Document wg2XrBJ821DEaLBa9dDRd9pXD
\'OLCZfE 1 3 1956
PUBLISHERS
.M l W C A N MEDICAL ASSOCIATION CHICAGO 10, ILL.
HERVEY B EL)! S.is, Ph.D.
oi perniissii.it
itr;it:011~ t.;i be::zer.c
ana
- t C N A R D D. PA;NOTTO, E.S., Boston
vapor. The \.ai,:
r
: I . L011:11io!i\: t.3
at present is :,,i par.s per million (ppix:)
..... il parts of air ioi:;parecl lvitli 100 ppm \ \ h e n our Division \viis :irs: iounded. The \-a1332
There has been a recent interest in labeling \\-hich i r e use for naphtha 1-aporsis 1000p p n
replations for soivents and chemicals. Sev- If we tolerate ;Iconcentratioii oi loo0 p p z
,-rn] states ha1.e passed or are considering of naphtha. 2 benzene content oi belou- 2 5 %
all-jnclusive laws. The llanuiaciuring Chern- n-ill be necessary (since the molecular 1-01-
ists -Assouation has advocated warning labels umes of benzene and hesane. erc.. are simi-
011 all chemicals I\-hich can be considered lar) ; othern.ise our perniissible level ior
fir(%.iiealth, or accident hazards.
benzene 'vapor xi11 be exceeded. There is
7 1 1 Jlassacliusetts we have had a law for some question as to the sound.i:c.rs oi t h i s aplmximate1)- 20 years requiring the labeling procedure, but none the less i t is the one
oi products containing benzcne. This laiv that we will have to follow iintil tvidence is
i n s extended n-ithin the last 10 years to ai-ailable indicating a truer method oi el-ahat-
include carbon tetrachloride. In spite of the ing the 1-apor hazard in such a case.
limited coverage oi this law, its eniorcement T h e problem of the benzene conrenr oi
is not complete. and, in fact, as we shall petroleuiii solvents. particularl?- li-ith regard
sho\~*s,ome oi the problems of interpreting to the labeling reqnirenients. 11-2s recendy
even this simple iaw are estremely difiicult. brought to o u i attention by one cii ihe petro-
In the past we have from time to time leum companies. TVe decided to reel-aiuate
analyzed solvents ior their benzene content. this situation, and for this purpose a total
Frequently solvents which were obviously of eight sainples of lon--boiling petroleum
primarily petroleum naphtha have turned naphthas were obtained. These were subjected
out on careful examination to contain 1% to analysis bj- physical and chemical methods,
or 2% of benzene. Our analyses of these \\-ith special emphasis on the benzene content.
samples have upon occasion been questioned. Physical methods available included deter-
In one instance we went so far as to recover inination of hoiiing point. specific grayit?,
dinitrobenzene from the solvent after nitra- and refractive index. T h e h i l i n g point itself
tio11, recrystallize it, and carry out a mixed tells us very little about the composition
melting point determination with a known of a solvent inisture, because there are many
salnple of dinitrobenzene.
In general, our department has not made a Point of enforcing the labeling of products in \\-hich benzene \\-as presumably present as an impurity in such a concentration that tile degree of hazard produced was problemat-
-ical. During recent years, however, there have k n several downward revisions in standards
hydrocarbons with boiling 1-aiyes between
50 c and 100 C and in the vicinity oi the
boiling point of benzene, approximately SO C.
Specific gravity in conjunction n-ith the boiling point tells us considerably more. However, the reiractive index. lvhich. in general, parallels the specific graviT!.. is more conveniently determined. particularly when sinall quantities of liquid are available.
As is \\-ell hiown, the lighter iractions of
Received for publication May 4 , 1955.
petroleum consist of a \vide variety oi hydro-
lIassachusetts Division oi Occupational Hygiene. carbons. Those present in the liighest pro-
51
A . M . A-. ARCHIVES OF INDUSTRIAL
-1.52
-1.50 -1.48
-1.46
1.441.42-
-1.40
1.38 -
-1.36
REFRACTIVE INDEX
+
Ah
+A AROMATICS NAPHTHENES
+
+ +$ +
BOILING POINT O C Fig. l.-Reiractire index and boiling point of individual hydrocarboons.
having the formula LHz,.
B ~ Z E N ECON7
pints. It will be -c b e lowest R. 1.'~. fie refractive ind the increased boil
With the napt
considerably :
1.4, and the incre: hiring point is 1 the paraffins.
The aromatic b refractive index t pounds listed, an( that of toluene.
Our procedure was to fractionatc 30 in. fractionati rdradve mdev t the results agair. solvent consisting carbonswill be es! inRLasthel
-1.43
-1.42 R E F R A C T I V E
-1.40
0 SOLVENT 1802
0 SOLVENT 1803
+ PbRAFFINS
8 Cand 90 C. Fi :R~ found, in mc
B O I L I N G P O I N T 'c
Fig. Z.-Refractire indcs-boiling point curve of petrolenm naphtha solvmts.
