﻿INDTA^s^A UNFYEESTTY STUDIES 



This table shows that excellent yields were obtained hy using 

 an excess of sulphuric acid. A httle water was apparently helpful, 

 but some very good results were obtained with only the water that 

 was present in the imperfectly dried flask, and the air dried potas- 

 sium perchlorate. In these experiments, the vacuum was much 

 better than in previous experiments; this was partly responsible for 

 the increased yields. 



These excellent yields could not be duplicated when using larger 

 quantities of potassium perchlorate. The distillation would pro- 

 ceed quietly for a while, then decomposition would begin. Gases 

 would be given off which would weaken the vacuum and this in 

 turn would cause more decomposition. The vacuum could be re- 

 covered only by removing the flame and by allowing the flask to 

 cool. In most cases, when the flask was heated again, decomposi- 

 tion would begin and the vacuum would be destroyed as before. 

 The results of some of the experiments are given in the following 

 table. One hundred gms. of potassium perchlorate was used in 

 each experiment. 



Cc. H,S04. 



Cc.H^O. 



Minimum 

 Pressure in 

 cm. Hg. 



Time of 

 Distillation. 

 Hours. 



Yield, 

 Per Cent. 



60 



5 



7 



2.2 



70.3 



60 



6 



8 



2.7 



63.9 



60 



20 



4 



1.6 



61.9 



In all of these experiments the distillation seemed to be suc- 

 cessful for the first 20 to 30 minutes. If the lack of water was the 

 cause of the trouble, the addition of a large amount of water at the 

 beginning of the experiment was useless, because the excess of water 

 always distilled out before any perchloric acid came over. The 

 addition of water through a separatory funnel to the contents of 

 the flask during the distillation caused too vigorous a reaction with 

 the hot sulphuric acid. A mixture of equal parts of sulphuric acid 

 and water added in five portions of 5 cc. each during the distillation 

 raised the yield to 79.7 per cent. The vaccuum was also much 

 easier to maintain during this experiment. The solution of the 

 problem was to pass steam into the contents of the flask during 

 the course of the distillation. The neck of the distilling flask was 

 made six inches longer by sealing on a glass tube of the proper 

 diameter. A rubber stopper could be used in this flask since its 

 position in the neck was so far from the heat that the perchloric 



