THE SYNTHESIS OF ARGENTIC NITRATE. 



51 



\ 



tical. A sufficient quantity of purest nitric acid mixed with half its 

 volume of distilled water was poured in from the platinum crucible into 

 which it had just been distilled. The cover of the desiccator was replaced, 

 but its stopper was first removed, and covered with a watchglass and a 

 clean beaker. The apparatus was now kept all night in a warm place, 

 between 40 and 50 C. ; thus the silver when dissolved remained in solu- 

 tion, though the volume was restricted to 2 cm. of solution per gram of 

 nitrate. In the morning the process was found to be complete. After 

 washing down the neck with a few drops of freshly distilled water, the 

 flask was placed in the oven as before. The desiccator was washed with a 

 little water, the washings being tested for silver in the nephelometer ; if 

 any had been found it might have been feared that more had escaped, but 

 as no trace was ever found, it was inferred that the 

 long inclined neck had caught all the spray. 



Attention is now called to the apparatus for evapo- 

 ration. 1 The main feature of this was the combined 

 delivery tube for the air current and hood for the 

 protection of the contents of the flask. This hood H 

 with its ingress and egress tubes, / and E, is shown 

 in the diagram (figure 1). The dry air used to 

 sweep out the aqueous and nitrous vapors entered 

 from the purifying train at G, where connection was 

 made by a well-ground joint; passing through the 

 tube /, it escaped into the body of the flask and out 

 through its neck. A side tube, E, was attached to 

 H for connection with a water-pump. The flask 

 rested on a triangle of platinum wire attached to a 

 glass tripod, and the whole was placed in a 1.5-liter 

 beaker which served as the oven. A sand-bath en- 

 abled this to be kept at any desired temperature. 

 The cover of the beaker was of sheet copper, pierced 

 with three holes, for the tubes / and E, and for the 

 thermometer. As no nitrous fumes escaped into 

 the oven, this cover remained intact. In the prelimi- Fig. I. -Apparatus for Ev ?P o- 



. , , . - rating Aqueous Solutions. 



nary trials the extra tube Q was lacking, the tube Section about half actual size 

 / being extended to take its place. The part which 

 had projected into the body of the flask was treated 

 with hot dilute nitric acid and investigated for silver 



H 



by platinum wire, serv- 

 ing as air-nozzle. 



1 In passing it might be, noted that one of us used a somewhat similar arrange- 

 ment for evaporating solutions of sodic sulphate fifteen years ago (Proc. Am. 

 Acad., 26, 258 (1891). 



