﻿MATHERS: PEHCHLORIC ACID 



177 



acid fumes did not attack it badly. During a vigorous distillation 

 some solid potassium perchlorate would spatter into the neck of 

 the flask above the side arm and would not be acted upon by the 

 sulphuric acid. This decreased the yield. No way was found to 

 overcome this trouble. If the supply of steam was deficient, de- 

 composition would begin and the yield would be lowered. Enough 

 steam should be used to prevent the formation of crystals 

 (HCIO4. H2O) in the condenser. The evolution of gases, which 

 destroy the vacuum, shows that too little steam is being used. 

 An excess of steam does not lower the yield. If too small a flask 

 is used there is some trouble with foaming. The maximum quantity 

 of potassium perchlorate for a 1000 cc. flask is about 200 gms. 

 The following table shows the results: 



Cc. 



SO4. 



Gms. 

 KCIO4 



Cc. of 



H2O as 

 Steam. 



Time. 

 Hours. 



Pres- 

 sure 

 Hg. 



Distillate 

 Contained 

 Grams of 



Yield, 

 Per 

 Cent. 



Remarks. 







H2SO4 



HCIO4 





60 



100 



150 



1.4 



6-8 



19 



62.7 



86.6 



Vacuum poor twice. 



60 



100 



200 



1 



6-8 



14.8 



67.7 



93.4 



Good vacuum. 



60 



100 



650 



7.2 



6-7 



23.6 



65.7 



90.6 



Vacuum poor twice. 



60 



100 



500 



1.6 



6-9 



26 



68.8 



94.9 



Good vacuum. 



50 



100 



500 



1.6 



8- 



18.7 



57.8 



79.8 



Vacuum poor twice. 



70 



100 



300 



0.7 



8-10 



25.7 



71.8 



99 



Good vacuum. 



240 



400 



1150 



3.8 



8-16 



66 



255. 



88 



Vacuum never good. 



180 



300 



550 



1.3 



6-9 



33 



190. 



87 



Much KCIO4 in neck. 



Much trouble was encountered with low water pressure while 

 performing these experiments. It was difficult to maintain a pres- 

 sure below 10 cm. of mercury for a long period of time. It was 

 important to have enough steam at all times. Any weakening of 

 the vacuum immediately stopped the boiling of the steam flask, 

 and this, of course, soon started decomposition in the distilling 

 flask. Careful watching could not altogether avoid trouble if 

 the water pressure was unsteady. The speed of distillation had 

 no influence upon the yield and needed regulation only to avoid 

 foaming into the condenser. 



Summary and Conclusions. This research gives the results of 

 experiments to determine the best conditions for the preparation of 

 perchloric acid by distilling potassium perchlorate with sulphuric 

 acid. 



[3—28886] 



