June, 1917.] ARSENICAL RESIDUES AFTER SPRAYING. 21 



from two of the plots July 18, before any rain had fallen and from 

 the other two July 21, after a heavy rain of July 20. 



In the case of the blackberries each plot included 2 bushes. 

 The foliage was large and heavy, the fruit abundant and part of 

 the berries were ripe. The bushes were sprayed August 18, 

 using 1^ quarts of spray material to each plot. The spraying 

 was done in the morning. In the afternoon the fruit was picked 

 from two of the plots. The fruit was picked from the other 

 two plots August 24, after a hard rain of August 23. 



Summary of these plots, together with the results of analyses, 

 is given in Table No. 5. Opposite each plot will be found the 

 amount of fruit picked from that plot, the total residue found 

 as expressed in AS2O3, and the residue per quart of fruit. 



It will be noted that with the strawberries the residue AS2O3 

 per quart ranges from 8.6 milligrams to 34.2 milligrams. As 

 was anticipated, these fruits showed a larger residue per unit than 

 would the currants or the blackberries. If we were to assume that 

 1 quart of strawberries will provide a reasonable portion for 4 

 persons, we should have residues per portion ranging from 2 to 8 

 milligrams of AS2O3. 



The residues found on currants ranged from 6.8 milligrams to 

 10.2 milligrams per quart. It seems rather evident that the 

 spray material did not collect in as large amounts on the currants 

 as on the strawberries, quite possibly due to the difference in 

 the surface of the fruit. 



With the blackberries, residues ranged from 3.8 to 11.2 milli- 

 grams per quart. If 1 quart is sufficient to make 4 portions for 

 an adult person, this is the equivalent of .9 to 2.8 milhgrams 

 AS2O3 per portion. 



VEGETABLES. 



Two kinds of vegetables, including 4 plots each, were sprayed 

 with arsenate of lead in the summer of 1916 and the residues of 

 arsenic determined by analysis. The spray material was made 

 up at the rate of 1 oz. of dry arsenate of lead to 2 gallons of water 

 or the equivalent of 3 lbs. of arsenate of lead paste to 50 gallons 

 of water. The vegetables were sprayed directly and thoroly. 



Four plots of cabbages were sprayed, each plot including 3 

 cabbages. The spray was applied August 1. The cabbages from 

 two of the plots were removed August 3 and submitted to analy- 



