142 MANURES. VII. 



chlorides, iodates, and borates of calcium, magnesium, and 

 sodium. There are also traces of chromium, existing probably 

 as calcium chromate.* 



Pure sodium nitrate is a white crystalline salt containing 

 no water of crystallization, but generally holding a small 

 quantity of hygroscopic moisture. Indeed, in moist air it is 

 deliquescent. In addition to its use as a manure it finds 

 application in the arts as a source of nitric acid and in the 

 manufacture of gunpowder and of potassium nitrate. 



The product supplied for agricultural purposes is supposed 

 to contain 95% or over of real sodium nitrate and thus to 

 yield more than 15'6% of nitrogen. Being extremely soluble and 

 diffusible it is at once available to plants and should only be 

 applied when the crop is sufficiently grown to be capable 

 of assimilating it ; otherwise, since it is not retained by any 

 constituent of the soil, considerable loss in the drainage may 

 occur. 



In 18971 Sjollema found that in many cases in Holland and 

 Belgium, rye was damaged by the application of "nitrate of 

 soda." On investigation he found that the injury was due to 

 the presence, in the nitrate, of perchlorates. In a number of 

 samples examined he found from 0*14 to 6'79% of perchloric 

 acid (C10 4 ). By direct experiment he showed that potassium 

 and sodium perchlorates retard germination and cause the 

 leaves of plants to which they are applied to become yellow. 



Other investigations have confirmed these results; e.g., 

 Zaharia as a result of an examination of 206 samples of Chili 

 saltpetre at Halle found one sample containing between 5 and 

 6%, one 3 to 4%, three 2 to 3%, eleven 1-5 to 2%, thirty-nine 

 1*0 to 1'5%, while the remaining 151 contained less than 1% 

 of perchlorate J . 



Maercker in 107 samples of Chili saltpetre found 



Nitrogen. Sodium nitrate. Sodium perchlorate. 



Maximum ... 15*6% 94-7% 5'64% 



Minimum ... 13-8% 83-8% 0-27% 



Mean ... 15-1% 91-6% 0'94% 



* Buchanan, Jour. Soc. Chem. Ind. 1893, 128. 



t Annales Agronomiques 1897, 328; Jour. Chem. Soc. 1897, abst. ii., 585. 



J Hied. Centr. 1899, 511; Jour. Chem. Soc. 1899, 799. 



Jahresbericht iiber Agricultur-Chemie 1899, 105. 



