SCHMIDT'S PROCESS 411 



40 cubic centimeters of ferrous chlorid solution containing about 

 200 grams of iron to the liter, and also an equal volume of hydro- 

 chloric acid of i.i specific gravity. The side tube is also filled 

 up to the funnel with the acid. The contents of the flask are 

 boiled until all air is expelled, which can be determined by hold- 

 ing a test-tube filled with water over the end of the delivery 

 tube. The solution containing the nitrate is next placed in the 

 funnel, the pinch-cock opened and the liquid allowed to run into 

 the flask by means of the partial vacuum produced by stopping 

 the boiling and allowing the mercury to rise in the delivery tube. 

 All the solution is washed into the flask by successive rinsings 

 of the funnel with hydrochloric acid, being careful to allow no 

 bubble of air to enter. The contents of the flask are again 

 raised to the boiling-point and the nitric oxid evolved collected in 

 the nitrometer. The solution examined should contain enough 

 nitrate to afford from 60 to 80 cubic centimeters of gas. With- 

 out refilling the flask, from eight to nine determinations can be 

 made by regenerating the ferrous chlorid by treatment with zinc 

 chlorid. Care must be exercised not to add the zinc chlorid in 

 excess, otherwise ammonia and not nitric oxid will be produced. 

 The side tube and funnel must also be carefully freed from zinc 

 chlorid by washing with hydrochloric acid. 



356. Schmidt's Process. In the case of a water, or the aque- 

 ous extract of a soil, according to the content of nitric acid, 

 from 50 to loo cubic centimeters are evaporated to 30 cubic cen- 

 timeters, and the residue sucked into the generating flask of the 

 apparatus, Fig. 27, and, with the rinsings with distilled water, 

 evaporated again to from 20 to 30 cubic centimeters, and the flask 

 then connected, as shown in the figure, to a schiff measuring 

 apparatus B. 45 This apparatus is previously filled to i with mer- 

 cury, and the bulb g connected with k by a rubber tube. 



The apparatus is then filled with a 20 per cent, caustic soda 

 solution previously boiled and still warm, until the bulb g is 

 partially filled when raised a little above the cock h. Then h is 

 closed and g held, by an appropriate support, on about the 

 same level with h. The cock at b is then closed and e opened. 

 45 Apotheker Zeitung, 1890, 5 : 287. 



