T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMIXTRY
32
Vol. 14,No. 1
The Swelling and Gelation of Gelatin' By Robert H.Bogue MELLONINSTITUTE OF INDUSTRIAL RESEARCH, UNIVERSITY OF PITTSBUROH, PITTSBUROH, Pa.
In several papers by Martin Fischer and his collaborators*
These silicates were made up into two series, one containing 2 per cent of NazO throughout, with consequently varying lution in mixtures of the salts of polybasic acids increases amounts of SiOz, and the other containing 4 per cent of SiOa progressively as the amount of acid or alkali in these mixtures throughout, with varying amounts of NazO. It has p r e is increased from a given low point. They find further that viously been shown6that solutions of the silicates of sodium the highest degree of swelling is obtained in the pure acid which contain equal amounts of NazO by weight, but varying solution, that this decreases to a minimum in a solution con- amounts of SiOn, do not possess the same concentration of sisting essentially, for example, of monosodium phosphate, hydroxyl ion, but that the latter increases as the ratio of and that the swelling again increases on the alkaline side of soda to silica in the molecule increases. The make-up of the two series, together with their pH this point through the di- and the trisodium phosphates to the pure alkali, at which point it is nearly as high as in the values, is shown in Table 11. pure acid. In other words, gelatin swells the least, and is TABLE 11-COMPOSITION OF SILICATE SERIES not liquefied, in a solution of monosodium phosphate, a Series 1 Per cent Per cent solution of about equal parts of monosodium and disodium NUMBVR NazO Si02 pH (0.01M) citrate, and a solution of pure sodium bicarbonate. As the 1 2.0 7.7 10.80 2 2 . 0 6 . 7 10.90 solutions become either more acid or more alkaline the swell3 2.0 5.7 11.08 4 2.0 4.8 11,16 ing is increased, and they tend ever more strongly to liquefy. 5 2.0 4.1 11.50 It would seem that the above effects were controlled by the 6 2.0 11.95 3.2 2 . 0 7 2 . 1 12.43 hydrogen-ion concentration of the solution. Patten and 2.0 8 13.57 0.0 Johnson,3 in repeating a part of the work of Fischer and his Series 2 1 1.1 4.0 10.68 collaborators, have shown that the region of least smelling 2 1.2 4.0 10.79 3 1.4 4.0 10.98 and of least tendency to go into solution corresponds with a 4 1.7 4.0 11.11 pH value of from 4.4 to 5.7. These values correspond 5 2.0 4.0 11.50 6 2.5 4.0 12.08 reasonably well with the findings of Loeb4that the minimum 7 3.7 4.0 12.62 degree of swelling, viscosity, osmotic pressure, alcohol .In the first experiment small portions of the silicates were number, and conductivity all fall very close to, or directly at, added in successive stages to the sol of a high-grade gelatin the isoelectric point, which is for gelatin pH=4.7. Another conception which has long been given credence to of such concentration that the final product contained always account for the causes of the alteration in the properties of 3 per cent of gelatin. The relative consistency only was meagelatin under the influence of electrolytes is that the size sured. The results &re tabulated in Tables I11 and IV. of the charge on the cation or the anion is the dominant TABLE 111-EFFBCT OP SILICATE SERIES1 ON LIQUEPACTION OF GELATIN (5 cc. 8 pet cent gelatin + 4 cc. water- a) influence. The experiments of Fischer are nonconclusive in COMPOSITION OF MIXTURE STATE this respect, although Fischer himself refers to the changes as NUMB€DR 1 a + 1.0 cc. water (control). Solid being brought about by acids knd alkalies. He avoids a a + 0.5 CC. water + 0.5 CC. Silicate 1 2 Solid 3 a + 1.0 cc. Silicate 1 Solid consideration, however, of hydrogen-ion concentration as 4 Solid a + 0.5 cc. Silicate 1 + 0.5 cc. Silicate 2 5 a + 1.0 CC. Silicate 2 Solid distinguished from what is generally referred to as acidity 6 a + 0.5 cc. Silicate 2 + 0.5 cc. Silicate 3 Solid or alkalinity. 