NATURE AND SOITRCE OF SPRAYING MATf:RIALS. 187 



SODIUM CARBONATE {formvla NagCOs-lOHgO). 



Sodium carbonate, sal soda, or washing; soda is nsod in making car- 

 bonate of copper from the sulphate of copper and in preparing the 

 modified eau celeste. As obtained in the market it is in colorless, 

 monodinic crystals, showing a strongh' alkaline reaction to litmus 

 paper. When exposed to the air much of the water of crvstallization 

 is lost from the crystals, which rapidly eifloresco or slake to a white 

 powder. When perfect, nearly two-thirds of the crystals, by weight, 

 is water. 



Carbonate of soda dissolves in 1.6 parts of water at 59° F. and in 

 0.2 part of boiling water. When a solution of sal soda is added to 

 the solution of copper sulphate in making copper carbonate, or to an}^ 

 other acid solution, a decided eft'ervescence takes place, so that in 

 making the copper carbonate the two solutions used should be united 

 slowly or they may overflow the containing vessels. The more com- 

 mon impurities found in sodium carbonate are sodium chloride 

 (common salt) and sodium sulphate (Glauber's salt). These impurities 

 are due to the source and manner of manufacture of the sal soda, but 

 are not usually present in the latter in suthcient amount to require 

 attention in the spray work Ix'ing considered. 



The sources of sodium carbonate are somewhat numerous, but the 

 commercial supply of to-day is derived mainly from common salt or 

 from natural deposits of the carbonate. In nearly all arid countries 

 carbonate of soda is frequently found in the soil in such quantities as 

 to be injurious to vegetation. West of the Missouri River large accumu- 

 lations of the different soluble salts of the soil arc frequently met 

 w^ith. In the East such accumulations are prevented by the greater 

 rainfall, the salts being eventually washed from the soil and carried to 

 the sea, but in the West they often coat the ground, appearing white 

 or black, and are known as " alkali beds," owing to the frequent pres- 

 ence of stronolv alkaline salts, such as sal soda. The most abundant 

 constituents of these deposits are sodium sulphate, sodium chloride, 

 and sodium carbonate. The sodium chloride and sodium carbonate are, 

 when in excess, so injurious to vegetation as to constitute a leading 

 Imne of the horticulturist of the western half of the United States. In 

 the great plateau region between the Rocky Mountains and the Sieirra 

 Nevada and Cascade ranges are vast stretches of alkaline soils, the 

 soluble salts of which accumulate in lakes and along water courses 

 through the drainage of the winter rains. During the long, dry sum- 

 mer these waters evaporate to a considerable extent, leaving the salts 

 deposited along the margins of the lakes and rivers.^ In some cases 

 these deposits of alkali are composed largely of sodium carbonate, and 

 in several instances, after passing through a simple purifying process. 



^These deposits are very well shown in the illustrations of Bull. No. 14, Division 

 of Soils, U. S. Dept. of Agr. 



