acid, 40 mi. of water), transfer to filter tube, and fill tube with water. After a few minutes draw solution through the mat and rinse the flask and tube with several small portions of water, combining washings with the solution. Add a few drops of 5% phenol to decolorize the solution and determine selenite by measuring the color produced by reaction with diaminobenzidine according to the method of C k n g . This procedure will convert selenium in biological materials into selenite and appears to be quantitative \vithin 7. It is, of course, necessary t o be reasona-
bly careful and to determine a reagent blank. I n the Cheng procedure, the use of more concentrated formic acid, thereby reducing the volume, gives more consistent results. In any case, the volume must be kept constant. Diaminobenzidine, synthesized b y the method of Hoste (Z), gives us more consistent results than the commercial material we purchased.
(2) Hoste, J., Anal. Chim. Acta 2, 402 (1948). (3) Hoste, J., Gillis, J., Ibid., 12, 158 (1955). ( 4 ) Olson, 0.E., personal communication, 1952.
LiTERATURE CITED
WORKmade possible by a grant made by the Tektronix Foundation, Portland, Ore., to the Chemistry Department of the University of Portland.
(1) Cheng, K., ANAL. CHEW 28, 1738 (1956).
O s 2
CARLW. BOKHORST JAhlES J. hfATTICE University of Portland Portland 3, Ore.
~~
Determination of Clo-Akylbenzenes
Determination of Isomeric Dimethyl Benzyl Alcohols
D. E. NICHOLSON and S. H. HASTINGS, Humble Oil 8, Reflning Co., Baytown, lex. CS- 105
D. E. NICHOLSON, Humble Oil & Refining Co., Baytown, l e x . Slit
I
No.
Slit Accuracy
Componenf I Range Name 1 Formulo 1 %
%
B.L.
AX or
Concn. glliter Length
Pts.
Av
mm
X or
(mm)
Y
Range
1
3,5-Dimethyl benzyl alcohol
CgH120
% % ~0-100 10.5 1 1 . 8 5 ~
2,4-Dimethyl benzyl alcohol
CgH120
0-100 f 0 . 5
2,5-Dimethyl benzyl alcohol
C~HIZO
-
3
Relotive Absorbancer-Analyficol ComponentlX
0.713 0.394
0.050 0.242 Material Purity:
P o i n t X
Calculofion:
Successive a p p r o x A
22.21~
18.49~
3
1,4-Dimethylbenzene
Base line-
Inverse m a t r i r G r a p h i c a l
Mafrix: 12.35~
0.020 0.202 0.048
0.017
0.345 0.882 0.252
0.202
3
0.998
Successive a p p r o x L
12.20p
0.690 0.109 0.219
0.088
P o i n t X
0.211 0.015 0.017
2 Material Purify:
0.139 0.294
Minimum of 99%
Instrumenf: Perkin-Elmer Model 11 2, NaCl prism Sample Phase: Solution in carbon disulfide
CS- 107
Range
-
Cell Windows: NaCl Absorbance Measurement:
Concn. gllifer Lengfh
Calculation:
mm
-
1 1 2 . 3 5 ~ 0.229 0 . 0 4 4 ~ 0.027
99.9%
Componenf
1,3-Dimethylbenzene
1 G.218 0 . 0 4 2 ~ 0.027
11.85p
0.068
Humble Oil & Reflnlng Co., Baytown, l e x .
2
1 0.202 0 . 0 3 9 ~ 0.027
1
0.110
S. H. HASTINGS and D. E. NICHOLSON
phenone
mm
Component/k
0.180
Determinatioir of 1r3- and 1 ,CDirnethylbenzenes Containing Benzophenone
-
0-100 k 0 . 5
Relative Absorbancet-Analyfical 21.32~
AA or Av
Concn. g/lifer Lengfh
~-
Cell Windows: NaCl Absorbance Measuremenf:
Mafrix:
20.16~
12.20p
(mm)
Instrument: Perkin-Elmer Model 112, NaCl prism Sample Phase: Solution in carbon disulfide
Insfrumenf: Perkin-Elmer Model 11 2, CsBr prism Sample Phose: Solution in carbon tetrachloride
Inverse m a t r i x Graphical-
or v 6.1. Pfs.
Formulo
-
Calculation:
X
Name
2
Base line-
Accuracy
No.
-
Cell Windows: CsBr Absorbonce Measurement:
CS-106
-I
f0.5 CsHlo
0-100
f0.5
i x K o-100 rto.5
5.95p
1 0.200 1 0 . 0 3 5 ~ 1 .oo
I
1 3 . 0 2 ~ 0.690 0.061~
1 1.00 1 1 .oo
Base line-
Inverse matrixGraphical-
P o i n t X Successive a p p r 0 x . X
Relofive AbsorbancerAnalyfical Matrix: ComponentlX
5.95p
13.02~
12.59~
1 2
0.219
0.007
0.002
0.000 0.000
0.272 0.002
0.002 0.277
3 Maferial Purity:
1.3- and 1,4-dimethylbenzenes, 99.5%; 98%
benzophenone,
VOL 31, NO. 12, DECEMBER 1959
2107