7 a + 1.0 cc Silicate 3 Solid a + 0.5 cc. Silicate 3 + 0.5 cc. Silicate 4 Solid 8 In connection with some work upon the effect of silicates 9 a + 1.0 cc. Silicate 4 Solid 10 Solid a + 0.5 cc. Silicate 4 + 0.6 cc. Silicate 5 of sodium on the properties of gelatin, the writer has obtained 11 a + 1.0 cc. Silicate 5 Solid data which seem to indicate that the variation in hydrogen12 Semisolid a + 0.5 cc. Silicate 5 + 0.5 cc. Silicate 6 13 a + 1.0 cc. Silicate 6 Semisolid ion concentration and the valency of the combined ions may Semisolid 14 a + 0.5 cc. Silicate 6 + 0.5 cc. Silicate 7 15 a + 1.0 cc. Silicate 7 Ljquid be adequate to account for all variations in properties which 16 a + 0.5 cc. Silicate 7 + 0.5 cc. Sodium hydroxide 8 Liquid are observed. Liquid a + 1.0 cc. Sodium Hydroxide 8 17
it has been shown that the tendency of gelatin to go into so-
EXPERIMENTAL
OF SILICATE SERIES 2 TABLE IV- -EFFECT
The silicates of sodium6which were used consisted of seven of varying composition as follows: No. 1 2 3 4 5 6 7
TABLEI-COMPOSITION OF SILICATES OP SODIUM Per cent Per cent Per cent Approximate HzO Molecular Structure NazO SiOz 66.1 Naz0.4SiOz.33HzO 7.0 26.9 NazO 3 5SiOz 23Hz0 30 3 60.72 8.98NaaO 3Sioz 18Hr0 31 2 57.8 11.0 53.4 Naz0.2 6SiOz 13Ha0 13.7 32.9 45.72 NazO 2Si02 9Hr0 17.83 36 45 37.5 NazO.1 5SiOz 51x20 24.2 38.3 44.2 NazO.SiOz ? l a 0 26.95 28.85
\
1 Presented before the Division of Physical and Inorganic Chemistry a t tbe 62nd Meeting of the American Chemical Society, New York, N. Y., September 6 to 10, 1921. 2 Fischer, Hooker, Benzinger, and Coffman, Science, N. S., 46 (19171, 189; Fischer and Hooker, J. Am. Chem. Soc., 40 (1918), 272; Fischer and Coffman, Ibid., 40 (1919>,303. * J . B i d . Chem., 88 (1919), 179. 4 J . Gen. Physiol., 1 (1918-19), 39, 237, 363, 483, 559. ' 8 The author is indebted to the Philadelphia Quartz Co. for the silicates experimented upon. The analyses of these samples were furnished by William Stericker (Mellon Institute).
+
NUMB= :R 1 2 3 4 5 6 7 8 9
10 11 12 13 14 15
++ a + a + a + a + a + a+ a + a + a + a + a + a + a + a a
ON
LIQUEFACTION OF GELATIN
(5 cc. 6 per cent gelatin 4 cc. water-a) COMPOSITION OF MIXTURE 1.0 cc. water (control) 0.5 cc. water 0.5 cc. Silicate 1 1.0 CC. Silicate 1 0.5 cc. Silicate 1 0.6 cc. Silicate 2 1.0 cc. Silicate 2 0.5 cc. Silicate 2 0.5 cc. Silicate 3 1.0 cc. Silicate 3 0.5 cc. Silicate 3 0.5 cc. Silicate 4 1.0 cc. Silicate 4 0.5 cc. Silicate 4 0.5 cc. Silicate 5 1.0 cc. Silicate 5 0.5 cc. Silicate 5 0.5 cc. Silicate 6 1.0 cc. Silicate 6 0.5 cc. Silicate 6 0.5 cc. Silicate 7 1.0 cc. Silicate 7
+
+ + + + + +
STATE Solid Solid Solid Solid Solid Solid Solid Solid Solid Semisolid Semisolid Liquid Liquid Liquid Liquid
IMPROVED PRocEnuRE-In order that more comprehensive data might be obtained a more elaborate procedure was adopted. Cylindrical glass funnels about 25 mm. in diameter and 80 mni. in height were fitted with filter paper, and the outlet tubes were closed by a short sealed piece of rubber tubing. Into these was introduced an excess of the several silicate solutions described, the temperature being about 8
