: 
Kreider— Quantitatiwe Determination of Perchlorates. 297 
Taste VII. 
KCl0, taken. KI taken. HCl taken. KCIO, found. Error. 
germs. orms. em? erms. gris. 
(32) 0°1000 a 3° 0°1003 0°0003+- 
(33) 0°1000 3° 3° 0°1006 0°0006+- 
(34) 0°1000 3° 3° 0°0998 0°0002 — 
(35) 0°1000 4° 4° 0°1003 0°0003-++ 
(36) 0°1000 3° 3° 0°1003 0°0003+ 
(37) 0°1000 o” 4° 0°0999 0:0001 — 
(38) 0°1000 3° oS 0°1008 0°0003-+- 
(39) 0°1000 a 4° 0°1001 0°0001+4 
(40) 0°1500 3° 4: 071493 0:0007 — 
(41) 0°2000 6° 6° 0°1999 0°0001— 
(42) 0°2000 6° 6° 0°2009 0°0009 + 
(43) 0:0100 3° 3° 0°0099 0-0001— 
(44) 0°0100 3° 3° 0°0100 0°0000 
(45) 0:0000 2° 3° 0°00038 0°0003+- 
In experiments (40) and (48) during a momentary pause in 
the shaking of the bulb during the absorption, a black deposit 
of iodine began to form on the glass, and the result proves the 
importance of the precaution previously given, that the hydri- 
odie acid should be kept hurling about the bulb until the 
action is completed. The blank determination (45) shows a 
constant error of the process which is about 0°0003+ and will 
be seen to correspond very closely to the average error of the 
determination. The cause is doubtless to be attributed to the 
trace of air which may remain in the bulb or be dissolved in 
the water. Since it can easily be determined and the correc- 
tion made, it does not detract in any degree from the reliability 
of the determination. 
To determine perchloric acid associated with other oxidizing 
agents it is only necessary to treat the mixture with the reagents 
which this investigation and the one referred to has shown to 
accomplish the reduction without affecting the perchlorate ; 
subsequently evaporating to dryness and treating the residue 
according to the above process, viz., by heating in a current of 
carbon dioxide until decomposition is complete; collecting the 
oxygen over caustic potash; allowing it to enter a partial 
vacuum bulb containing a solution of potassium iodide, hydro- 
chloric acid and nitric oxide under constant agitation; and 
determining by means of a standard solution of arsenic the 
amount of iodine set free. The method is proving applicable 
also to the determination of oxygen in air or wherever it may 
be obtained in the free state, unless diluted to such an extent 
with other gases that the vacuum would be filled by the dilu- 
ent; even this contingency could be met by enlargement of 
the absorption bulb. 
Many helpful suggestions are to be credited to Professor 
Gooch. 
