V O L U M E 2 1 , NO. 1 1 , N O V E M B E R 1 9 4 9
o---
m 1401 z 41 120-
1415
-
-0
,
'"
n
loo:
W
c 8o
60-
7 rL 7 ;'
W 2ml Standard
0 E
5
40-
5a
201
tablets gave a purple color under the conditions of the test. AMPOULES. Various ingredients used as preservatives and antiseptics in the usual concentration for ampoule solutions were tested for their possible interference in the reaction. Phenol, o-cresol, the esters of p-hydroxybenzoic acid, chlorobutanol, and benzyl alcohol did not produce a color xhen subjected to the test. I t was therefore concluded that the method described can successfully be used for the assay of p-pyridylcarbinol in pharmaceutical preparations.
1 - - - - - - - - - ~ - - - - - - - _ - - - - - - - - - -
Solution IO
3
,
1
MINUTES
I
1
ADDITION OF Stability of Color
AFTER
Figure 6.
Table I.
,
LITERATURE CITED
Reproducibility of Results Tablets Deviation from mean,
Found, mg./tablct 26.3
%
26.4 26.1
Ampoules Deviation from mean,
Found, mg./tablet 51.3 51.4 51.4 50.2
26.1 26,l 25.7 26 1
52.0 51.3 51 . 9
urements, to A1 Stegermark for performing the elementary analyses, and to Morton Schmall for the preparation of the polymethine dye.
CNBr
70
0.0 +0.2 +O.2 -2.2
-1.4 0.0 +1.2
Interference of Ingredients in Pharmaceutical Preparations. TABLETS.No ingredients generally used in the manufacture of
B a n d i e r , E., a n d H a l d , J., Biochem. J . , 33, 264 (1939). E u l e r , H. von, Schlenk. F., H e i n i n k e l , H . , a n d Hogberg, B., 2. physiol. Chem., 256, 208 (1938). ( 3 ) H a r r i s , L. J., a n d R a y m o n d , IT. D., Chernistrg 6 Indiistry, 58, 652 (1939). (4) K a r r e r , P.,"Organic Cheinistr:.," p. 738, Ken. Y o l k , Elsevier Publishing Co., 1938. ( 5 ) Kodicek, E., Biochem. J., 34, 712, i 2 2 (1940). (6) Koenig, IT.,J . prakt. Chem., 69, 105 (1904). ( 7 ) S w a m i n a t h a n , SI.,I n d i a n J . Med. Sci., 26, 427 (1938). ISD. ESG. CHEM.,d x . 4 ~ . ( 8 ) W a i s m a n , H . A , , a n d Elvehjem, C. -1.. ED.,13, 221 (1941).
(1) (2)
~I
RECEIVEDJanuary .\~ERIC.AS
21, 1940.
Presented before the Analytical Group,
CHEXICAL SOCIETT, 1-orth .Jersey Section lIeeting-in-lliniature.
Januari. 10, 1949.
Source of Error in Estimating
I
Small Amounts of Parathion F. I. EDWARDS, JR. W
Bureau of Entomology and Plant Quarantine, U. S . D e p a r t m e n t of Agriculture, Beltsville, M d .
0
z
2
t
T H E course of work carried out in this laboratory on the IKanalysis for parathion (opdiethyl 0-p-nitrophenyl thiophos-
52 a
phate) residues on fruits, vegetables, and foilage by the method of Averell and Sorris ( I ) , a possible source of error was found. Examination of various graces of benzene from several manufacturers showed that there is present in all samples tested, in varying amounts, an impurity which gives a magenta color identical rvith that given bj- parathion. Inasmuch as benzene is the solvent recommended for stripping parathion residues from plant material, this solvent may constitute a common source of error. The average results obtained by analyzing 200-ml. samples of benzene by the .Iverell and Korris procedure are shown in Table I, expressed in terms of micrograms of apparent parathion.
lr I-
LL
0 W
W
2
z
W
0
E W
a
400
500
600
WAVE LENGTH IN MILLIMICRONS
700
.411 readings were taken with a Klett-Summerson photoelectric colorimeter, glass-cell model, with a filter having its transmittance peak a t 550 mp. Transmittance was set a t 100% by use of a blank containing all reagents. This ~ i ~ 1.~ Transmittancer e blank did not show any color Wave-Length Curves development.
ANALYTICAL CHEMISTRY
1416
Table I.
Apparent Parathion C o n t e n t of Benzene
Grade of Benzene
Manufacturer
C.P. thiophene-free
1-lb. bottles 5-gal. drums 1-lb. bottles Purified (99-100%), 5-gal. drums Technical, 6-gal. drums 6
This sample was turbid.
1 2
3
2
1
y ’200 m l .
