Use of a Monochromator in Refractometry Refractive Indices and Dispersions of High Molecular Weight Hydrocarbons RAYMOND T. DAVIS, JR.~, and ROBERT W. SCHIESSLER2 Whitmore Laboratory, College o f Chemistry and Physics, The Pennsylvania State University, University Park, Pa.
spectral lines and comparing these values n-ith tabular values. The dispersion characteristics mere also checked and compared with the values provided by the manufacturer. The diapersion characteristics are plotted in Figure 2. The accuracy of the refiactometer was checked first a it11 the glass test piece provided with the instrument. I t was checked against one or more of the S B S standard refractive indes liquids, toluene, methylcyclohexane, and 2, 2,4-trimethylpentane, at each of the seven Tyave lengths and a t the given temperature. Hydrocarbons. 911 of the hydrocarbons studied were prepared a t The Pennsylvania State University under the direction of one
A monochromator with a tungsten filament lamp may be used as a source of monochromatic light suitable for refractive index and dispersion measurement. The index of refraction of 14 hydrocarbons of high molecular weight is reported at 25" and 30" C. at a series of seven wave lengths.
T
HE usual procedure for measuring irides of refraction a t different wave lengths is to use standard lamps, together with suitable filters, to obtain monochromatic light (8). The Bausch & Lomh Precision Abbe-type refractometer is calibrated by the manufacturer for measurements at the following xave lengths: Wave Length,
Usual Spectral Source Helium red Hydrogen C Sodium D I , D? Mercury e Helium blue Hydrogen F 3Iercury y
4.
GG78.1 6562.8 5892.6 5460,7
5015.7 4881.3 4368.3
MONOCHROMATOR
Commercially available sodium vapor and mercury vapor lamps are satisfactory sources: They give intense light, are stnble, and are easy to operate. On the other hand, the hydrogen and helium sources are clumsy in operation and the former is difficult to maintain in constant operating form. This paper reports the use of a monochromator coupled with a high intensity tungsten filament lamp as a source of radiation of narrow wavelength spread. It is an especially suitable replacement for the troublesome helium and hydrogen lamps, and may be used for any wave length in the visible region with ease. The index of refraction of 14 hydrocarbons of high molecular weight (American Petroleum Institute Research Project 42) is reported a t the above wave lengths a t 25" and 30' C.
W A V E L EN GTH DIAL
LIGHT
EXPERIMENTAL
Instruments. A Bausch & Lomb Precision, Abbe-type refractometer was used, covering the range n = 1.323 to 1.657 and calibrated at seven nave lengths. The sodium vapor lamp which is normally an integral part of the instrument was removed and mounted on a separate stand. .4 Gaertner high dispersion wave length spectrometer, Model No. L231, was used as a monochromator. The eyepiece of the instrument was replaced by a calibrated bilateral slit. The instrument disperses light from 800 to 400 mp. The instrument dial was graduated in units of 1 mp and could be estimated to 0.1 r n M (1 A). The light sources used for calibration and measurements consisted of the sodium vapor lamp provided with the refractometer, a Bausch & Lomb Model H4 mercury vapor lamp, and a Bausch & Lomb microscope illuminator (KO. 31-33-78) with an aspheric condenser and 6-volt tungsten ribbon filament lamp. These lamps were mounted on a single stand in such a manner that any lamp could be rotated into place without dismounting any other lamp. The temperature of the refractometer prisms was maintained constant and controlled to k0.02O C. by the use of a constant temperature bath (Precision Scientific Co., Nog 6600). The refractometer thermometer, graduated in 0.2 divisions, was checked against a Sational Bureau 3f Standards certified thermometer. The arrangement of the instruments is shown in Figure 1.
Figure 1.
.hrangement of instruments
Calibrations. The accuracy of the monochromator dial was checked by reading the wave lengths of the sodium and mercury 1 Present address, U. S. Steel Research and De\elooment Laboratory, Pittsburgh, Pa. 2 Present address, Socony Mobil Laboratories, Paulsboro, N. J.
WAVELENGTH
Figure 2.
1824
(ai
IN
MILLIMICRONS
Dispersion characteristics
V O L U M E 2 7 , NO. 11, N O V E M B E R 1 9 5 5
1825
Table I. PSU
KO. 8
Empirical Formula CsiHsl
Compounds Studied Name
Structure
clo-c-cl0
1 1-n-Decylheneicosane
(Lo
1-Phenyl-3 (2-phenylethyl) hendecane
19
C2:Hu
1-C yclohexyl-3 (2-cyclohexylethyl) hendecane
[Q-C2-1
- 2
c-cs
[(>-c2-] ___
9-n-Octylheptadecane
Cs-C-cs
9 (3-C~clopentylpropyl)heptadecane
c*-e-cs
c-C8
h 8
111
C2sH13
l-Cyclopentyl-4(3-cyclopentylpropyl) dodecane
A
c-cs 2
113
CZIHU
1.7-Dicyclopentyl-4(2-cyclohexyleth~l) heptane
122
CiiHsa
1,l-Di(a1pha-Decalyl)hendecane
134
C38Hia
13-n-Dodecylhexacosane
[~>c3-l
~c-c~s>
[$3];"" c.2-c-cII ~
c 1 2
500
C19Hio
i-n-Hexyltridecane
cs-e-cs I
c 6
503
CisHx
1,l-Diphenylheptane [Q-],c-C.
516
Cl&Hir
1,l-Diphenylethane
549
C ~ H K
4-n-Propjiheptane
[---p-c CsC-Ca
I
C3
567
CiiHio
I-Methylnaphthalene
05 'W
of the authors (6, 61,except PSU 567, which was supplied by C. E. Boord and I. ammonium salts nrr d l titrated under these conditions, provided that the salt is not :t halide. The use of the more dilute titrant increases the precision of the determinations. The end poirit is detected potentiometrically through the use of a glass-c:iloniel electrode com1jin:tt ion. Sodium methylate, the uswil titrant for the acid portio~iof amine salts, cannot be used to determine the amine salts i n the polymers, as this reagent attacks the acrylonitrilr portion of the S o definite end poiiit c i ~ n polymer, apparently by hydrol) lie obtained in such a titration. 1,8-Di-o-tolylguanidine, designated 117 Davis and Hetzei, ( 1 ) :is one of the stronger substituted guanidine lmsc+. \vas found c:ipaI~le of titrating heterocyclic amine salts in the presence of the fi,ee srnine, but could not be used successfully with aliphatic amine salts. This is undonbted1)- due to the nearly equal basic strength of t,he amines and the titrant. Thip h s e combines with the acid portion of the salt and is, therefore. useful in determining that part of the compound. I t does riot attack the nitrile portion of the polymer. TITRATION OF QUATERN.4RY A\IMONIURI SALTS
All of the polymers containing quitternary compounds were prepared by the copolymerization of acrylonitrile and a quaternary ammonium chloride in the presence of mineral acids. The chloride ion is not completelj, displaced, so that some of this anion remains in the polymer. The presence of the halide ion necessit,ates the use of Pifer and Wollish's ( 6 )mercuric acetitte modification. Their work was done by dissolving an amine or quaternary ammonium halide in glacial acetic acid and adding R solution of mercuric acetate. The formation of the mercuric halide removes the halide ion froin solution and the excess mercuric acetate, being essentially iinclissociated, does not intwfrre i\-ith the perchloric acid titration.
