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JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 15 



to soften the water with chemicals. In recent years insecticides com- 

 patible with hard water are coming into more general use which, with 

 the growing use of dusts, may be the solution of the problem. 



Water Softening 



The removal of temporary hardness from water by^ boiling is too 

 expensive to be applied in spray practice, hence we must depend on 

 chemical water softeners. The function of such chemicals in making 

 oil emulsions is: — (1) to react with the salts in the water and thus re- 

 duce the soap consuming power; (2) to aid in emulsifying the oil; 

 and (3) to prevent the formation of insoluble calcium and magne- 

 sium soaps, these having a tendency to clog the spray nozzle. 



The chemicals commonly used for this purpose are caustic soda 

 (NaOH), Soda Ash (a crude product), Sal Soda (Na2CO3-10 H2O), 

 Lye (a mixture of caustic and carbonate of soda), commercial water 

 softeners (caustics, carbonates and phosphates), and ammonia. 



Caustic soda was found to be superior, in the locality where the 

 survey was made, to any other form tested. This was especially 

 true in very hard waters. The value of caustic soda in softening 

 hard water is shown in Table II. 



Table II. — The Value of Caustic Soda as a Water Softener 

 (Amounts based on 100 gallons of spray mixture) 



Caustic Soda 



Reduction of Soap Consumption 



Difference 



1. The amounts in this table were computed on the basis of eight 

 pounds of soap per 100 gallons. Soap and soda valued at 16c a pound. 



2. The results from the use of caustic soda cannot be estimated 

 alone by the reduction in soap consumption. Its value as an aid in 

 emulsifying oil must be considered although it is difficult to estimate. 



Oil Emulsions and Hard Water 

 Petroleum oil is usually emulsified with the aid of fish-oil or laundry 

 soap. It is a well known fact that the use of hard water in the house- 

 hold and laundry hinders the formation of lather. Similarly, hard 

 water destroys oil emulsions. In both instances, the soluble soda 

 and potash soaps, which are unaffected chemically by soft waters, 

 react with the calcium and magnesium salts in the hard water and 

 form an insoluble soap. This insoluble soap is of no value in making 



