198 Proceedings of Indiana Academy of Science 
sary with this procedure include the sample, the mixed halides, and the 
remaining silver chloride, one less than with the other procedure. 
The modified method is essentially similar to that employed by 
Treadwell’ who filters the mixed halides into a weighed Fresenius as- 
bestos filter tube of difficulty fusible glass. The tube and contents are 
weighed, the halides chlorinated in it, and the tube again weighed. 
The results shown in the accompanying table illustrate typical 
determinations as made using the two schemes of chlorination. 
Chlorination in Boat Chlorination in Crucible 
Sample 
Number FCI %Br %Cl %Br 
1 35.30 27.80 35.58 27.51 
35.29 27.81 35.44 27.57 
35.27 27.56 35.53 27.45 
35.13 27.92 35.42 27.60 
2 38.10 24.90 37.90 ’ 25.10 
37.82 25.18 38.07 24.80 
37.74 25.14 38.17 24.76 
38.03 25.01 38.10 24.74 
et Oe eh Penance catetie an nits 38.10 24.78 
dete ec ciile eerie Tiny | eeltig ake. s ele a cite aah a. ore 37.96 25.20 
%Cl %I %Cl I 
3 45.63 18.75 45.59 18.91 
45.50 19.07 45.44 18.79 
45.62 18.97 45.50 18.88 
45.70 W890 Nace cee winie cia ic dvetevete vena erp [lately ote a Rete armen an ae eee 
4 50.41 12.46 50.20 12.92 
50.33 12.55 50.35 12.72 
50.30 12.63 50.26 12.60 
5 2.95 9.71 53.15 9.35 
05 9.70 53.17 9.45 
53.08 9.50 53.10 9.50 
52.99 A i ch Armed Ec 
if 0 Br - ol Br %I 
6 17.01 19.78 17.02 19.74 
16.91 19.36 16.97 19.68 
eh, Rete nn aches ses se |e Sis ts poe ois slelivemsi nto 17.19 19.39 
The analyses for sample No. 1 were made by the junior author. 
The other results have been taken from the reports submitted during 
1919 and 1920 by the students in general quantitative chemical analysis. 
While these analyses do not check as well as might be desired, most 
indirect, gravimetric methods are subject to rather large errors unless 
approximately equal amounts of the two constituents are present and 
the multiplying factors used for the calculation is small. Ashley’ cites 
an example where an error of 1 mg in a weighing results in a per- 
centage error of 26.20 for one of the constituents. 
CONCLUSION. 
A modification of the method for chlorinating mixed silver halides 
has been proposed. Its advantage over the method previously employed 
1 Treadwell-Hall—Analytical Chemistry, Vol. II, p. 334 (1915). 
2 Chemical Calculations, p. 190 (1913). 
