42 II. Gruener — Iodometric Determination of Nitrates. 



facts that this portion of the well section belongs to the Mio- 

 cene series, and in all probability to the upper part of the 

 same. 



The .above conclusions may be stated diagrammatically as 

 follows : 



Sample Nos. Depth in feet. Geological horizons. 



1-10 46- 458 Pleistocene. 



10-44 458-1511 Doubtful. 



44-61... 1511-2153 Upper Tertiary. 



61-91 2153-2920. Miocene (Upper) 



Probably some of the strata between the depths of 458 and 

 2153 feet were deposited in Pliocene times, but not a trace 

 of a species characterizing that series has been found. 



Art. VI. — On the Iodometric Determination of the Nitrates ; 

 by Hippolyte Gruener. 



[Contributions from the Kent Chemical Laboratory of Yale College — XXIV.] 



De Kontnck and Nihoul* describe a method for the iodo- 

 metric determination of nitrates, in which the decomposition 

 of the nitrates is effected by the action of gaseous hydrochloric 

 acid, the gases evolved being passed into potassium iodide ; but 

 the method is a cumbersome one In a former paperf by 

 Professor Gooch and myself a method was described accord- 

 ing to which nitrates were decomposed successf ally and easily 

 by a solution of manganous chloride in hydrochloric acid, the 

 products of decomposition being passed into potassium iodide, 

 and the liberated iodine titrated with sodium thiosulphate. 

 The ease with which hydriodic acid has been applied in this 

 laboratory as a reducing agent in the determination of arsenic, 

 chloric and antimonic acids;): has suggested its application for 

 the same end to nitric acid, and the present paper is the 

 account of attempts in this direction. 



The Action of Phosphoric Acid and Potassium Iodide 

 upon Nitrates. — The decomposition of the last traces of nitrates 

 in presence of potassium iodide and sulphuric acid does not 

 occur except at very great concentrations, and, as at great con- 

 centrations sulphuric acid in presence of hydriodic acid itself 

 liberates iodine, the use of sirupy phosphoric acid to bring 

 about the required decomposition naturally suggested itself. 

 Various attempts to simplify the process while still registering 



*Zeitschr. f. angewandte Chemie. 1890, p. 477. 



f This Journal, vol. xliv, p. 117. 



% This Journal, vol. xl, p. 66 ; vol. xlii, p 220 ; vol. xlii, p. 213. 