-4pparent Parathion after Distillation y/lOO ml.
11.0 93.0 6 9 68.8 13. 3a
0 0 0 0 2 ‘4a
ripparent Parathion
Actual color was very faint.
Readings were taken 10 minutes after addition of the coupling agent, as in routine parathion determinations. The color, however, continued to deepen and did not become stable for several hours. Because all samples of benzene developed some color, distillation was tried to remove the impurities. The results obtained after a simple distillation, in which 10% of the benzene was discarded as forerun and tailings, are given in Table I. The impurities were not appreciably volatile on the steam bath. Further tests indicated that the impurity is probably a nitro aromatic compound, possibly nitrobenzene formed during the acid wash to remove thiophene. For these tests the sample of
benzene from manufacturer 2 was chosen, as it had shown the highest percentage of impurity. When the reduction with zinc and hydrochloric acid was omitted, about 20% of the color waa developed, an indication that the impurity was primarily a nitro compound with small amounts of an amine. Kitrobenzene, m-nitrophenol, p-nitrotoluene, arid o-nitrotoluene were accordingly tested, and in each case a magenta color was developed which to the eye &-as identical with the true parathion color. Comparative transmittance-wave-length curves were then plotted for a sample of benzene containing the impurity and for pure nitrobenzene. These data were obtained with a Beckman spectrophotometer, and are shown in Figure 1. Absorption maxima in both cases fall about 555 mp, which corresponds to the parathion maximum. Although the results set forth in this paper are not important where small quantities of benzene are involved, the analysis of spray residues requires the use of 200 ml. or more of benzene, and in such cases the error introduced may be appreciable. It would therefore seem that C.P. benzene should be distilled and wherever possible a control analysis be used as recommended ( 1 ) . LITERATURE CITED
(1) Arerell, P. R., and Norris, 51. V., A S A L .CHEZI..20,753 (1948).
RECEIVED Decemher 9, 1948.
Device for Control of Still-Head Pressures during Isothermal Distillation HAROLD SIhIMOKS BOOTH AND ROGER L. JARRY Western Reserce Unicersity, Cleveland 6, Ohio
0 DECREASE pressure surges due to interniittant applicaTtion of cooling to the still head during distillation, Booth and McKabney ( 2 ) developed the “anticipator,” a complex mechanoelectrical device, which, as its name suggests, anticipates pressure changes and thereby administers the cooling in a manner that eliminates the surge characteristic. By means of this device distillations utilizing liquid nitrogen as the still-head coolant were accomplished with very small pressure variants. McNabney (5)has outlined a proposed modification to this anticipator for use especially with dry ice-acetone still-head cooling. B s the modification had not previously been tried out, it was made in this laboratory and tested. This article describes the construction of this modified anticipator and its operation. The modified anticipator is made entirely of soda-lime soft glass. All parts are fused together, and the entire piece is mounted on a wooden plank, after which it is fused to the stillhead line of the distillation apparatus. Tube A is made of 7-mm glass tubing, B and D of 20 mm. tubing, and C of 5-mm. tubing. Stopcock E, used as a throttling valve, is a 2-mm. bore capillary stopcock. Reservoir F is connected below D by means of an ordinary stopcock. Length J is just over 760 mm., while length T is slightly greater, so that the bottom of D is a t least 760 mm. from the center of B. *4t H a platinum wire is sealed in and the electrical contact between it and the adjustable probe, G , made of 26-gage nickel wire, is made through a 6-volt relay, to energize a small pump which supplies the coolant to the still head. In operation, the mercury is set by means of the leveling bulb F , so that the desired pressure head will result, the level in B being near the center. As shown in Figure 1, the mercury level in the three columns is set for atmospheric pressure distillation; for distillation a t pressures less than atmospheric the level in the three columns has to he adjusted so that when a vacuum is attained, the level in A will he in the middle of B and the difference in height between that level and those in C and D gives the pressure a t which distillation is to be carried out. As the still-head pressure increases the mercury will he forced down in A and up in C and D,contact will he made with the adjustable probe, and the still-head cooling agent will be injected into the still head. As the still head cools, the mercury will rise in A , owing to dropping pres-
sure, and fall in C and D,thereby breaking the 6-volt circuit and stopping the cooling pump. At this equilibrium point, D which has fallen less rapidly than C, forces the mercury in that column up and thereby starts it slightly in advance of the building pressure in A . By this means future contacts will be in advance of the full pressure-Le., anticipate full pressure. In a similar manner D,rising more slowly than C, xi11 tend to deplete that column and make it fall sooner, anticipating the pressure drop. The rate a t which the mercury flows into D ill necessarily control the sensi-
QWILlY
Figure 1. Modified Anticipator
