340 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 15 



lead may produce a soluble arsenical dangerous to foliage. (2) By 

 physical reactions, such as the breaking of oil or cresol emulsions in 

 hard waters, which free the chemicals held in suspension and de- 

 stroy the value of the mixture. We now recognize such dangerous or 

 neutralizing reactions when hard and perhaps alkaline waters are com- 

 bined with petroleum or cresol emulsions acid lead arsenate, fish -oil 

 or whale-oil soap and nicotine sulphate.^ The formation of a precipi- 

 tate in combining lime-sulfur solution with hard water has also been 

 noted and further study of this subject may reveal other dangerous 

 or undesirable combinations. 



Water containing considerable quantities of sodium salts, including 

 chlorids, bicarbonates and carbonates is classified as "alkaline." When 

 considerable proportions of magnesium or calcium either in the bicar- 

 bonate or sulphate form are present the water is termed "hard." Wa- 

 ter hardness is of two types, "temporary" and "permanent." The 

 first is the result of bicarbonate of lime or magnesium held in solution 

 by an excess of carbonic acid. This form is largely broken up b}' boiling, 

 the carbonic acid being freed and the normal carbonates of lirne and 

 magnesium precipitated. Permanent hardness is the condition result- 

 ing from the presence of sulphates or chlorids of lime and magnesium 

 and to the carbonates still held in solution after boiling. This form 

 cannot be overcome by heating. Both types can, however, be parti- 

 ally counteracted by the addition of chemical water softeners. 



In this paper no distinction is made between the various kinds of 

 hardness, whether due to bicarbonate, sulphate or chlorid of calcium 

 and magnesiimi, as their reaction with soap is somewhat similar. 

 Neither will there be any distinction drawn between temporary and 

 permanent hardness of water, the total hardness alone being estimated. ^ 



Determination of Hardness 

 The soap consuming or destroying power of the water sample was 



'Imes, Marian, "Cattle Lice and How to Eradicate Them," U. S. Farmers' Bui. 

 909 p. 14. 



-A survey was made in 1919 of a typical horticultural region in California to de- 

 termine the distribution and degree of hardness existing in the local waters. Samples 

 of water were collected from the entire district, the degree of hardness determined 

 by tests with a standard soap solution, and modified formulas for making oil emul- 

 sions worked out for each type of water. A map of the surveyed region was then 

 made, giving the location of each well tested. Surveys of this nature, giving definite 

 information about local water supplies, will enable the orchardist to choose spray 

 materials suitable to his water supply. The manufacturer of insecticides will find 

 this information of value in preparing and marketing his materials, and to the horti- 

 cultural officer it will serve as a guide for his recommendations and will assist in 

 interpreting orchard troubles. 



