The Bulletin. 19 



The soap is shaved into a kettle containing the water, which is 

 boiled until the soap dissolves, then remove from the fire and add the 

 kerosene. The mixture is then pumped through the spray pump and 

 nozzle back into itself until it has the appearance of thick milk and 

 no globules of free kerosene can be noticed. This stock solution 

 will keep indefinitely. For use, take 1 gallon of stock and add 6 

 gallons water. 



DANGER FROM THE USE OF ARSENATES ON TOBACCO. 



There exists in the minds of many people a strong prejudice 

 against the use of poisons (arsenates) on any plant that is used for 

 a food. Needless to say this same prejudice has to be met when one 

 advises the use of arsenates for tobacco spraying. Of course, caution 

 should be used in this matter. We would not apply any poison to to- 

 bacco directly before it is harvested, and some time should always 

 intervene from the time of the last spraying until the tobacco is 

 harvested. Certainly two weeks should be allowed, and three or four 

 would be much better. Then by the time the tobacco is harvested the 

 wind and rains have had a chance to remove all but the last traces of 

 poison. To show clearly that the amount of arsenate used on tobacco 

 is not at all dangerous, it is necessary only to call attention to the 

 following facts: (1) At the rate arsenates are used, not enough 

 could be secured by any one person at any one time to prove injurious. 

 (2) Not all of the spray mixture used reaches the plant. (3) Of 

 the amount that does reach the plant only a very small percentage 

 can remain until the end of the season. 



The amount of arsenate used originally is not sufficient to cause 

 alarm. Our experiments show that 4 pounds of arsenate of lead 

 would spray an acre of tobacco. The average sample of arsenate of 

 lead contains from 10 to 20 per cent of arsenous oxide (arsenic), 

 which is the real poison in the arsenate of lead. One and one-half 

 grains of arsenic are said to constitute a fatal dose for an adult. In 

 4 pounds of arsenate of lead there would be from 2,800 to 5,600 

 grains of arsenic, depending upon the strength of the arsenate of 

 lead used. Assuming, then, that all of the arsenate used reaches the 

 plant, and that all of it remained upon the leaf until harvest time, 

 there would be left on each acre of tobacco for every spraying made, 

 from 1,860 to 3,730 injurious doses. Assuming that three sprayings 

 are made during the season, there would be at the end of the year 

 8,400 to 16,800 grains of arsenic on an acre of tobacco, provided all 

 of the spray mixtures used reached the plant and that none of it was 

 washed off or blown away during the season. In other words, there 

 would be approximately 3 grains for each plant. However, as stated 

 below, at least 25 per cent of the original mixture used is wasted, and 

 certainly it seems safe to say that 95 per cent of the amount that 



