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),
(8)
Introducing 8 into 6 leads to t h e result
(1
(NH,OH), = ",OH
+ L.Ch)
(9)
Now t h e ratio of the initial and final hydrogen ion concentrations is from Equation 1: H -
Ho
--
(",OH), +XH,OH X(+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
h-orman-Jenkins Method
Beet pulp Citrus pulp Corn stalks Mixed hay Beechwood Jimson weed stalk Poverty grass Timothy hay Cranberry pulp
24 84 5 0 30 15 07 0.23 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.0.67 $ 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 3 ~ 0 . 2 6
V O L U M E 2 4 , N O . 9, S E P T E M B E R 1 9 5 2 Table 11. Percentage Content of Lignin and Furfuraldehj-de i n Cellulose 31aterial A1iut.d hay Beechwood . J i m o n stalk 1’0 vert y p r a w Tiiiiot h l - hay
_ _ ~ ~
~
~~~~
Norman-Jenkins Method Lignin Furfural 3.84 13.20 1.18 16.11 1.34 13. 1.5 3 02 18 49 3 77 15.08
~~-~
Revised ?iIetli& Lignin Furfilial 1.95 13 12 0 20 14.44 1.06 1.5. 68 2.13 17.84 1.64 15.78
1511
A partial chemical analjsib of the cellulose obtained by each method, shown in Table 11, indicates the degree of similaritv of the products on a qualitative basis. The results obtained indicate that although the SormanJenkins cellulose may retain a slightlv greater percentage of furfuraldehyde, the iesult- are of the same general order Invariably, the h~orman-.JenI,in~crllulose contained the highri percentage of lignin.
.~~
slightly higher than those obtained by the Sornian-Jenkins method. T h e degree of precision is generally considerably greatel,. I n the initial treatment, it was found advantageous to conduct the chlorite reaction in 150-ml. beakers. The chlorite treatment apparently serves much the same purpose as the alternate treatments n-ith hypochlorite and sulfite and results in the elimination of t h r laborious steps involved in performing the usual type of fiitrationa. The ultimate use of the acid hypochlorite-sulfitr treatment is highly desirable since this reaction is the basis of the lIaul4 test. OrdinarilJ-, two treatments with the acid hypoclilox,ite render5 a samlilc substantially lignin-free.
LITERATURE CITED
(1) Holland, E. B.. Reed. .J. r . , and Huckley, .J. P...JI ., .J. A g r . Reseurch, 6 , 101-13 (1916). ( 2 ) lIatrone, G., Ellis, G. H.. and Maynard, L. A , . J . A n f m u / S c i ’ . , 5, 305-12 (1946). ( 3 ) Sorman, A. G., and .Jellkitis, S. H , , Biocheui. .I.. 27, 818-31 (1933). (4) Taylor, AI, C., et ul., ISD. ENG.CHEM.,32,899-903 (194U). RECEIVED f o r review January 31. 1932. .iccelited .June 30, 1952. Contribution 827 of the llassachosetts Agricultural Experiment Station, Amherst. Mass.
Chemical and Cryoscopic inalysis of p-Propiolactone WILLARD P. TYLER AND DONALD W. BEESING T h e B . F . Goodrich Research Center, Brecksville, Ohio ‘ 0 UETHODS of analysis of 8-propiolactone for purity or f i r impurities have been reported prior t o the use of the reaction of t,he lactone with thiosulfate ion for kinetic studies (5). ;1 study of the kinetic data and of other possible analytical reactions disclosed in a series of papers (6-9) indicated t h a t two rendily dctermined ions, thiosulfate and iodide, react rapidly enough with the lactonc t o serve as useful analytical reagents. 3Iethods have been used in this laboratory involving each reagent. However, a cletailed discussion is given here only for the thiosulfate ion method, since it, is the most precise and most readily controlled procedure for determination of purity of crude and purified 0-propiolactone. The conditions necessary for quantitative reaction under the variety of sample conditions normally encountered in working Lvith this material n-ere found t o require more accurate specification than was anticipated from the report of Bartlett and Small (3).
