42 Gooch and Curtis — Halogen Acids upon Vanadic Acid. 



In continuing the study of this reaction we have thought it 

 desirable to try to effect the removal of the chlorine and to 

 complete the reaction by bubbling a current of gaseous hydro- 

 chloric acid through the cooled residue of a single treatment 

 by boiling. Under these conditions the hydrochloric acid must 

 always be at the concentration of activity, though the removal 

 of the chlorine must be slow since the current of gas should not 

 be rapid enough to cause mechanical loss from the mixture. 



The apparatus used in these experiments was similar to that 

 employed in the former work to which reference has been 

 made, and is shown in the accompanying figure. We have 



used as the source of vanadic acid for the experiments to be 

 described immediately, and throughout this paper, ammonium 

 vanadate of known purity, standardized by the method of 

 Holverscheit.* 



In every experiment approximately 0*1 gm. of ammonium 

 vanadate was first introduced into the reduction flask B. The 

 air was expelled from the apparatus by carbon dioxide from 

 the generator, the receiver C being charged with hydrochloric 

 acid and the trap g with water. Concentrated hydrochloric 

 acid (15 cm3 ) was admitted through the stoppered funnel A, and 

 the mixture was boiled. The deep red color produced when 

 the acid was first added, gradually passed through green to 

 blue. The flask was allowed to cool, carbon dioxide being 

 admitted to fill the partial vacuum, and surrounded with ice. 

 Hydrochloric acid gas was passed into the reduction flask, at 

 the rate of one or two bubbles a second, through the solution 

 for periods varying from \ to 112 J- hours, the solution turning 

 brown at first and then changing to green or blue, according to 

 the length of the period. For continuing the flow of gas for 

 long periods small Kipp generators set up with sublimed ammo- 

 nium chloride in large lumps, and concentrated sulphuric acid, 

 were found very convenient, a single charge serving to keep up 

 the flow continuously over night. 



*Inaug. Dissert., Berlin, 1890, p. 48. 



