April, 1923
INDUSTRIAL A N D ENGINEERING CHEMISTRY
enters the tan vats. The chief precaution is that all pieces to be compared must be uniform at the time of taking the first gage readings. The pieces may then be put into actual yard liquors. A direct means is thus afforded of rating the plumping powers of tan liquors in actual use on a large scale. Using only ordinary care in the preparation of the test
377
pieces of skin, we found a deviation of only 40.07in testing the solutions described in Table I with different pieces of skin; in half the total number of determinations the differences were 0.03 or less. The method obviously may be applied to the determination of plumping power of any kind of solution.
An Improved Method for t h e Determination of Alpha-, Beta-, and Gamma-Cellulose* By M. W. Bray and T. M. Andrews FOREST PRODUCTS LABORATORY, DEPARTMENT OF AGRICULTURE, MADISON,WIS.
T
The following improved method for the determination of a-,p-, Wholly by difference- In HE determination of and y-cellulose, based upon the titrafion of organic material in order to Check the Percenta-,P-1 and Y-celluCross and Bevan cellulose, is more accurate and can be carried out ages of a-, P-, and T-cellulose is a measure of the resistance Of cellulose much more rapidly than the gravimetric method. It gives a direct lose in the gravimetric method, i t is necessary to to the action of 17-5 Per means for the estimation of cy-, p-. and y-cellulose. None of the cent sodium hydroxide.’ constants are obtained wholly by diflerence, as is fhe case in the repeat the Cross a d Bevan gravimetric method. Filtration and washing dificulties of the gravdetermination, which is The application of this dea long, ~ediousProcess. imefric method are practically overcome in the volumetric method. termination to Pulp cooked Check determinations can be made without repeating the Cross and The change in the graviby Various methods offers a means of evaluating these Bevan chlorination, as is necessary in the gravimetric method. metric method suggested pulps and possibly a way of by Opfermann,’o which showing the relation of one consists of washing the method of cooking to another and of establishing the charac- a-cellulose with dilute alkali instead of water in separating ter of the cellulose resulting from the cooking and bleach- i t from the nonresistant cellulose, gives more concordant ing processes.3 This determination affords valuable data also results, the separation appearing to be much more complete. in the study of decay of wood and wood pulp, showing the This improvement has beenused satisfactorily in connection change of resistant to nonresistant cellulose during decaya4 with the authors’ volumetric method. Practically the first work mentioned on the differentiation VOLUMETRIC METHOD of cellulose into a-, 6-, and y-cellulose is that of Cross and Bevan,6 who used this determination in the estimation Of Because of the difficulties in the gravimetric method and normal celullose. The method for the determination of to obviate the necessity of weighing, the oxidation method CY-, &, and y-cellulose cellulose obtained by the chlorina- proposed by Bronnert11 for “hemicelluloses” has been extion method, as worked out in the Cross and Bevana labora- tended and modified by the authors to provide a volumetric tory and described by Jentgen,’ with but slight modifica- method of analysis. tion, has been used in the Forest Products Laboratory for a Theoretically, cellulose is decomposed as follows upon oxidanumber of years, in connection with the chemical analysis of tion with potassium dichromate in sulfuric acid solution: American woods.8 It has also been used in the analysis of CsHloOs 602 = 6C02 5Hz0 cattle food consisting of hydrolyzed sawdustl9in the study of The calculations for the theoretical amount of potassium decay of wood and pulps,4 and in the study of the effect of dichromate necessary for the reaction, together with the bleaching of pulps,3 method of preparation of solutions, are given in Bronnert’s GRAVIMETRIC METHOD work. A number of difficulties and errors are encountered in the STANDARDIZATION OF POTASSIUM DICHROMATE SOLUTION gravimetric method of determining a-,@-,and y-cellulose. Since the potassium dichromate solution is to be used in This method necessitates careful washing of a- and @-cellulose to completely free them from impurities, and drying without oxidizing cellulose from pulps, it is standardized against decomposition is very difficult. Cumulative errors introduced cellulose obtained by the chlorination method12of Cross and in the determination of a- and @-cellulose are included in Bevan from sulfite pulp. The cellulose equivalent so obthe determination of y-cellulose, as this constant is estimated tained is used in preference to the theoretical value. Approximately 1 g. of cellulose (not corrected for ash), 1 Presented before the Division of Cellulose Chemistry at the 64th Meetdried at 105” C., is taken from a weighing bottle and placed ing of the American Chemical Society, Pittsburgh, Pa., September 4 t o 8, in a 250-cc. beaker. This is triturated with 30 cc. of 72 1922. * Jentgen, Z.Kunsfstoffe,1 (1911), 165; Piest, Z . angew. Chem., 26 (1913). per cent sulfuric acid and allowed to stand until solution is 24. complete. The sulfuric acid solution is transferred to a * Wells. TEISJOURNAL,13 (1921), 936.