R. H . Bogue, J. Am. Chem. Soc., 42 (1920), 2575.
,
Jan., 1922
THE JO URXAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY
10" (2. One-gram portions of the gelatin which had been ground so as to pass a 40-mesh, but retained by a 60-mesh, sieve were poured into each funnel and stirred. After an hour the excess of liquid was drawn off, the gelatin washed by several perfusions of distilled water, and the swellingmeasured direct>lyin millimeters to which the gelatin rose in the tube. The gelatin was then transferred t o small beakers, water was added, and the gelatin brought into solution by warming. Each sample was made up to 100 cc., e. Q., a 1 per cent solution, and the viscosity, alcohol number, jelly consistency, and hydrogen-ion Concentration were determined.
33
centrated sulfuric acid, and water containing a little barium chloride. The gas chain and the hydrogen purifying chain were enclosed in an air thermostat set at 30" C. The average deviation during measurements was not greater than *O. 02 O . The measurements were made by the use of a Leeds and Sorthrup type K potentiometer. The value of pH was calculated from the electrode potential by the equation pH=- E-0.337 0.0601 '
which was derived from the well-known formula of Nernst:
E=Eo
+ RT -loge
C,
nF SOLID SEMI-
%LID LlQLlID
J E L L Y CONSISTENCY
I I
> 160
t
xx
5
150
LL
0
5 w
2 140 LL
s
I
50
p 45 i d 40
s
35
Q
0 LL
ul 30 w W t 25
5r!
20
E 15 + H VALUE OF GELATIN SOLUTION FIO. I-TAE
JELLYCONSISTENCY, VISCOSITY, AND SWELLING OR GELATIN AT VARYING pH VALUES. (TABLEVI, SERIES1)
Viscosity-The viscosity was measured by an Ostwald viscosimeter immersed in a water thermostat set at 35 O C. This temperature was selected for the viscosity measurements in order that no complications due to an equilibrium between what C. R. Smith' calls the sol form A and gel form R might arise. At 35" the sol form only can exist. The figures given are obtained by dividing the time in seconds for the outflow of the gelatin by the corresponding time for water a t the same temperature. Alcohol nuiriber-The alcohol number is taken as the number of cubic centimeters of 95 per cent alcohol which are required to precipitate or produce a definite turbidity in 5 cc. of the gelatin sol at 30" C. JeZZy consistency-The jelly consistency was noted by allowing 10 cc. of the gelatin-silicate mixtures to stand for 12 hrs. a t 10' C. Only three degrees of consistency were observed: solid, semisolid, and liquid. H-ion concentration-The hydrogen-ion concentration was determined by electrometric means. The hydrogen cell was of 1he type suggested by Clark.* Tenth-normal calomel cells, which were made up with great care, were employed. The hydrogen was supplied from a commercial tank and purified by passing through alkaline permanganate, con-
' J . Am. Chem. SOC.,4 1 (1919),135,THISJOURNAL,12 (1920),878. 8
J . Bid. Chem., 28 (1915),475.
