V O L U M E 2 4 , NO. 9, S E P T E M B E R 1 9 5 2 Table I.
1509
Effect of Kerosene Content on the Alcohol Required for Dissolution
Tziiip..
C.
20
Alcohol used, 93.4% by volume a t 15.5' C. Gasoline used, British pool spirit Alcohol Required for Kerosene Gasoline hIiscibility Point, 111. 70 by volume Si1 100 19.5 80 20 i "3' O7 . 5 50 50 12.0 21.5 142.0
12
Table 11. Effect of Strength of Alcohol Used on Data Shown in Table I
Iiil 20 50
Alcohol used, 9.7.3L;: by volume a t 13.3° C. Gasoline used, British pool spirit Alcohol Reqiiired for BIiscibility Point, AII.
TEinp..
C.
20
100 80 50
12
Table 111. The temperature effect has been investigated over the range 12' to 20" C., and the follon-ing facts emerge (Table 111). For niistures containing up t o 2OY0kerosene, a temperature difference lietween standardization and determination. of 1 C., will amount to only about 0.25% on the apparent kerosene content (1.25% error). For mixtures richer in kerosene, this variable becomes inereasingly critical, until a t 50% kerosene a departure from the standardization temperature of 1 " C. is equivalent t o an error of 0.75% on the apparent kerosene content (1.50% error). If the laboratory temperature is fairly constant, this temperature effect can he ignored, but if great precision is required, this
50
Gasoline
14.5 23.5 46.5
h-il 20
100 80 50
[E 54.5
Xi1 20 50
100 80
% by volume
50
50
Temperature Effect Expressed as a filean Coefficient, from 12" to 20" C.
Kerosene in Mixture, Yo h'll 20
Kerosene
93.4% Alcohol, 111. per 1' Rise 0.125 0 . 2.50 0.56:3
92.3% Alcoho1,'MI. per 1' Rise 0.188 0.313 1.000
variable may be eliminated by standardizing the alcohol inimediately before the set of determinations. The relevant results are set out in Tables I to 111. R E C E I V Efor D review October 24, 1951.
Accepted June 5 , 1952.
Equilibrium Constants in the Interaction of Carbonyl Compounds with Hydroxylamine NATII.AN SHAROS, Tlie .4gricuZturaZResearch Station AND
AH.IROS KATCHALSKY, The W'eitrnann Institute of Science, Rehocot, Israel
HE decrease in p H accompanying the rezction of amino acids rand of aldehydes is used extensively for the analytical determination of amino acids and peptides. Levy ( 2 ) evaluated, from the p I I depression, the equllibrlum constants of the formol interaction. Equilibrium constants of the interaction of aldoses with amino acids and peptides &-ere determined in a similar manner b y Ilatchalsky (1). Recently, Roe and 3IitcheIl (3) proposed the use of the p H drop, folloii-ing the mixing of hydroxylamine hydrochloride n ith carbonyl compounds, as a rapid means for the quantitative analysis of aldehydes and ketones. The data given by Roe and hfitchell comply satisfactorily 'i\ ith the theory proposed for the interaction of aldose- and amino acids and may be used for the evaluation of suitable equilibrium constants. The proposed mechanism of the interaction is: K
HOSHs+ &H O S H L +A
30
20 I
n Q
cn
.0
&
c
10
+H+ 0
where A is the carbonyl compound.
10 20 Conc. of butyraldehyde x103
D
Figure 1. Determination of Equilibrium Constant L f o r Interaction of Butyraldehyde and Hydroxylamine
Hydrochloride In aqueous solution, Equation 12
Let us denote the total concentration of the carbonyl compound by 0 and the total concentration of hydroxylamine by CB. Denoting the initial concentrations by a subscript o we get
+ A:KOH + (+",OH), SHzOH + 'Tu"30H + A:NOH
CA = A, = A CB = (",OH),
(3)
=
(4) hIaking use of Equation 3 and the equilibrium Equation 2 we find
A :SOH =
L.CA.KH,OH 1 L.
+ h"m
The concentration of S H L O Hat the pII a t the end of the euperiment (about pH 2.5) is sufficiently small to make L.SHLOH< 1. Therefore, A : S O H = L.CA.SH,OII
ANALYTICAL CHEMISTRY
1510 which introduced into Equation 4 gives
CB = ",OH
(1
+ L.CA) + -hTHZOH
=
(KH,OH),
+ ( 'NHzOH),
(6)
During the experiments the concentration of the chloride ions is constant; hence electroneutrality requires
H, + (+SHsOH),
=
H
+ +NHsOH
(7) Jvhere H, and H denote ion concentration a t the beginning and a t the end of the interaction. T h e experimental conditions are such that the hydroxylamine concentration is sufficiently high t o make t h e hydrogen ion concentration negligible in comparison with t h e concentration of t h e hydroxylamine +NHaOH (+SHaOH), Introducing 8 into 6 leads to t h e result (NH,OH), = ",OH
(1
+ L.Ch)
(8) (9)
Now t h e ratio of the initial and final hydrogen ion concentrations is from Equation 1: H +XH,OH - -- (",OH), XHo (+SH,OH), IVH20H
(10)
which gives after making use of Equations 8 and 9, t h e final equation
H
g = 1 + L.CA ApH
=
log (1
L = 1250
lit. mole ~
.Ipplying Equation 12 to the series of other carbonyl compounds given in the following table (3) we find the following equilibrium constants: h p H At Equilibrium Compound Equilibrium Constant, L Acetaldehyde 1.17 1150 Vanillin 1.17 1150 Acetone 1.17 1150 Diethyl ketone 1.10 970
411 ApH values are for solutions of 0.012 millimole per nil. of carbonyl compound. The result of these calculations proves that once the equilibrium constant is determined with sufficient precision the concentration of the carbonyl compound is directly obtainable from the p H decrease according t o Equation 12. LITERATL'RE CITED
or, taking negative logarithms pH, - p H
data given by Roe and Mitchell ( S ) , Figure 1, for the reaction of butyraldehyde Kith hydroxylamine. Figure 1 represents the plot of the antilogarithm of ApH versus the butyraldehyde concentration. The points lie on a fairly straight line correspondiiig to an equilibrium constant.
