AKSENICAL CATTLE DIPS. 9 



of chemical analysis, have heeu elsewhere discussed by the writer,' Here it is 

 sufficient to note that even if all precautions are talien against leakage, either 

 in or out, against evaporation, and against mistakes in measurements, etc., 

 still the bath is likely to change its strength owing to the action of micro- 

 organisms which grow therein in si^ite of the presence of the poisonous arsenic. 

 As already mentioned, the active ingredient of the bath is an arsenite, either 

 of sodium or potassium. One species of microorganism is able •to take oxygen 

 from the air and to combine it with the arsenite, thus forming an arsenate, a 

 distinctly different compound of arsenic, and one which is much les^ poisonous 

 to ticks. This species of microorganism appears to flourish in nearly all dip- 

 ping baths under ordinary conditions of use and operates to gradually weaken 

 the bath. There is, however, another si^ecies of microorganism which occa- 

 sionally makes itself manifest in baths through which cattle are passed in ex- 

 ceptionally large numbers or at frequent intervals, and which operates in pre- 

 cisely the opposite manner, namely, to reduce any arsenate which may be 

 present to arsenite, thus rendering the bath stronger. 



The chemical analysis of arsenical baths with sufBcient accuracy for practi- 

 cal purposes is not a difficult matter. It does, however, require some chemical 

 training and equipment If State officials concerned with dipping can not 

 make provision for the execution of analyses, it should not be difficult to find 

 Bomeone — physician, veterinarian, pharmacist, instructor in school or college, 

 or even a student — who, for a fee. which might be comparatively small if a 

 sufficient number of samples' from various sources could be counted, on, would 

 find it worth while to undertake this work. It Is desirable to have the 

 " actual arsenious oxid " — that is, the amount of arsenic existing as arsenite — 

 determined at least once a month, and the " total arsenious oxid " — that is, 

 the amount of arsenic existing as both arsenite and arsenate — determined at 

 least every two months. To avoid danger of poisoning cattle, it is safer to 

 discard the bath entirely whenever the " total arsenious oxid " would rise 

 above 0.25 per cent for the low-strength bath or above 0.30 per cent for the 

 high-strength bath after the bath had been adjusted to contain the proper 

 amount of " actual arsenious oxid." 



In taking samples for analysis certain precautions are necessary. First, 

 the bath must be well stirred; next, the sample is filled at the vat side into 

 the bottle in which it is to be sent to the analyst. The bottle should hold not 

 less than 4 fluid ounces (one-fourth, pint) and should be filled up to the neck. 

 Unless the sample can be placed in the hands of the analyst in a very few 

 hours it should be treated with formaldehyde to preserve it from the action of 

 microorganisms which may affect the arsenic and which may work very rapidly 

 in the sample after its removal from a comparatively cool location under- 

 ground and exposure to hot summer weather. A little concentrated formalde- 

 hyde solution (37 per cent) may be cheaply obtained from the druggist, to- 

 gether with a medicine dropper. The formaldehyde is to be carefully added 

 to the sample with the medicine dropper, in the proportion of exactly .5 drops 

 to each 4 ounces of sample (20 drops to a pint). The bottle is then to be 

 immediately corked, the cork and lip of bottle wiped dry and completely 

 covered with melted sealing wax, rosin, or some similar material, in order to 

 exclude air. A few matches will furnish the heat necessary for melting the 

 sealing material. The analyst should be informed of exactly what steps were 

 taken in preparing the samples, and the latter should be shipped to him without 

 delay. 



' 1 Department of Agriculture Bulletin 76. 