where pH is the log of l/hydrogen-ion concentration, E the electrode potential a t concentration C, Eo the electrode potential a t molar concentration, R the gas constant, T the absolute temperature, n the valency of the ion, F the Faraday constant, and C the ionic concentration of the solution. TESTS O N NORM.4L GELATIN-The data obtained by using the gelatin in the normal condition are shown in Table V. TABLEV-EFFECT OF SILICATES ON PROPERTIES OF NORMALGELATIN Per Per Coefficent cent cient of Alcohol Jelly No. NaeO Si02 Smelling Viscosity Number Consistency pH Series I Solid 5.8 0.0 0.0 20 1.41 8 1.49 Solid 7.9 23 2.0 7.7 37 Solid 8.5 25 40 1.51 2.0 6.7 Semisolid 8.6 26 1.63 2.0 5.7 45 Semisolid 8.7 26 1.58 2.0 4.8 47 25 Semisolid 9.1 47 1.61 2.0 4.1 Liauid 9.5 26 3.2 44 1.57 2.0 27 Liquid 9.6 2.0 2.1 44 1.55 Liquid 9.9 29 43 1.48 2.0 0.0 Series 2 Solid 5.8 20 1.41 8 0.0 0.0 Solid 7.5 1.48 20 34 1.1 4.0 1.50 22 Solid 7.9 38 4.0 1.2 1.52 24 Solid 8.2 42 1.4 4.0 25 Semisolid 8.4 45 1.58 4.0 1.7 25 Semisolid 9.1 47 1.61 4.0 2.0 Liquid 10.0 1.59 46 27 4.0 2.5 30 Liquid 10.8 43 1.49 4.0 3.7
TESTS O N ISOELECTRIC GELATIN-The above experiments were repeated, but instead of the gelatin in its normal condition, which was essentially calcium gelatinate of a pH of 5.8, the gelatin used was first rendered isoelectric by allowing it to soak for an hour in N/l% hydrochloric acid and filtering and washing oht the excess of acid by several perfusions with distilled water. The pH value of a 1 per cent solution was found to be 1.7, which is the value of gelatin a t its isoelectric point. The data are shown in Table VI. TABLE VI-EFFECT
.
No.
Per cent NaaO
0 1 2 3 4 5 6 7 8
0.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 0.0 1.1 1.2
1.4 1.7 2.0 2.5 3.7
OF SILICATES ON PROPERTIES OF ISOELECTRIC GELATIN Per Coefficent rient of Alcohol Jelly Si02 Swelling Viscosity Number Consistency pH Series 1 4 Solid. 4.7 0.0 17 1.33 24 Solid 7.5 42 1.52 7.7 46 1.58 25 Solid 8.1 6.7 2.5 Solid 8.2 4s 1.59 6.7 1.61 26 Semisolid 8.3 45 4.8 25 Semisolid 8.8 49 4.1 1.66 26 Semisolid 8.9 51 1.66 3.2 30 Liquid 9.1 49 2.1 1.65 44 1.57 Liquid 9.4 32 0.0 Series 2 4 Solid 4.7 17 1.33 0.0 23 Solid 7.1 39 1.47 4.0 Solid 7.5 41 1.49 24 4.0 Solid 7.8 44 1.56 24 4.0 46 1.58 25 Solid 8.1 4.0 49 1.66 25 Semisolid 8.7 4.0 30 Semisolid 9.6 48 1.64 4.0 Liquid 10.4 46 1.59 35 4.0
.
