New York Agricultural Experiment Station. 379 



compressed-air outfits. 



Spraying outfits which use compressed air are of relatively recent 

 introduction and have not been widely or thoroughly tested. They 

 have the advantage of giving an evener pressure and the power 

 forms are very much lighter than are other power outfits. But with 

 some of them pressure cannot be maintained so high as with steam 

 engines or gasoline engines. However, if a pressure of 50 pounds 

 or more can be constantly maintained, such an outfit as this is in 

 many respects superior to a hand pump outfit. 



Further experiments are necessary to demonstrate the value of 

 these outfits for use on high trees as compared with steam or gasoline 

 outfits. 



Compressed air outfits do not have mechanical agitators and do 

 not appear to be well adapted for use with spraying mixtures con- 

 taining heavy particles, such as paris green, unless some device is 

 adopted for agitating the liquid by means of a jet of compressed 

 air through the liquid from beneath, as is sometimes employed. 



Compressed air sprayers are of two types, first, those in which only 

 one chamber is used for both air and liquids, and second, those in 

 which a separate chamber is used for each. Most of these outfits 

 are of the former type and in these the tank is filled only about two- 

 thirds full of liquid, the rest of the space being left for compressed 

 air. But in outfits of the second type, represented by the Pierce- 

 Loop outfits, the tank for the liquid is filled full. 



In knapsack forms the tank is circular. It may be suspended from 

 the shoulders or may be carried in the hand. One form is made 

 by D. B. Smith & Co. It has an air pump attached to the tank. The 

 same firm makes a knapsack sprayer, the power for which is fur- 

 nished by squeezing a bulb just behind the nozzle. 



The Rippley Hardware Co. makes a wheelbarrow outfit and knap- 

 sack outfit on the same principle. In both of these agitation of the 

 liquid is provided for by the pumping in of the air at the bottom 