+
Bray and Staidl, Ibzd., 14 (19221, 35. “Researches on Cellulose,” 1900-1910, Vol. 111, p. 23. 6 “Paper Making,” 1916, p. 97. Lac. cit.; W a g . Jahr., 67 (1911), 426; 2.ongew. Chem., 24 (1911), 1341; Schwalbe, “Chemie der Cellulose,” 1911, p. 637. 8 Ritter and Fleck, THISJOURNAL, 14 (1922), 1050; Mahood and Cable, Ibid.. 14 (1922). 727. * Sherrard and Blanco, Ibid., 13 (19211, 61 4
6
’
+
10 “Die Chemische Untersuchung pflanzlichen Rohstoffe und der daraus abschiedenen Zellstoffe,” translated by C. J. West, Paper, 8 (1921). 19. 11 “Die Chemische Untersuchung pflanzlichen Rohstoffe und der daraus abschiedenen Zellstoffe,” translated by C. J. West, Paper. 18 (1921), 21; Schwalbe and Sieber, “Die Chemische Betriebskontrolle in der Zellstoff und Papier Industrie,” p. 151;Schwalbe, “Chemie der Cellulose,’’ 1911, p. 637. 1* Schorger, TEIS JOURNAL, 9 (1917), 556.
378
”01. 15, No. 4
INDUSTRIAL A N D EhlGINEERING CHEMISTRY
100-cc. graduated flask. The beaker is washed several times with 72 per cent sulfuric acid to insure complete removal of the dissolved cellulose. The flask is filled to the mark with 72 per cent sulfuric acid and thoroughly mixed. To a 10-cc. portion of the dissolved cellulose, 10 cc. of potassium dichromate solution (containing approximately 90 g. per liter) and approximately 60 cc. of 72 per cent sulfuric acid are added. The solution in the beaker is boiled for exactly 5 min., cooled in ice, and titrated with ferrous ammonium sulfate solution (containing 159.9 g. per liter), using potassium ferricyanide as an indicator. The titration is conducted in the usual way and the point where a drop of the titrated solution gives a blue color with a drop of the indicator is taken as the end-point of the titration. The relative value of ferrous ammonium sulfate solution to the dichromate solution is established by titration in the usual way. PROCEDURE FOR DETERMINATION OF CELLULOSES One gram of dry Cross and Bevan cellulose or sample of pulp is weighed into a 250-cc. beaker and triturated with 25 cc. of mercerizing liquid (17.5 per cent sodium hydroxide solution) until the mass is homogeneous, and allowed to stand for 30 min. The contents of the beaker are filtered with suction through an alundum (porosity R. A. 98) or a Gooch crucible. After the insoluble cellulose is sucked practically dry, it is loosened with a glass rod and washed, first with 4 per cent sodium hydroxide solution (50 cc.) and then with approximately 300 cc. of cold distilled water in small quantities. Since the a-cellulose is dissolved in 72 per cent sulfuric acid, it is not necessary to wash it free from sodium hydroxide, which would be very difficult in cellulose containing a high percentage of P-cellulose. In some cases it is impossible to separate the alkali-insoluble and alkali-soluble cellulose (a- and @-cellulose)by filtration through an alundum crucible, as the cellulose mass becomes very jelly-likeg because of the presence of 0-cellulose. I n such cases the alkalitreated cellulose is placed in tubes and centrifuged until the a-cellulose separates a t the bottom of the tube. The supernatant liquid is decanted from the a-cellulose and successively washed by decanting and centrifuging, first with 4 per cent sodium hydroxide solution (50 cc.) and then with distilled water, until the total washings approximate 350 CC. a-cELLuLosE-The alkali-insoluble or a-cellulose is removed from the alundum crucible with a pointed glass rod and placed in a 250-cc. beaker. The filtrate is used for the pand y-cellulose determination. It is then dissolved in approximately 30 cc. of 72 per cent sulfuric acid, transferred to a 100-cc. graduated flask by washing successively with portions of the acid, and fUed to the mark. A 10-cc. sample is pipetted into a 250-cc. Pyrex beaker, to which are added 10 cc. of standard dichromate solution and approximately BO cc. of 72 per cent sulfuric acid. The oxidizing mixture is boiled gently for exactly 5 min. and cooled in ice, and the excess dichromate is titrated with ferrous ammonium sulfate solution, as described under “Standardization of Potassium Dichromate Solution.” 0-PLUS y-CELLuLosE-The 350-cc. alkaline filtrate containing the 0-and y-cellulose, remaining from the alkaliinsoluble or a-cellulose determination, is diluted to exartly 400 cc. This is divided into two equal parts. One 200-CC. portion, which is left alkaline, is diluted to 150 cc. in a graduated flask. A 25-cc. portion of this solution is pipetted into a 250-cc. beaker. To this are added 5 cc. of the standard dichromate solution and 60 cc. of 72 per cent sulfuric acid. The contents of the beaker are boiled for exactly 5 min., cooled in ice, and titrated as described under the a-cellulose determination, From this titration the sum of the percentages of 0-and y-cellulose is calculated.
