Gooch and Gruener — Iodometric Determination, etc. 117 



Aet. XYII. — A method for the Iodometric Determination 

 of Nitrates ; by F. A. Gooch and H. W. Gruener. 



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



It has been shown by DeKoninck and Nihoul* that nitrates 

 may be decomposed completely by the prolonged action of 

 gaseous hydrochloric acid, and determined with accuracy by 

 measuring the iodine set free when the products of decomposi- 

 tion, carefully kept from atmospheric contamination, act upon 

 potassium iodide. These investigators recognized the diffi- 

 culties attending the use of gaseous hydrochloric acid in analyt- 

 ical processes, and endeavored unsuccessfully to substitute the 

 strong aqueous solution for the gaseous acid. The work to be 

 described in the following account was performed in the search 

 for a simpler method for the iodometric determination of 

 nitrates. 



According to a process recently developed in this laboratory! 

 chloric acid may be determined with the greatest ease. It was 

 shown that in the interaction of a chlorate with potassium 

 iodide, arsenic acid, and sulphuric acid, in regulated quantities 

 in aqueous solution and at the boiling temperature, the first 

 action of the hydriodic acid set free from the iodide by the 

 sulphuric acid is upon the chloric acid, and that not until this 

 action is completed is the arsenic acid attacked and reduced 

 with the simultaneous liberation of a corresponding amount of 

 iodine. If the arsenic acid is taken in quantity sufficient to 

 insure the final decomposition of the entire amount of iodide 

 present, the arsenious acid found at the end of the action is an 

 exact measure of the amount of iodide which escaped the 

 action of the chlorate ; and, the quantity of iodide originally 

 taken being known, the amount acted upon by the chlorate, 

 and so the amount of the chlorate itself, becomes known. The 

 arsenious acid is determinable with great accuracy iodometri- 

 cally, and the chief advantage of the process lies in the fact 

 that the titration is made upon the residue, and that, no collec- 

 tion of the distillate being necessary, the sole apparatus em- 

 ployed in the process proper is an Erlenmeyer beaker and a 

 bulbed tube hung in its neck as a trap to prevent mechanical 

 loss. 



This process we endeavored to apply to the determination of 

 nitrates, but under none of the many variations of form and 

 changes of conditions under which we tested it, were we able 

 to secure complete decomposition of the nitrate without so 



*Zeitschr. fur angewandte Ctaemie, 1890, p. 477. 

 f Gooch and Smith, this Journal, vol. xlii, p. 220. 



