THE MONTHLY BULLETIN, 137 



use of heat is unnecessary. The preparation of a very concentrated 

 stock solution is a very simple matter if caustic soda is used. The 

 chief advantages in its use as a solvent are as given above. The chief 

 objection to its use is on account of its causticity. Great care must 

 be exercised in its handling, as its action on the skin is very severe. 

 A spray made up with an excess of caustic soda is more disagreeable to 

 use than one made up with an excess of either soda ash or sal soda. 



A convenient stock solution of sodium arsenite may be made up in 

 accordance with the following formula: 



FORMULAS. 



Granulated caustic soda (9S per cent) 10 pounds 



White arsenic (arsenic trioxide 99 per cent) 20 pounds 



Water, to make 5 sallons 



Mr. R. M. Chapin of the United States Bureau of Animal Industry 

 has proposed that arsenic be dissolved in caustic soda solution by heat 

 of chemical reaction and refers to such a preparation as self-boiled 

 arsenic solution, or S-B cattle dip. Solution may be made as follows : 



Dissolve the caustic soda in two gallons of water in a metal or wooden 

 vessel (preferably iron) and while still hot, add the dry arsenic tri- 

 oxide in a fine stream at a sufficient rate so that the solution is just 

 at the point of boiling, but does not actually boil. Considerable heat 

 is produced by dissolving the caustic soda. Additional heat is fur- 

 nished by the chemical reaction when the caustic soda unites with the 

 arsenic to form sodium arsenite. If the arsenic is added just at the 

 right rate, no extra heating will be necessary'. After the arsenic is all 

 dissolved, let the solution cool and add water to make five gallons. 



Caution! Do not add cold water to the hot solution, as an explosion 

 may result for the reason that the solution is considerably hotter than 

 the boiling point of water. 



If for any reason the arsenic fails to dissolve without the use of 

 heat, the materials have not been wasted, as a solution can then be made 

 by Avarming the mixture slightly, unless the chemicals are of low grade. 

 If hard water is used, there will be some insoluble matter in the solu- 

 tion, but it may be disregarded unless in very large amount. 



This makes a convenient stock solution for diluting to any desired 

 strength ; that is, each gallon contains four pounds of arsenic trioxide ; 

 a quart, one pound; each fluid ounce contains one-half an ounce of 

 arsenic trioxide, 



SUGGESTED DILUTIONS FOR EXPERIMENTS. 



As previously stated, the proper strength of chemical to be used has 

 not yet been determined. For those who wish to conduct independent 

 experiments on this point, the following dilutions may be tried out: 

 Formula 1 diluted to 1 or 1^ gallons. 

 Formula 2 diluted to 20 or 25 gallons. 

 Two fluid ounces of Formula 3 diluted to 1 or 1| gallons. 

 One quart of Formula 3 diluted to 20 or 25 gallons. 

 One gallon of Formula 3 diluted to 80 or 100 gallons. 

 For use on agricultural lands the arsenical should be applied by 

 means of an efficient hand or power sprayer in preference to a sprinkler. 

 Neither the amount of arsenic which can be tolerated by the soil nor 

 3—22640 



