To prepare the stock emulsion for use, it is diluted with water to a 20 or 25 per cent emulsion. In order to obtain a 20 per cent emulsion of oil, it is necessary to use one part of the stock emulsion to three parts of water, and for a 25 per cent emulsion, one part of stock emulsion to 2$ parts of water. The stock emulsion is permanent, but the diluted emulsion does not remain uniformly mixed, so that if allowed to stand it should be thoroughly mixed by stirring before using. Only rain or freestone water should be used for diluting, and if this is not available, the water should be " softened " by adding a sufficient amount of concentrated lye, sal soda, or washing powder. Care should be observed in this process not to use an excess of these preparations.
An 80 per cent stock emulsion is on the market, and much time and labor can be saved by obtaining this instead of making the emulsion. To prepare it for use, it should be diluted in the same manner as indicated above for the home-made stock emulsion.
The arsenical dip. — This dip is used considerably, on account of its cheapness and the ease with which it is prepared. In general, it has proved very effective in destroying ticks, and is less likely than crude petroleum or emulsions of the same to injure cattle when dipping has to be done in hot weather. Some injury to the skin is, however, likely to occur when the arsenical mixture is used, and this injury, which will be so slight as to be scarcely noticeable if the cattle are properly handled, is liable to be serious if the cattle are driven any distance, especially if allowed to run while being driven within a week after treatment. The formula given below for making an arsenical dip is the one most commonly used in this country : —
Sodium carbonate (sal soda) .............. 24 lb.
Arsenic trioxid (white arsenic)..............8 lb.
Pine tar.....................1 gal.
Sufficient water to make 500 gallons.
If a stronger arsenical dip is desired, ten pounds of arsenic may be used in place of eight pounds, but in general the stronger solution should not be used. In warm weather particularly it is not advisable to use a solution stronger than that given in the above formula, if the animals are to be treated every two weeks.
In preparing the dip, a large caldron or galvanized tank is required for heating the water in which to dissolve the chemicals. Thirty or forty gallons of water should be placed in the caldron or tank and brought to a boil. The sodium carbonate is then added and dissolved by stirring. When this is accomplished, the arsenic is added and dissolved in a similar manner. The fire is then drawn and the pine tar added slowly in a thin stream and thoroughly mixed with the dip by constant stirring. This strong stock solution is diluted to 500 gallons before using.
The diluted arsenical solution may be left in the vat and used repeatedly, replenishing with the proper quantities of water and stock solution when necessary. When not in use, the vat should be tightly covered with a waterproof cover to prevent evaporation on the one hand and further dilution by rain on the other hand. Securely covering the vat when not in use also lessens the risk of accidental poisoning of stock and human beings.
On account of the fact that arsenic is a dangerous poison, great care must be observed in making and using the arsenical dip. From the time the arsenic is procured from the druggist until the last particle of unused residue is properly disposed of, the most scrupulous care should be taken in handling this poison. Guessing at weights or measures or carelessness in any particular is liable to result in great damage, and not only may valuable live-stock be destroyed, but human beings may lose their lives as well.
In the use of arsenical dips care should be taken not only to avoid swallowing any of the dip, but persons using the dip should also bear in mind the possibility of absorbing arsenic through cuts, scratches, or abrasions of the skin, and the possibility of absorbing arsenic by inhalation of vapors from the boiler in which the dip is prepared or by the inhalation of the finely divided spray when the spray pump is used. It should be remembered that the absorption of even very small quantities of arsenic, if repeated from day to day, is liable ultimately to result in arsenical poisoning.