In Fig. 1, the jelly consistency, viscosity, and swelling of Series 1 in Table VI are plotted against the pH values. UISCUSSION An inspection of the data presented in the several tables and in the figure brings out many points that are of interest. The swelling is found to progress regularly in Series 1 with decreasing silica content, the percentage of soda present being held constant, and in Series 2 with increasing soda
THE JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
34
content, the silica in this case being kept constant. This increase in swelling does not continue throughout the entire extent of the series, however, but reaches a maximum beyond which it drops slightly. The coefficient of viscosity is found to behave in an entirely similar manner, as would be expected from the findings previoudy reported0 which have shown that solution and viscosity are parallel functions, and swelling is a measure of solvation. If the hydrogen-ion concentration were not simultaneously determined it would be assumed that, in Series 1, the variation in swelling and viscosity were directly attributable to the regular variation in the percentage of silica present, since the soda content remains constant. But the pH values are found to increase regularly also, and this increase cannot conceivably be attributed to the decrease in silica content per se, because the silicic acids have many times been shown to be un-ionized. The only conclusion which may be drawn to account for the increase in the pH value is that as the content of silicic acid in the molecule of the sodium silicates decreases the sodium hydroxide actually present in an ionized condition increases. And this in turn may be brought about only by a continually increasing degree of hydrolysis of the silicates with increasing ratio NazO: SiOl. Furthermore, the differences in degree of hydrolytic dissociation on passing through the silicate series must be considerable in order to account for the wide variation in pH, e. g., in Table VI, Series 2, from No. 1 (pI-I=7.1) to No. 7 (pH=10.4). These results are in complete accord with, and therefore tend t o confirm, the conclusions reported in an earlier paper,1° to the effect that the hydrolysis of the silicates of sodium increases as the ratio of Na2O to Si02in the molecule increases. The alcohol number is found to rise regularly with increasing pH, and might conceivably be utilized for the purpose of roughly locating the hydrogen-ion concentration of a solution of gelatin. The jelly consistency is solid at the lower pH values, but in the neighborhood of pH=8.5 a softening is observed, while a t a pH of about 9.5 the gelatin will no longer gel a t 10'. The relation of the jelly consistency to the swelling and the viscosity should be especially observed. At the point where the maximum swelling and viscosity are attained the jelly is no longer firm, but has become soft. This is well illustrated in Fig. 1. On further increases in pI-1, swelling and viscosity begin to decline, and the gelatin, at the concentration used, remains liquid. This has an important bearing on the explanation of the mechanism of gelation. As the gelatin is brought into the presence of increasing quailtities of sodium hyroxide, constantly increasing amounts of gelatin ccill, according to L0eb4 be converted into sodium gelatinate. This gelatinate is shown to possess a strong tendency towards solvation, e. g., it ewells to a considerable extent. But it also is much more soluble, according t o Loeb, than gelatin per se and so will not, gel under the Conditions of our experiment. But may gelation, and precipitation or coagulation, be ' regarded as identical? In othrr words, is gelation dependent primarily upon solubi?ity? There is no douht that gelatin at its isoelectric point iF actually much less soluble than under any other electrical condition. A white, almost granular, precipitate may be obtained by bringing gelatin to that condition. But the writer has data which show that the consistency of the jelly under those conditions may actually be less than a t slight intervals on either side of that point. Gelation appears rather to be due t o an increase in the solvation or hydration of the dispersed particles while true precipitation and coagulation take place only under conditions of excessive dehydration. That solvation and viscosity run B
R. H. Bogue, J . A m . Chcm. Soc., 48 (1821),1764. 43 (1920),2576.
10 Ibid.,
Vol. 14, No. 1
