40 Gooch and Kreider — Detection of Alkaline, etc. 



the strongest hydrochloric acid and evaporation to dryness. 

 Nitric acid does not yield so readily to the decomposing action 

 of hydrochloric acid and may be detected in the residue after 

 four similar treatments. To destroy nitrates, therefore, we 

 followed the general plan of decomposition employed in a 

 quantitative method for the determination of nitrates previ- 

 ously elaborated in this laboratory* and treated the dry sub- 

 stance to be tested with 2 cm 3 of a saturated solution of man- 

 ganous chloride in the strongest hydrochloric acid. The 

 liquid was evaporated to dryness, and the residue was again 

 treated similarly with one or two cubic centimeters of strong 

 hydrochloric acid. This method of decomposing the nitrate is 

 peculiarly advantageous since the decomposing agent is itself 

 an excellent indicator of the completeness of the work of re- 

 moval. Two or three treatments serve to remove the nitrate 

 entirely ; but before proceeding with the test it is necessary to 

 remove the manganese which has been introduced, inasmuch 

 as manganese chloride will of itself evolve chlorine, by ex- 

 change for oxygen, when heated in air. Sodium carbonate in 

 solution answers the purpose of removing the manganese 

 (together with other interfering substances) and the filtrate 

 from the precipitated manganous carbonate leaves on evapora- 

 tion a residue, which, when treated with the anhydrous zinc 

 chloride, gives indications for the perchlorate if it is present 

 in appreciable amount. The results of a series of tests for 

 potassium perchlorate associated with the chlorate and nitrate 

 of the same element and recorded in the following table.. 







Table 



II. 



Treatment for the 



Indication of 



HO4 taken. 



KC10 3 taken. 



KN"0 3 taken. 



removal of chlo- 



the 



grm. 



grm. 



grm. 



rate and nitrate. 



perchlorate. 



0-0005 











By HC1 



Strong. 



0-0003 











a 



u 



0-0002 











a. 



Good. 



o-oooi 











a 



a 



o-oooi 











a 



Trace. 



0-0005 



o-i 



o-i 



By HCl + MnCl 2 



Strong. 



0-0003 



o-i 



o-i 



ct u 



Good. 



0-0003 



o-i 



o-i 



a u 



Good. 



0-0002 



o-i 



o-i 



a a 



Trace. 



o-oooi 



o-i 



o-i 



u a 



Trace. 



o-oooo 



o-i 



o-i 



a a 



None. 



It is plain that O0001 grm. of potassium perchlorate may be 

 found with certainty when associated with - l grm. of the 

 nitrate or chlorate or both. 



* Gooch and Gruener, this Journal, xliv, 117. 



