C. F. Roberts — Estimation of Chlorates and Nitrates. 231 



Art. XXXI Y. — On the Estimation of Chlorates and Nitrates, 

 and of Nitrites and Nitrates in one operation / by 

 Charlotte F. Koberts. 



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



A recext paper by Gooch* and Gruener has shown that 

 nitrates may be estimated most accurately by treatment with 

 manganese chloride, the chlorine thus liberated being col- 

 lected in potassium iodide, and the amount of iodine set free 

 determined by titration with sodium thiosulphate. In a late 

 number of this Journal, f I have shown that good results are 

 also obtained by treatment of the nitrate with ferrous chloride, 

 and collecting and measuring the nitric oxide evolved over 

 sodium hydroxide with the apparatus described and pictured 

 in that article. 



This apparatus consists essentially of a small retort fitted 

 with a hollow, ground-glass stopper prolonged beneath in a 

 tube, and joined above with two branching tubes through one 

 of which carbon dioxide may enter, and the other of which is 

 attached to a funnel-tube with stop-cock, through which 

 liquids may be introduced without admitting air. The retort 

 is connected with a small condenser, which in turn is attached 

 to a Will and Yarrentrapp tube containing potassium iodide, 

 and this with a Hempel's burette containing a strong solution 

 of sodium hydroxide. In the experiments described, the 

 potassium nitrate was introduced into the retort, carbon di- 

 oxide passed through until the air was completely driven out, 

 and then ferrous chloride added through the funnel-tube. 

 After heating, and passing a current of carbon dioxide through 

 the apparatus, the volume of gas unabsorbed by sodium 

 hydroxide was measured at the observed temperature and 

 pressure, and from this the weight of potassium nitrate was 

 calculated. This is merely a special form of a very common 

 method of estimating nitrates, but the apparatus is in a form 

 which can be conveniently handled and which readily adapts 

 itself to other uses beside the simple determination of nitrates. 

 In a mixture of chloric and nitric acids, for example, it be- 

 comes possible by a combination of the two above-named 

 methods for estimating nitrates, and the use of the apparatus 

 described, to determine in one operation the amounts of each 

 present. A method for the determination of chlorates which 

 has long been in common use consists in treatment with hydro- 



* This Journal, vol. xliv, 117. 

 f Vol. xlvi, p. 126, August, 1893. 



