to wind and wave action. In general, sodium arsenite treatment is 

 not practical where the average depth exceeds 8 feet, and where the 

 length of shoreline to be treated is less than about 200 feet 

 (Mackenthun, 1958). 



In the spraying of lakeshore properties, efforts are usually 

 made to get property owners to join in combined efforts to rid 

 their shorelines of weeds by treating adjoining beaches simultane- 

 ously. 



In large scale operations, the heavy drums of sodium arsenite 

 are placed on a barge or upon a platform placed upon two boats 

 secured side by side and propelled by outboard motors . Domogalla 

 (1926, 1935, 1959), a pioneer in the field of large scale weed 

 control treatments, has used a trailer for lake work (see Figure 3). 



Thorough mixing of chemical and water in a large operation 

 may be brought about by pumping water directly from the lake by 

 means of a self-priming centrifugal or gear pump, which also draws 

 a regulated volume of sodium arsenite from a drum of the concentrated 

 chemical at the same time. Water from the lake is drawn through a 

 suction hose hung over the side of the barge or platform. On the 

 intake side of the pump, the hose is connected to a 45° Y-branch to 

 which a second hose, connected with a sodium arsenite drum, is also 

 attached. Valves are located in each intake hose line ahead of 

 the Y-branch for controlling rate of dilution of the chemical. 

 The mixed chemical is delivered under pressure from the discharge 

 side of the pump to distances of 40 to 50 feet from a fire hose 

 nozzle held in the hands of the operator. 



Figure 9 illustrates the equipment used in Wisconsin 

 (Mackenthun, 1958) and elsewhere in spraying extensive areas with 

 sodium arsenite where a pump with 1% inch suction and one inch 

 discharge is used. 



For a pump with a 1% inch suction and one inch discharge, 

 the following fittings are used on the suction end : strainer and 

 foot valve; about 7 feet of 1% inch (I. D.) suction hose; 1% inch 

 gate valve on intake line; nipple connection to a 1% inch 45° 

 Y-branch, nipple connection to a second 1% inch 45° Y-branch where 

 a connection is desired to a second sodium arsenite drum so spray- 

 ing will not be interrupted in switching to a new drum of chemical; 

 nipple, and union connection to suction end of pump. On the dis - 

 charge end of pump: a 1 3/4 inch reducer; nipple, union, and nipple; 

 a sufficient length of 3/4 inch pressure hose attached to a smooth 

 fire hose nozzle with 3/8 inch opening to allow freedom of movement 

 in directing the spray from the deck of the barge or platform. 



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