It \vi11 be seen that the yirafins nave
the the
lowest R refiac-ve
I.*s,all below i.395, and itiaf index tends to increase with
be boiling point. -,lqth the naphthenes, refractive Indices
Iiigher I efractiye indices and that the conrent
of naphthenea was negiigible. From These
calculations benzene contents oi from 170
to 10% were found f o r the different soh ents.* I n additioii, the solvents were tested by
The aromatic benzene has a mucii higher of alkali.' In most cases seyeral fractions
cal tests were lower than those obtained
ourprocedure in analyzing these solvents by refractive index calculations. W e inter-
,mq to h c t i o n a t e 200
samples using a preted this to mean that the naphrhenic
30 in. fractionating column, determine the content of the solyents was considerable and
refractive inde.: of each fraction, and plot thus
05 Our ~ s u l n P t i o n sas to the
ti,c a,oainst the boiling points. -4 basic composirion of t h e solvents. Howeyer.
solj-pnt consisting purely of
hydro- the chemical rest did indicate concentrations
fell off sharpl!- in the fractions with boiling
c8.5 and 90 C. Finally, there =e the soivents W e were fortunate in getting a check on
''for the most part befiveen 6o and 70
-M e n the refractive indices of the fractions
*Sample calculation for fraction boiling at 81 C in Solvent 1803 (Fig-2) : R. I.'s b e n z e n ~ - 1 . 5 0 0
plotted against the mean boiling point, fraction 1.406 -corresponding paraffin 1.390.
cmres were obtained well above the area Benzene content oi iraction=
which paraffinic hydrocarbons would lie. In all cases in which the boiling point ex-
ceeded 8.5 C, a maximum refractive index
'vas found, in most cases
so. *' This
in the vicinity of
Of courser
to the
bolllnK Point of benzene, also, Imfortunately,
to the boiling point of cyclohexane. Figure
ShOMts R. I.-boiling-point CUmeS for two
'" the benzene 'Ontent Of the
solvents, assuming that the bulk Of
the naphtha consisted of paraffins of the
1.4061.390 1.500-l.390
X loo=- 0016 x100=14.5% by volume.
0.110
This calculation assumes the absence of paraffins
of low R. I.'s and of naphthenes, as indicated above.
Since this condition seldom
the
are
not precise, but they usually give some indication of
the approximate benzene content of the mixture.
Other assumptions are that the various ingredients
of the solvent form perfect mistures (i. C, no volume'
changes occur) and that azeotropic mixtures are
not produced. T h e first assumption is believed
essentially correct; the second is probably incorrect
and undoubtedly adds to the error of the deter-
mination.
A . M. ARCHIVES OF Ih'DUSTRIAL HEAL
Berizoie Cmrfexf of Naphtha SarnpIes * turer l n d made determinations with the
spectrograph for the benzene content.
Volume Benzene Per Cent
results were in good agreement with
Boning Content of
c
Sample
Range.
of Entire
chemical analyses.
KO. h a c t l o n C Fraction Sample T o t a l
In general, the benzene content
le01 -4411 A
36-11? N o t d o n e
sa3
21
.__
0.8
..- solvents ranges from 1% to 470 in
. . ~ It is not believed that the ordin
ISDG
B C D
-in
A B C D E
3 81 s94 96-111
3.8 1.5 Not done
0.4
0.2
...
... ...
1.4
such solvents would produce benz hazards. Where the benzene co
SIU 35. 65
2.5 1.6
...
0.5
esceed I%, the supplier is in violat
23
...
the Nassachusetts law if he fails to p
66- 69 1 3 1.o
..- a warning label, however.
57,74
92- 9i 1W111
4.7
1.0 Xot done
03
0..1-.
, .__
...
On the other hand, with solvents M
1.9 ing around
benzene, the possibd
Xaas spectrogram * 2.5 substantial exposure to benzene vapors
IS? 111 A B C
17s All A B C
XI- 0 57- 6s 6% 0
91
Sotdone 3.0 5.5
Sot done
50.58 ? ? ?
0.6 9 "3 0.6
._.
19
13
._.
.-.
0.05
0.4
0.03
... sulting in the iree use of the solvent in q
...
.-
32
tion must be considered. Unless the components of the solvent act to modi
effect of the benzene, use of such a s
0.6
.-_
in processes such as iabric sp-readhg,
._. might lead t o escessive =Tosure to benz
... I n the air of one plant wher
1799
D
All 1 B
C
1
6l-E5 61- 6i 67- ;1 7%79
0.0
3.1 4.6 6.0 6.4
0.00 03 a relatively low benzene content
-..
L9
1.65
31
..--
was used as a solvent in a fabric operation, a benzene 1-apor co
1 6 ... 1 ppm was found, compared IV
D 8j+aesidue 12 0.l5 4.5 concentration oi naphtha
1M9 All A B C D
61- 91 61- 70
a-E6
6- 91
95
Not done 1.7 1.4
01 Xot done
...
0.55
OS
0.02
.-.
... mined by the combustible
.._
.-.
300 ppm.
.--
SUNYARS
1.2 Nethods of analysis oi petroleum f
1600 511
63- io
1.8
...
1 8 for benzene are discussed. The re
A
GI- 66
1.9
0.7
... such analyses of eight samples of
B 66-66 2.0 C 66- 69 2.6
D Residue 4.5
0.9 Ob
Of
... ...
2.3
solvents are given. Benzene conc range irom 0.6% to nearly 7%. The
1607 -411 A
63- 70 63. 68
i.9 4 .O
...
2.0
significance of the benzene impurity
7.0
...
leum naphtha solvents is considered.
...B 66.69 i.3
2.8
...C
69- 70
10.9
1.6
-D I 1 6.6 0.35 sa
REFERENCE 1. Baernstein, H. D.: Photometric
Mass spectrosram * 6 8 tion of Benzene, Toluene, and Their N
tires, Indust. & Engin. Chm. (A
* Value supplied by manufacturer.
153251-253 (April 15) 1933.
54