parallel has already been shown,gand the fact that the viscosity a t 30" begins to drop when the liquid a t 10' will no longer solidify is significant. Swelling is known to be increased by low temperatures, and viscosity is also increased by low temperatures. Gelation is similarly influenced, which means that solvation is much greater a t low than at high temperatures. All of our data confirm this point of view. Since the volume occupied by the dispersed phase is very nearly defined by the degree of solvation, the size of the molecule, e. g., the volume occupied by unit weight of dispersed phase, will be the determining factor in both the degree of swelling, the viscosity, and the jelly consistency of the gelatin. This statement must not be construed to mean, however, that the greater the volume per unit weight of gelatin the greater also will be the value of each of the above properties indefinitely. If this volume is very small, then the three properties under discussion will also he small; if this volume be very large then, it being mostly water, the consistency and viscosity will again be emall, and as the conditions which make for increased size also make for increased solubility (e. g., gelatin chloride and sodium gelatinate are more soluble than gelatin) a point must be eventually reached beyond which further additions of acid or alkali will result more in favor of solution than of increased size from hydration. But at intermediate values the degree of each of these properties reaches its maximum. The effect of the silicates upon the properties of the isoelectric gelatin is quite similar to that observed in the normal gelatin (calcium gelatinate). The swelling and viscosity are somewhat higher in the isoelectric series, but this is probably due, as Loeb has found in similar cases, to the fact that calcium gelatinate exhibits a lower degree of swelling and viscosity than sodium gelatinate, and that the presence of the divalent calcium ion retards the greater activity of the monovalent sodium ion in this respect. By rendering the gelatin isoelectric and washing it RS described, the calcium ion is largely removed. SUMNARY
Experiments have been conducted upon gelatin sols and gels that have been treated with silicates of sodium in which the ratio of Nan0 t o Si02 in the molecule varied regularly from 1:4 to 1: 1. The solutions were made up so that the actual amount of Na20 was constant in one series, while the actual amount of Si02 was constant in the other series. The degree of swelling, viscosity, alcohol number, and pH value were determined in each series, both upon the normal gelatin, which was essentially calciuin gelabinate of a pH of 5.8, and upon the gelatin which had been rendered isoelectric and had a pH value of 4.7. The data obtained show that the swelling and the viscosity increase, in Series 1, with a decrease in the silica content, the percentage of soda being held constant. The pH value is shown to increase constantly, however, as the ratio Na20:Si02increases. This is due to an increase in the degree of hydrolysis of the silicates. The variation in the above-mentioned properties appears to be dependent upon the pH value, rather than upon the changing silica content. This is further evidenced by the similar behavior of Series 2, in which the silica content remains constant. The swelling and viscosity reach their maximum value a t a pH of about 8.5, and decrease slightly a t higher values. The jelly consistency, however, is solid at pH values between 4.7 and 8.0, but at 8.5 it becomes soft, and liquefies a t 9.0 and above. This affords the basis of an argument which concludes that gelation is due to and dependent upon the tendency of the substance to become solvated, the volume occupied by unit weight of dispersed phase being the determining factor. When this volume is very small or very
Jan., 1922
THE JOURhrAL OF IhTDUSTRIAL AND ENGINEERIlVG CHEMIXTRY
larg,e the jelly coiisistency will be small, and, a t intermediate values of volume per unit weight, the jelly consistency will rearh its maximum. The results upon isoelectric gelatin are similar to those obtained with normal gelatin, except that higher degrees of
35
swelling and viscosity are attained, because of the absence of the retarding divalent calcium ion. The alcohol number is found to rise regularly with increasing pH, and it is suggested that this value may be utilized for rough measurements of pH.
The Chemical Changes Involved during Infection and Decay of Wood and Wood Pulp’ By Mark W. Bray and Joseph A. Staidl FOREST PRODUCTS LABORATORY, u. s. DEPARTMENT OF AGRICULTURE, MADISON, WISCONSIN
A knowledge of the chemical composition of woods and pulps, linked with a study of the changes in composition after infection2 with specific organisms of molds and wooddestroyers, is of considerable importance in that it throws further light on the astonishing losses sustained through the decay of wood and pulp and in the pulping and conversion into paper of such infected wood and pulp. A mere study of the organisms of decay, without a thorough investigation of the chemical changes involved, would help but little in solving the problem, because an infected log or lap of pulp may look more or less sound and yet contain wooddestroying fungi which have chemically changed the cellulose, rendering it very much less resistant. By the study of the chemical changes involved, the progress of decay may easily be followed, and the cause of the large losses in pulping infected woods may also be explained. The methods of analysis, with the exception of the determinations