+ L.C!)
(12)
This simple equation may be amply verified on the basis of the
(1) Katchalsky, A., Biochem. J . , 35, 1024 (1941). (2) Levy, bl., J . Biol. Chem., 99,767 (1933). (3) Roe, H. R., and Mitchell, J., Jr., ANAL.CHEM.,23, 1758 (1951).
RECEIVED for review April 15, 1952. Accepted June 2 , 1952
Modification of Norman-Jenkins Method for Determination of Cellulose EM-METT BENNETT Massachusetts Agricultural Experiment Station, Amherst, Mass.
orman-Jenkins method (3) for the determination of Tzu;se has been widely accepted. One of the highly desirable features of this method is the Maul6 reaction nhich makes the end point of the procedure definite. Intermediate steps, however, are time-consuming and subject t o error. Maynard and coworkers ($2) have proposed a revised method which they find will yield results quantitatively comparable to those obtained by the Norman-Jenkins method. The present revision is novel in that preliminary treatments are made with sodium chlorite instead of alternate treatments with alkaline hypochlorite and sodium sulfite; all separations except the final one may be made in the original container by means of the centrifuge and a microfilter stick.
cotton weighing 0.02 gram supported by a glass bead. These are held in place by a piece of batiste stretched tightly over the top and tied around the lip of the bulb ( 1 ) . Thirty-five milliliters of 6 % sodium sulfite and 20 ml. of water were added to the tube, which was placed in a bath of boiling Tvvater for 10 minutes, then centrifuged. Forty milliliters of cold water, 2 nil. of 20% sulfuric acid, and 5 ml. of sodium hypochlorite (Chloro\) containing approximately 5.6% of chlorine were added t o the residue. The reaction was allolTed to proceed for 10 minutes away from direct sunlight, then centrifuged. This time, 30 nil. of 67, sodium sulfite and 20 ml. of \%ater%ere added and the procedure was continued as before. The cycle mas repeated until the Maul6 reaction was negative. The pulp was treated with hot water t o remove salts, centrifuged, and finally transferred to a suitable Gooch crucible and dried a t 105" C. The cellulose was determined by the loss in weight of the pulp on ignition.
PROCEDL-RE
One-gram samples in triplicate of air-dried plant material of 25- to 50-mesh were weighed into 150-ml. beakers or 100-ml. centrifuge tubes. The following were added t o each container: 3 ml. of a solution of sodium acetate of p H 4.5 prepared by adjusting a 20% solution of acetic acid t o p H 4.5 with sodium hydroxide; 5 ml. of a 10% aqueous solution of sodium chlorite; and 40 ml. of water. T h e contents of the beaker were stirred, covered with a watch glass, and placed under a hood on a steam bath, the temperature of which was about 80" C. ( 4 ) . Thirty minutes later another 5-ml. aliquot of rhlorite was added and the reaction allowed t o proceed for another 0.5 hour with occasional stirring. If beakers n ere used initially, the contents were transferred t o 100-nil. centrifuge tubes which were then placed in a bath of cold water for about 5 minutes, then centrifuged a t 2000 r.p.m. for 5 minutes. If t h e separation was good and t h e residue stable, the supernatant liquid Tyas either decanted or withdrawn by suction through a capillary tube. -4safer way was to withdraw the supernatant liquid by gentle suction through a filter stick consisting of an 8-inch thistle tube, having a 3-mm. stem and an 8-mm. bulb. The huib contains a wad of absorbent
EXPERIIIERTAL
The results of the two methods on a quantitative basis are shonn in Table I. I n general, the results obtained by the revised procedure are ___.___
_
Table I. P e r c e n t a g e of Cellulose O b t a i n e d f r o m Various F i b r o u s Materials Material Beet pulp Citrus pulp Corn stalks Mixed hay Beechwood Jimson weed stalk Poverty grass Timothy hay Cranberry pulp
h-orman-Jenkins Method 24 84 5 0 30 15 07 + 0 . 2 3 45 16 z 1 92 41.15 i . 0 . 4 0 54 62 i 0 . 1 5 45.81 1 0 . 2 6 45.90 i . 0 . 6 7 $ 3 . 5 6 i.0 . 3 7 52.20 5 0 . 0 3
Revised Method 28.21 5 0 . 1 3 1 5 . 8 3 i0 . 0 9 4 6 . 4 2 i0 . 4 9 40.37 1 0 . 2 8 53.20 5 0 . 0 6 44.30 0.01 42.18i0.21 44.88 5 0 . 1 1 54.76 ztO.26
