﻿178 INDIANA UNIVERSITY STUDIES 



With each 100 gms. of potassium perchlorate, 60 cc. of con- 

 centrated sulphuric acid should be used. This is 50 per cent in 

 excess of the amount of acid to form KHSO4. Less sulphuric acid 

 than this amount causes spattering of the contents of the flask and 

 requires too high a temperature near the end of the distillation. 

 More sulphuric acid than this amount increases foaming. 



Steam should be passed into the contents of the flask during the 

 distillation at such a rate that no crystals (HCIO4. H2O) will form 

 in the condenser. An excess of steam causes spattering and 

 lengthens the time of distillation. 



A vacuum of from 6 to 10 cm. of mercury should be maintained. 



At the end of an experiment, the flask should be heated until 

 sulphuric acid distihs and condenses upon the sides of the flask. 

 Thus all the potassium perchlorate is acted upon. This will in- 

 crease the amount of sulphuric acid as well as the quantity of 

 perchloric acid in the distillate. 



Considerable amounts of sulphuric acid always pass over with 

 the perchloric acid. The sulphuric acid may be precipitated by 

 adding the correct amount of barium carbonate to the distillate. 

 All of the sulphuric acid can be rem^oved by redistilling the crude 

 perchloric acid. Of course steam should be passed through the 

 distilling flask during the distillation. 



The yields of perchloric acid vary from 88 to 98 per cent., 

 depending upon how well the conditions of the experiment have 

 been followed. 



About 200 gms. of potassium perchlorate is the maximum 

 amount that can be distilled rapidly from a flask of 1000 cc. capacity. 



Attempts to read the temperature in the distilling flask were 

 not successful. The stem of the thermometer and the inside of 

 the flask always becam.e covered with potassium perchlorate due 

 to spattering. The thermometer scale was visible only near the 

 end of the experiments. 



The time when all perchloric acid is out of the distilling flask 

 can be told by the cUsappearance of solid material (KCIO4) and the 

 change from foaming or bubbling to a condition of quietness with 

 occasional bumping. 



Care must be taken to prevent the contents of the distilling 

 flask from sucking back into the steam flask. This can be done by 

 putting upon the steam flask a stop-cock which can be opened into 

 the air. 



There is no danger of an explosion. In all of these experiments 

 there was no indication of an explosive decomposition. 



