laws's surmise. Pending the completion of certain researches it may 

 simply be stated here that both phenomena have been observed to 

 occur in baths in actual use in the field, sometimes in the same bath; 

 that is, a single bath may show alternating tendencies in the two 

 directions, first toward oxidation, then toward reduction followed by 

 oxidation again, and so on. The primary condition which determines 

 in which direction the change shall progress at any given time or in 

 any particular bath is the degree of use which the bath is receiving. 

 Under present ordinary conditions which appear to prevail in the 

 field a gradual oxidation may be looked for. It is only in vats 

 through which cattle are passed in exceptionally large numbers and 

 at very frequent intervals, such as the vats at some of the stockyards 

 centers, that reduction as a separate phenomenon becomes apparent. 



A consideration of the above facts renders sufficiently obvious the 

 necessity for some analytical control of the baths used for dipping. 



The assay of arsenical dipping fluids, at least with sufficient 

 accuracy for practical purposes, is not a difficult matter. It is no- 

 where described in chemical literature, however, and the average 

 chemist, when offered the problem, will be somewhat daunted, not 

 knowing how he may best set to work to obtain good results without 

 a considerable expenditure of labor. It is believed that some of the 

 methods herein to be described can be successfully executed by per- 

 sons who possess but a limited chemical training. In almost every 

 section of the country there should be some one, pharmacist, physician, 

 veterinarian, instructor in school or college, or even student, who 

 would find it worth while for a comparatively small fee (provided a 

 sufficient number of samples are sent in from various sources) to 

 undertake the assay of such preparations. A 4-ounce sample * is 

 sufficient, though a larger quantity is rather more convenient for the 

 analyst. 



It is also purposed to describe a portable testing outfit that has 

 been devised for the use of bureau inspectors in the field, and that 

 enables them, without the possession of any chemical knowledge 

 whatever, at the side of the vat and in a few minutes, to determine 



1 For precautions necessary in sending samples see page 4. 



