548 
IOlWA ACADEMY OF SCIENCE Vol. XXIV, 1917 
Baxter and Kobayashi 7 on the other hand, have shown that 
by careful manipulation and on use of absolute alcohol at low 
temperature satisfactory results can be obtained. 
Hill s has shown that aniline perchlorate, which is easily pre- 
pared from aniline oil and perchloric acid, has a definite com- 
position and contains no water of crystallization. A known 
amount of these crystals dissolved in a measured amount of 
absolute alcohol will, according 1 to Hill, precipitate potassium 
quantitatively as perchlorate. His negative errors average 
0.0004 grams K 2 0. When, however, this is calculated into per 
cent error, it amounts to over 1.5 per cent. An explanation for 
the negative errors, according to Hill, is the incomplete conver- 
sion of KC1 into K'C10 4 . 
As the writer recently had occasion to run a large number 
of potassium determinations on the ash of forage plants and 
animal carcasses, the use of aniline perchlorate was tried under 
varying conditions. According to the writer ’s experience, the 
results are the best when the following points are observed. 
The exact strength of the alcohol used must be known, and 
none used that runs below 99.5 s per cent. For every 1.5 cc of 
water used for dissolving the mixed chlorides, 50 cc of absolute 
alcohpl should be added. A weighed amount of aniline per- 
chlorate dissolved in 50 cc of absolute alcohol must be added 
to the dissolved chlorides drop by drop with constant shaking 
and set aside for one hour before filtering. Under these condi- 
tions the writer succeeded in obtaining the following results. 
PRECIPITATION OF POTASSIUM* WITH ANILINE PERCHLORATE. 
No. of Expt. 
Wt. of KC1 
taken Gms. 
Corresponding 
Wt. taken of 
O aj 
.6 S 
W 60 
«_ TS 
o a 
. G 
Corresponding 
LWt. found of 
1 
Error in K 2 0 
Gms. 
KoO 
Gms. 
KC10 4 
Gms. 
KC1 
Gms. 
K>0 
Gms. 
1 
0.2005 
0.1267 
0.3726 
0.3670 
0.1975 
0.1247 
0.0020 
2 
0.2005 
0.1267 
0.3726 
0.3685 
0.1983 
0.1252 
0.0015 
3 . .. 
0.2000 
0.1264 
0.3716 
0.3675 
0.1978 
0.1250 
0.0014 
4 
0.2000 
0.1264 
0.3716 
0.3670 
0.1975 
0.1247 
0.0017 
5 
0.2000 
0.1264 
0.3716 
0.3677 
0.1972 
0.1250 
0.0014 
6 
0.2000 
0.1264 
0.3716 
0.3676 
0.1979 
0.1249 
0.0015 
7 
0.2000 
0.1264 
0.3716 
0.3690 
0.1986 
0.1254 
0.0010 
8 
0.2000 
0.1264 
0.3716 
0.3680 
0.1981 
0.1251 
0.0013 
9 
0.1000 
0.0632 
0.1858 
0.1844 
0.0993 
0.0627 
0.0005 
io _ ' 
0.1000 
0.0632 
0.1856 
0.1840 
0.0991 
0.0626 
0.0006 
11 
0.1000 
0.0632 
0.1856 
0.1845 
0.0994 
0.0628 
0.0004 
12 
0.1000 
0.0632 
0.1856 
0.1843 
0.0993 
0.0627 
0.0005 
♦The potassium chloride used was recrystallized from the commercial 
c. p. product. When it was estimated as chloroplatinate, it showed a purity 
of 99.9 per cent KC1. 