of lignin,3 solubility in 7.14 per cent sodium hyand copper number6 &oxide4 (a-,@-! and y-cell~loses),~ were those described by A. W. Schorger’ in the “Analysis of Some American Woods.” The methods used were chosen with the purpose of following the progress of decay of wood and pulps, and of obtaining data, if possible, which would aid in ascertaining the chemical changes which these substances undergo during decay. It was also hoped to explain the effects of decay on the yield, quality, and pulping characteristics of wood by the mechanical, sulfite, and soda processes. The cellulose content of the woods and pulps is undoubtedly the constant of most vital importance in the manufacture of paper. This value was therefore determined directly by the Cross and Bevan method, and the nature and progress of decomposition of the cellulose derived from sound and decayed material were studied. Data regarding the latter were obtained by determining the resistance toward chemical reagents, such as the’ copper number, and the percentages of a-,p-, and y-celluloses. The percentage of lignin or noncellulose materials is of importance in the manufacture of chemical pulp; therefore a knowledge of its rate of decomposition relative to that of cellulose would determine whether or not the organisms of decay produced a uniform degradation or selective action on woods and pulps. The comparison of the solubility in hot and cold water Qf the sound and decayed woods and pulps would be a direct measure of the losses sustained through the use of decayed 1 Presented before the Section of Cellulose Chemistry a t the 61st Meeting of the American Chemical Society, Rochester, N. Y., April 26-29, 1921. 2 It has been shown by Rose and Lisse that wood undergoes a chemical change during decay. THIS JOURNAL, 9 (1917), 284. 8 Ost and Wakening, Ckem.-Ztg., 461 (1910); Cross and /Bevan, “Researches on Cellulose,” I11 (1905-lo), 39. 4 Ordnance Department, U. S. A., PamPhlet 460 (1918), 16. 6 Cross and Bevan, “Paper Making.” 1916, 97; Schwalbe, “Chemie der Cellulose,” 1911, 637. 6 Schwalbe, Ibid., 625. 7 THIS JOURNAL, 9 (1917), 556.
materials. These constants would also indicate the extent of decav. as Rose and Lisse have nointed out that decav is associaied with increasing molecuiar simplicity. During decay wood breaks down to a considerable extent into substances which are almost entirely soluble in alkali.2 The solubility of the sound and decayed woods and pulps in strong (7.14 per cent NaQH) and weak (1 per cent NaOH) alkali would be a measure of the progress of decay and also show the hydrolytic action of the organisms of decay. This value would also tend to explain the results obtained in pulping decayed woods by the soda process. Since the reducing properties of wood and pulp are increased during decay, due partly to the increase in the percentage of the less stable or less resistant celluloses, uiz., @- and y-, and other substances, the copper number was determined. It also seemed desirable to show the relation between the ether-soluble content, the ash, the pentosan, and methylpentosan contents of sound and decayed woods and pulps. The moisture content was determined in order to make the calculations of all results for comparative purposes on the oven-dry (105’ C.) or moisture-free basis. Through the courtesy of a large number of mills cooperating with the Forest Products Laboratory, a number of shipments of sound and infected woods and pulps were received for chemical and pulping studies and for isolation of the typical organisms causing the decay. The woods studied were spruce, balsam, hemlock, and aspen, representing various stages of decay, determined microscopically. COMPARISON OF SOCSDAND IXFECTED SPRUCEWOODSAND PULPSDERIVEDFROM THEMBY MECHANICAL, SUL-
SODAPROCESSES The sample of fresh sound spruce wood used as a standard of comparison was obtained from the Marathon Paper Mills Co., Rothschild, Wis. The infected spruce woods, representing various stages of decay, as determined by the eye, were carefully selected from the following sources: FITE, AND
1-Very slightly infected, containing some mycelium (determined microscopically), from Cloquet, Minn. 2-Slightly infected, taken from the top of a pile of logs at the Marathon Paper Mills Co., Rothschild, Wis. 3-wood considerably more infected, taken from the bottom of a pile of logs a t the Marathon Paper Mills Co. 4-Very badly infected wood, such as would be rejected for pulping purposes, obtained from the Wausau Paper Mills Co., Brokaw, Wis.
Samples of these woods were shipped to the Forest Products Laboratory for chemical analysis and pulping trials, while some of the wood was made into mechanical pulps on experimental mill runs. The results of the pulping trials will be given in a later publication! I n order to establish the percentage of cellulose as a standard for comparison, and the relation of this constituent to 8 Otto Kress, C. J. Humphrey, C. A. Richards, M. Staidl, “Deterioration of Wood Pulp and Pulpwood.”
W. Bray,
and J. A.
