Sept. 10, 1917 



Formation oj ''Black Alkali" 



545 



nia, Colorado, and Utah Experiment Stations. Owing to the interest 

 in this subject and in the injurious effects of continued applications of 

 sodium nitrate as a fertilizer to Citrus groves, the reaction of sodium 

 nitrate and calcium carbonate was first considered. 



Solutions of sodium nitrate in graduated concentrations (given in 

 Table I) were prepared with boiled distilled water. These were put in 

 shaker bottles, with about i gm. of calcium carbonate in each bottle, 

 tightly stoppered, and shaken for several days, or until they had reached 

 equilibrium. Special effort was made to keep carbon dioxid out of the 

 solution, but the opening of the bottle for the purpose of titrations, etc., 

 made it impossible to keep it entirely out. As the saturation point of 

 sodium nitrate increases noticeably with an increase of temperature, 60 

 per cent was taken as approximately representing the average condition 

 of saturation. 



When equilibrium was reached, aliquots were drawn off and titrations 

 made for carbonates, with phenolphthalein as an indicator. The titra- 

 tion in distilled water, which was, of course, due to calcium carbonate 

 was subtracted from each of the other titrations where sodium nitrate 

 was present. This difference was then calculated as sodium carbonate. 



These results are shown in Table I and figure i. 



Table I. — Reaction between sodium nitrate and calcium carbonate 



Solutions of sodium chlorid and sodium sulphate and mixtures of 

 equal parts of sodium chlorid and sodium sulphate were prepared and 

 run in the same way as with the sodium nitrate. These results are shown 

 in Tables II, III, and IV and figure i. 



Table II. — Reaction between sodium chlorid and calcium carbonate 



