44 H. Gruener — lodometric Determination of Nitrates. 



of water. The iodide was introduced dry or in solution 

 according to the bulk of water allowable. This mixture was 

 boiled a moment to drive out all air, the phosphoric acid was 

 then added, and carbon dioxide was passed as described, the 

 receiver containing the arsenious oxide and the trap being 

 already in position. It had been found that all but a trace of 

 iodine was caught in the first receiver, so that the rubber stop- 

 per closing it could do no harm. When large amounts of 

 nitrate were used the clots of solid iodine settling out in the 

 receiver were dissolved by means of a crystal or two of potas- 

 sium iodide. The solution in the retort was boiled until it 

 was clear that all the iodine had distilled over, and usually 

 until the boiling in the retort had ceased. It was found advis- 

 able to empty the retort so soon as it was cool enough, else the 

 phosphoric acid became unmanageable. The retort after each 

 experiment was washed out with ammonia and water. 



The results of these first experiments are shown in Table I. 



Table T. 









Water added to 















10 cm 3 of phos- 











KN0 3 



KI 



phoric acid, 



KS0 8 



Error in 



Error in 





taken. 



taken. 



sp. gr. T7. 



found. 



KNO3. 



Htf0 8 . 





Series 1. 















grm. 



grm. 



cm 3 . 



grm. 



grm. 



grm. 



1 



00005 



•2 



2 



0-0009 



0-0004 + 



0-0002 + 



2 



00010 



■2 



2 



0-0012 



0-0002 + 



0001 + 



3 



00020 



•2 



2 



0-0021 



0-0001 + 



00001 + 



4 



0-0050 



■2 



2 



0-0055 



0-0005 + 



00003 + 



5 



o-oioo 



•2 



2 



0-0093 



0-0007- 



0004- 



6 



o-oioo 



•2 



2 



0-0103 



0-0003 + 



0-0002 + 



7 



00200 



•3 



3 



0-0216 



0-0016 + 



0-0010 + 



8 



0200 



•3 



3 



00192 



0-0008- 



0-0005- 



9 



0-0200 



•3 



3 



00205 



0005 + 



0-0003 + 



10 



0-0200 



•3 



3 



0-0205 



0-0005 + 



0-0003 + 



11 



00500 



•5 



6 



0-0496 



00004- 



0-0002 — 



12 



00500 



•5 



6 



0-0499 



0001 — 



0-0001- 



13 



0-0300 

 Series 2. 



•5 



4 



0-0293 



0-0007- 



0-0004- 



14 



0-0616 



1-5 



1 



0-0682 



0-0066 + 



0-0039 + 



15 



0-0570 



2-5 



1 



0-0643 



0-0073 + 



0-0045 + 



16 



0-1030 



1-1 



1 



0-1061 



0-0031 + 



0-0018 + 



17 



0-1062 



1-1 



1 



0-1197 



0-0135 + 



0-0081 + 



With one or two exceptions the results of Series 1 are fairly 

 good. Those of Series 2 are very bad The only essential 

 difference between the two series is in the dilution of the 

 phosphoric acid used. In the first series there is always 

 enough water present to make the specific gravity of the phos- 

 phoric acid no higher than 1*6 for small amounts of iodide 

 and nitrate, and lower than that number when these amounts 

 are increased. The suggestion is obvious that dissociation of 



