300 Gooch and Mar — Determination of Chlorine. 



hot steam in order to avoid the inconvenience of condensing 

 the distillate and testing it for iodine. We found that red 

 litmus, preferably wet, is a most sensitive agent for the detec- 

 tion of iodine under the circumstances, taking on with expo- 

 sure to traces of the vapor carrying that element, a distinct 

 gray blue, deepening with exposure to larger amounts into a 

 lavender blue. The addition of 0*005 grm. of iodine to 

 400 cm 3 of boiling water produces immediately upon red 

 litmus paper the characteristic lavender blue color, and the 

 test grows fainter and fainter as fresh test-papers are exposed y 

 until at the end of live minutes, or thereabouts, when the 

 litmus paper shows no color, the cooled solution yields no 

 iodine to nitrous acid and chloroform. This reaction of 

 litmus we found of great value and in no case in which an 

 exposure of two minutes' duration failed to develop the char- 

 acteristic color were we able to find iodine in the cooled liquid. 

 To prevent mechanical loss of liquid we made use of the trap 

 described in a previous paper from this laboratory, consisting 

 simply of an ordinary two-bulb straight drying tube cut off 

 short and hung with the large end downward in the mouth of 

 the Erlenmeyer flask. The residue in the flask after the 

 expulsion of the iodine was treated with silver nitrate, and the 

 precipitated chloride was determined similarly to that obtained 

 in standardizing the solution of potassium chloride. 



Several determinations in blank — that is, experiments from 

 which the iodine was purposely omitted- — are included, for the 

 sake of comparison, in the tabular statement. 



Series I. 



H 2 S0 4 

 [1 : 1]. 



cm 3 . 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 



Fe 2 (S0 4 ) 3 . 



HN0 3 . 



grm. 



cm 3 . 



2* 





2* 





2* 





2* 



2 



2* 



3 



2* 



3 



at 



3 



.2f 



5 



2t 



5 



2f 



5 



2f 



6 



KC1=HC1. 



grm. 

 0-4960 

 0*4970 

 0-4942 

 04969 

 04956 

 0-4969 

 0-4949 

 0-4970 

 0-4955 

 0-4967 

 0-4964 



grm. 

 0-2425 

 0-2429 

 0*2416 

 0-2429 

 0-2423 

 02429 

 0-2419 

 0-2429 

 02422 

 02428 

 0-2427 



KI. 



Initial 

 volume. 



B 

 



on 



+=> 



AgCl = 

 found. 



= ELC1. 

 found. 



grm. 



cm 3 . 

 400 



cm 3 . 

 300 



40 



grm. 

 0-9536 



grm. 

 0-2425 





400 



300 



40 



0-9534 



0-2624 





400 



300 



30 



0-9509 



0-2418 



-- 



400 



300 



30 



0-9559 



0-2431 



1 



400 



350 



30 



09546 



0-2428 



1 



400 



350 



23 



0-9662 



0-2432 



1 



400 



300 



27 



0-9523 



0-2422 



1 



400 



250 



55 



0-9559 



0-2431 



1 



400 



300 



30 



0-9524 



0-2422- 



1 



400 



300 



33 



0-9546 



0-i'428 



1 



400 



300 



30 



0-9550 



0-24291 



Error. 



grm. 

 0-0000 

 00005 — 

 0-0002 + 

 00002 + 

 0-0005 + 

 0-0003 + 

 0-0003 + 

 0-0002 + 

 -0-0000 

 0-0000 

 0-0002 + 



These eminently satisfactory results prove the trustworthi- 

 ness of the method. 



* The iron was added in the form of iron alum, 

 f The iron was added as FeS0 4 oxidized by BN0 3 . 



