﻿174 



INDIANA UNEVERSITY STUDIES 



acid was formed. Rapid distillation was also essential, for in one 

 experiment, where the heating extended over a period of two hours, 

 the yield was only 20 per cent. 



The distillation mider reduced pressure gave much better yields. 

 A tubulated retort was used as the distilhng vessel. Syrupy phos- 

 phoric acid was employed to make the ground glass stop-cock air- 

 tight. As there was no way of introducing a thermometer into the 

 retort, temperature readings could not be made. The hot perchloric 

 acid vapors attacked the cork stopper which connected the retort to 

 the condenser, especially when no water was added to the mixture 

 in the retort. The neck of the retort was bent downwards so that 

 potassium perchlorate which spattered during the distillation w^ould 

 not be carried over into the receiver. A Chapman water pump was 

 used to produce the reduction in atmospheric pressure. As water 

 pressure was variable, the vacuum was continually changing. A 

 Bunsen rubber valve/ used to prevent water being drawn into the 

 apparatus from the pump, was placed in the train of apparatus 

 nearest the water pump. In each of the experiments given in the 

 following tables, ten grams of potassium perchlorate were used. 



Cc.H,S04.* 



Cc. H,0. 



Pressure, in cm. 

 of Hg. 



Distillate 

 Gran 



H,S04. 



Contained 

 IS of 



HCIO4. 



Yield in 

 Per Cent. 



5 



2.5 



5 



- 9 



0.89 



6.16 



84.9 



5 



5 



8 



-11 



1.04 



5.64 



77.7 



7.5 



2.5 



13 





0.85 



6.25 



86.2. 



7.5 



5 



10 



-13 



0.84 



6.5 



89.6 



7.5 



7.5 



10 



-12 



0.64 



6.5 



89.6 



, 10 



0 



3 



- 7 



0.41 



6.2 



85.2 



10 



0.5 



9 



-11 



0.5 



6.7 



92.4 



10 



1 



8 



-10 



0.51 



6.7 



93.3 



10 



2.5 



9 



-11 



0.45 



6.8 



93.4 



10 



5 



10 



-11 



0.56 



6.5 



90.3 



10 



7.5 



10 



-11 



0.58 



6.4 



88.9 



10 



10 



10 



3-10.6 



0.47 



6.3 



87.3 



15 



5 



7 



5- 8.9 



0.71 



6.8 



94. 



* Four cc. of concentrated sulphuric acid is the theoretical amount to form KHSOj with 10 grams 

 of potassium perchlorate. 



^ This valve was made from two pieces of 1 cm. diam. glass tubes. One piece was drawn out so 

 that it would pass part way into the other piece. Over the small end of this glass tube was placed a 

 short piece of rubber tubing which was then plugged at the open end. A slit, about 0.5 cm. long, was 

 made in the rubber at a place near the plug. The two pieces of glass were then placed together, the 

 one part way into the other, and the .joint was covered with a rubber tube. This valve was extremely 

 satisfactory and it is reconamendcd for use in all vacuum distillations. 



I 



