l
-12 0
~
1
'
1
'
/
'
1
~
1
'
l
'
/
'
-l
'
-
I
-I0 0
no.
-
r'
-6.0
-
0
20
4.0
6.0
8.0
I00
CONCENTR&Tl3h
OF
I20
140
I60
I80 200 100 %
the 2,~-dichloro-G-nitroaiiiliiieindicator which has been reported by Kilpatrick and Hyiiian3 arid reconfirmed in this study. The values of II,, the function for some sulfuric-trifluoroacetic acid mixtures suggested by Killxitrick m d Hyman using hexaniethylbeiizenc as ai1 indicator, are also in poor agreement with the values shown in Fig. 1. Similar lack of agreeiiierit between indicators has been noted by other workers, especially, nates and Sch\varzeiib:Lch,aand Paul arid Long7 have discussed this to sonic extent. In the case of the hexametli!-lbenzciie, i t is perhaps not unreasonable to observe that the rearrangenient needed in order to place a proton 011 the organic molecule makes this reaction soxiiewliat differeiit from the addition o f a proton to the iiitrogen in an amine grouJ). Great care must he exercised in extrapolating pure proton transfer ineasurenieiits gi\-en by IIo values i s ) I
\crptihri sigiial oii :i iccortiiiig potentiometer. Tlie spcctr.i 1vi:i-e c:ilil!rntetl witii rcspcct t o field strength by 1 5 of :i protoii rcborinrice spectrometer a n c l a 1,000 . cr~.st,il ( ~ ~ i ! l a t ~\\lienever r. tlie protoii resoii:incc fr(.qri.~ricy i J i C c I I I l e equal t o a n harmonic of the crystal osciILitpr, n pi;) ~ v : , splaccti on t h e recorder trnce. This proceiliirc rc,i:ltc ri i i i fielil rnat-h-crs at 235-gauss iiitvrvals i' nctiiai ficlil strengths to which Y: -,\t:re ,lcterniiiieil h y calibrating
Preparation of the Samples.-Tlie
ndiorberit ni;iterials
\vcrc (Iiietl :it 110' for 4 h r . , ntitl :ipproxilri:itely ?,-gr&ln w i r i p l e s ivc.i.e \\c.iglictt :iccurat~ly into sepnriite flasks. \'~iri,iixskiic~;~;iiq!T:iiltitics oi sr:i~itl:irtlizeti t c u t h molar SOILItiolir of tiic i):iraiii:;gnetic mIts xvcrc attricd, aiitl tile flasks M Lrc stf,1jpcrcil. 'rile soliitiuns Jvcre :illowed t o equilibrate
w i t h tlie ~.rlsc,rbrrits:it zli,ikiiigs of thc fl\i\ks.
cmpcrature with occasional .orbentmns theii rctnovetl on ,i pti1icr filter :iiirI ;\-aslie 11 times with distilled water. 'rile ti1tr;itc :in11 $1