@hLLuLosE-The remaining 200 cc. of the alkaline filtrate from the a-cellulose determination are acidified with 10 per cent sulfuric acid solution, using one drop of dilute methyl orange as indicator, adding 5 cc. of this acid in excess, and diluting to 250 cc. in a graduated flask. This procedure almost immediately precipitates the 0-cellulose. The flask is allowed to stand for several hours, or until the P-cellulose coagulates and settles to the bottom. A 25-cc. portion of the supernatant liquid is pipetted from the flask and treated as described under the 0-plus y-cellulose determination. From this determination the percentage of 7-,or soluble, cellulose may be calculated. @-CELLuLosE---The percentage of 0-cellulose is obtained by subtracting the result of the y-cellulose determination from the result of the 0-plus y-cellulose determination.
RESULTS EXPERIMENTS 1 AND 2-Table I gives the results of the analyses of cellulose obtained from Samples 37 and 45, which represent spruce sulfite and aspen soda pulps, respectively. They show how closely duplicate determinations can be made. TABLE I-VOLUMETRIC Sample No. 37 45 2548
D r y Weight of Sample I.. 000
1.000 0 9473 0.9473
ANALYSESO F
SPRUCE PULPS
8-
Cellulose
Cellulose
7Cellulose
71.5 72 2 78.6 78.7 77.3 77.5
15.1 15.1 17 9 17.4 12 8 12 5
11.6 11 6 3 8 3 8 8 1 8 4
a-
%
%
%
EXPERIMENT 3-Two portions of spruce sulfite pulp of 0.9473 g. each (dry weight), containing 96.75 per cent of cellulose, were analyzed for a-, p-, and y-cellulose. These constants were determined in the pulp without first obtaining cellulose by the modified Cross and Bevan method. The results are given in Sample 2548 of Table I. EXPERIMENT 4-Analyses were made on spruce sulfite pulp (Sample 2548). The results (Table 11) show that the volumetric or oxidation method gives results comparable with those obtained by the gravimetric method. Analysis 1 was carried out by the gravimetric method. Analyses 2 to 9 are check volumetric analyses, made on separately chlorinated samples. TABLE11-COMPARISONOF VOLUMETRICAND GRAVIMETRIC ANALYSESOF Analysis No.
SPRUCE PULP(SAMPLE 2548) a a8-
Dry Weight of Sample
Cellulose
%
Cellulose
Cellulose 7-
%
%
16.1
8.0
16.3 17.0
8.4 7.8
6 7
13.6 15.8 14.4
8.1
1.0682 0.9605 0,9624
74.6 74.6 77.6 77.0 77.0 75.0 77.6
8
0.9579
i6:2
13 8 _. -
15.5
9
0,9767
75.9
8.9 9.2 9.4 10.4 8.6
Gravimetric Melhod 1 2 3 4 5
1.8925
.
1 0000 0.9575 1,0572
76.00
Volumetric Method
77 2
14.2
s.2 8.X 8.3
AVERAGE 76.3 15.1 a Complete analysis of this pulp is given in THISJOURNAL, 1 4 (1922), 35, Table IV. The data for Analysis No. 1 for a-,8-, and -f-ce,llul?se, !n the present paper, were determined after the effect of over-chlormatlon in the process of isolation of the cellulose was more thoroughly understood and controlled, and therefore differs somewhat from the earlier values.
I n THIS JOURNAL, 15 (1923), 19, there appeared a note relative to a new heat- and chemical-resisting enamel. Since then it has been brought t o our attention that such white enamels made in other plants have been on the market for some time, and if the impression was given that the enamels there described were the first and only ones with such characteristics, it is an J error.- [EDITOR