The chemical method has been verified as being somewhat less than st)oichionietric by determination of puritg by the cryoscopic mcthod. Procedures adapted from known methods of determination of the commonly found impurities, acrylic acid and acetic anhydride, arc included herein. DETER3IIN.4TION OF 0-PROPIOLACTONE
Reagents. Sodium thiosulfate, approximately 0.4 M . Standard iodine solution, 0.2 S. Dibasic potassium phosphate buffer solution, K2H1’04,2 J I and 4 N , Sodium acetate, 1 M . Starch solution, 0.5%. Procedure. Case I, for 60 to 100% p-propiolactone containing l c ~ sthan 20yG acid calculated as acrylic acid. This case covers all crudc and purified samples normally encountcred. Pipet 25 ml. of 0.4 -11sodium thiosulfate into a flask and add 2 niillimoles of the phosphate buffer solution. Add not more than 0.5 gram of sample to contain about 5 millimoles (0.3 to 0.4 gr:im) of lactone from a dropping bottle or by weighing into a vial. Swirl gently to dissolve and allow it to stand for 10 to 20 minutes. S o dilution must take place prior to the reaction Iwriod, hecause of t,he effect on the reaction rate. At the end of the reaction period mash down the sides of the flask with about
25 ml. of water and titrate with 0.2 11’ iodine solution using starch indicator. Case 11, for samples containing 40 t o 80% lactone, but 20 to 60% acid calculated as acrylic acid. Use 6 millimoles of phosphate buffer and a sample size of 0.4 to 0.6 gram of sample (not t o exceed 0.4 gram of lactone). Case 111, for samples containing 10 to 40% lactone and 60 to 90% acid calculated as acrylic acid. Use 12 millimoles of phobphate buffer, adding it as solid or 3 ml. of 4 M solution. Use a sample size of 0.6 t o 0.8 gram (not to exceed 0.4 gram of lactone). BLAKKS. 811 blanks should be run so as t o simulate actual run conditions to correct for minor errors which may occur when thiosulfate is titrated in weakly alkaline solution. I n case I and 11, add 5 millimoles of sodium acetate before titration. I n case 111, add 5 millimoles of sodium acetate and 8 millimoles of acetic acid, adding the acid last.
% P-propiolactone
=
( A - B ) iV X 7.206 I T X 0.995
il = ml. of iodine required for blank B = ml. of iodine required for run A- = normality of iodine
I.V = weight of sample The correction factor, 0.995, is discussed below. DETERMINATION OF ACRYLIC ACID IN (3-PROPIOLACTONE
This method is an adaptation of a known method ( I O ) for determination of unsaturation particularly useful for organic comIt is equally applicable to pounds containing a vinyl group. determination of acrylic acid in many other compositions Reagents. Potassium bromate-potassium bromide, approximately 0.1 S (2.79 grams of K B r 0 3 and 12 grams of KBr per liter). Sodium thiosulfate, 0.05S. Sulfuric acid, 10%. Mercuric sulfate, 576 in 10yc sulfuric acid. Sodium chloride, 10%. Potassium iodide, 15%. Starch solution, 0.5%. Procedure. Pipet 25 ml. of 0.1 S potassium bromate-potassium bromide solution into a 500-ml. iodine flask. Add the sample, which must not contain more than 1.25 milliequivalents (45 mg.) of acrylic acid, from a dropping bottle and swirl the flask to dissolve. Immediately add 10 ml. of 10% sulfuric acid, stopper n i t h a water seal, snirl only enough to mix, and allom it to stand for 3 minutes. Add 10 ml. of 5Y0 mercuric sulfate solution around the stopper in such a way as to avoid loss of bromine. Swirl occasionally over a 5-minute period, maintaining a tight stopper n-ith a n-ater seal. If the solution is colorless or very pale
