THE ANALYTICAL PROCESS 587 



to a thick, sirup-like consistency, again dissolved in hot water 

 and evaporated, with continued stirring, till all hydrochloric acid 

 has been expelled and the fumes of perchloric acid appear. Fur- 

 ther loss of perchloric acid is to be compensated for by addition 

 of more of the reagent. The cold mass is then well stirred with 

 about 20 cubic centimeters of wash alcohol (97 per cent, alcohol 

 containing 0.2 per cent, by weight of pure perchloric acid); with 

 precautions against reducing the potassium perchlorate crystals 

 to too fine a powder. After settling, the alcohol is decanted on 

 the asbestos filter and the residue similarly treated with about the 

 same amount of wash alcohol, settled, and again decanted. The 

 residual salt is then deprived of alcohol by gently heating, dis- 

 solved in 10 cubic centimeters of hot water and a little per- 

 chloric acid, when it is evaporated once more, with stirring, until 

 fumes of perchloric acid rise. It is then washed with one cubic 

 centimeter of wash alcohol, transferred to the asbestos, preferably 

 by a policeman to avoid excessive use of alcohol, and covered 

 finally with pure alcohol ; the whole wash process requiring 

 from 50 to 70 cubic centimeters of alcohol. It is then dried at 

 about 130 and weighed. 



The substitution of a gooch for the truncated pipette em- 

 ployed by Caspari will be found advantageous ; and asbestos 

 capable of forming a close, compact felt should be selected, in- 

 asmuch as the perchlorate is in part unavoidably reduced, during 

 the necessary stirring, to so fine a condition that it tends to run 

 through the filter when under pressure. A special felt of an ex- 

 cellent quality of asbestos was prepared for the determinations 

 given below and seemed to hold the finer particles of the per- 

 chlorate very satisfactorily. 



A number of determinations were made of potassium chlorid 

 unmixed with other bases or non-volatile acids and the data ob- 

 tained are recorded in the following table : 



