544 



Journal of Agricultural Research 



Vol. X, No. It 



Hilgard, working with Webber, and later with Jaffa, determined the 

 amounts of sodium bicarbonate formed when a stream of carbon dioxid 

 was passed through solutions of sodium sulphate and sodium chlorid 

 in contact with an excess of calcium carbonate (6, p. 449-451). 



The solubility of calcium carbonate in pure water is about 10 parts 

 per million, while in the presence of carbon dioxid its solubility is in- 

 creased many times. In boiled distilled water calcium carbonate may 

 be titrated, phenolphthalein being used as an indicator. However, the 

 amount of carbon dioxid that usually occurs in ordinary distilled water 



is sufficient to make 

 such a titration impos- 

 sible. In such a case 

 the titration with 

 methyl orange as an in- 

 dicator will, of course, 

 give the amount of 

 lime. 



In this investigation 

 the results of the reac- 

 tions of sodium nitrate, 

 sodium chlorid, and so- 

 dium sulphate with cal- 

 cium carbonate, which 

 react with phenolph- 

 thalein, are figured as 

 sodium carbonate, 

 while all titrations 

 which react with 

 methyl orange are fig- 

 ured as sodium bicar- 

 bonate. While it is re- 



o s /o /5 so es so 35 ^yo '^s so 55 eo 

 ^=^£/? cavr A/aAO^j Ae>c/ o^ /va^ so^ 



Fig I. — Graphs of the sodium carbonate formed from reaction of cal- 

 cium carbonate (solid phase present) with sodiiun chlorid, sodium 

 nitrate, or sodium sulphate. 



alized that this is not strictly accurate, from the standpoint of a physical 

 chemist, yet it is sufficiently accurate for the purposes of this investigation. 



Occasional samples of a salt, especially sodium chlorid and sodium sul- 

 phate, were found to be slightly acid. This caused a great deal of trouble 

 until the cause was discovered. Afterwards all salt solutions were neu- 

 tralized with sodium hydrate before beginning the experiments. 



This work was done at Riverside, Cal., and apparatus for the accurate 

 control of temperature was not at hand. The work was carried on at 

 room temperatures, with a considerable variation between night and day. 

 The determinations, therefore, must not be understood as solubility 

 measurements, but simply laboratory studies to be applied to field con- 

 ditions near by. 



The formation and the accumulation of nitrates and their effect upon 

 plants has recently been given much attention, especially by the Califor- 



