January, 1926
INDUSTRIAL A N D ENGINEERING CHEMISTRY
man then prepares a report on what he has found in the literature and on his proposal for experimentation. Following executive approval to this program of research, the experimental stage is entered, and regular reports and conferences are continued in it. The predominant feature of all scientific research is the extended use of recorded experience, which confers the power to predict the results of effort. Thus, the ceramist proceeds with assurance to determine the suitability of a new material in making refractories, because he possesses through bibliochretic study a knowledge concerning similar substances, requirements, and methods of test, by means of which he can plan his research with reasonable certainty of definite conclusion. The collection of recorded experience on any subject involves cornparison and critica1,analysis: it requires sound fundamental knowledge of the branch of science involved and of the systematic use of its literature (bibliochresis). I n order to progress in research, workers in pure and applied science should keep in line with psychological laws. The apprehension of a fact by the mind requires the exercise of the power of observation, and all research observations must be of a special character, minute, accurate, and selective. Observation means to see with attention, and as soon as concentration takes place a process of analysis begins, and the scientific investigator passes to classification and
101
generalization. The student of science, and particularly the graduate student who is being trained in research method, should therefore be taught to distinguish between the possession of information and the power or habit of thought. Thinking has no substitute. The first duty of an industrial fellow of this institute is to find out what his donor knows concerning the fellowship problem and what he has tried in its solution; because it is only by combining what the donor knows with what the fellow and the institute know and will learn that satisfactory progress can be made in solving the problem accepted for investigation. It is imperative that every industrial research man keep his mind open on every question until the evidence is all in and that he listen to the man who knows. He soon learns from experience not to ridicule new ideas and not to hesitate in asking his adviser or a laboratory co-worker to help him. To this end every one engaged in research should study himself and should know his own strong and weak points. Through success in research the scientist finds himself in possession of the ability to handle and control facts, the ability to discover new facts for himself. He finds that his knowledge has become power-power to move men and things. He is a t last on the highway toward an authoritative position, with its prestige, poise, peace, and freedom, the highest objects of professional life and education.
Tannin Content of Western Hemlock after Immersion in Sea Water' By H. L. Templeton and E. C. Sherrard FOREST PRODUCTS LABORATORY, MADISOX, WIS.
T
HE experimental work described in this paper was un-
dertaken in order to determine the effect of immersion in sea water on the tannin content of western hemlock bark. The question derives its significance from the practice of sending the unpeeled logs to the mill in rafts, numerous inquiries having been made as to whether the quality of the bark for tanning purposes is seriously rtffected thereby. The samples of bark were forwarded from the Olympic National Forest by the forest ranger. The tree from which the samples were taken was one hundred and sixty years old and about 51 cm. (20 inches) in diameter, growing at an altitude of 320 meters (1050 feet) and a t a distance of 9.4 km. (8 miles) from salt water. The bark was approximately 2 cm. (0.75 inch) thick. The first sample of bark was removed from the log before immersion in sea water and the others after periods of immersion amounting to 30, 60, and 90 days, respectively. The results failed to show any consistent relation between the length of immersion and the tannin content, as the bark which had not been in salt water showed a lower tannin content than the others, while that in salt water for 60 days had a much lower content than those that were immersed for 30 and for 90 days. The difference between the two latter samples was very slight. The results of the study indicate (a) that immersion in salt water for periods of 90 days or less has no observable effect upon the tannin content of western hemlock bark; (b)that the nontannins remain practically constant; (c) that the total and soluble solids are greater after immersion but do not greatly change with time; and (d) that the insolubles increase with time of immersion. I
Received August 28, 1925.
A study of the salt content of the bark before and after immersion failed to show any relation between the tannin content and the amount of salt present in the bark. Most of the salt was found in the outer layer of the bark. For purposes of record in this report and the appended tables the various samples of bark were numbered Series I (not in salt water) and Series 11, Series 111, and Series IV, which were in salt water 30, 60, and 90 days, respectively. A microscopical examination showed the presence of green Penicillium on Series IV. The amount of Penicillium found on the other samples apparently varied with the period of immersion, the sample that had not been in water being free of it while those exposed for different lengths of time had minute but visible quantities that apparently increased with time of exposure. The inside of the bark of Series I and Series I1 was a clear reddish orange, in I11 it mas darker, and in I V a dark red. After grinding, the last three series could not be distinguished from each other, but the first was of a lighter color. Determination of Tannin Content
Approximately 200 grams of bark selected from each piece of bark in each group were ground to pass a 20-mesh sieve. This amount was found to be insufficient if more than five determinations were required in which case a second grinding was necessary. Moisture content was usually determined on separate weighed portions, but as a check the moisture would sometimes be determined from an entire sample taken for analysis. The ground material was kept in Mason jars, the portions for analysis being taken out and
I X D USTRIAL d.VD E,VGINEERING CHEMISTRY
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Vol. 18, No. 1
weighed as rapidly as possible in the standard tannin de- marked. resulting in a thick sludge which had to be thortermination dishes which had been previously weighed and oughly shaken up before removal of samples. dried. Determination of Salt Content The apparatus employed for the determination of tannin content was that of Yocum, and the directions were those of From these results i t is evident that it is quite difficult the American Leather Chemists' Association (1919). The to obtain a series of determinations of tannin content that reagents, kaolin and hide powder, were prepared in the pre- show any significant trend with reference to time of immersion, scribed manner. The cold water outside extraction was per- and considerable variations must be expected. It was formed as follows: The cylinder containing the sample was therefore considered advisable to ascertain whether there placed on top of a 1-liter graduated cylinder. The bark was was any relation between the salt and the tannin content of thoroughly moistened and the cylinder filled t o the top of the the samples of bark. Bccordingly, the amount of chlorides tube through which the siphon tube passed. h short piece present was determined, and from this the amount of salt of rubber tubing with screw pinchcock was attached t o the present calculated. lower end of the siphon tube, and after the siphon was started Samples of the bark not used in the tannin determination the rate of flow was so adjusted by means of the pinchcock were carefully mixed in a crucible with sodium carbonate and that 500 cc. of cold water extract collected in 2 hours. The heated slowly until all the volatile organic matter had been extraction cylinder was then put in the extractor after re- removed. The heating was increased until the whole mass moving the rubber tubing, the water in the cylinder being was just molten; then the crucible was removed from the allowed to run into the boiler of the extractor. When all flame, allowed to cool, and the fusion dissolved in hot water. the liquid was out of the cylinder the sides were washed down The chlorides were determined gravimetrically as silver with the remaining portion of a liter of water, and the hot chloride. Five-gram samples were used in the first series of water extraction was started. determinations and 2-gram samples in the others. The reFrom this point the directions given by the American sults are shown in the third column of Table 11. Leather Chemists' Association are sufficient. The distribution of the salt in the bark was also investiA summary of the results of determinations of tannin con- gated. The outer portion of some of the pieces of bark tha tent is given in Table I. had been immersed in salt water for 30 to 90 days was removed and chloride determination made. It was impossible Table I-Tannin C o n t e n t of Western Hemlock Bark-Summary to study the 60-day immersion, as all the bark available had (Averages of all determinations) been used in the previous tannin determinations. The reTotal Soluble InsolNonsolids solids ubles tannins Tannins No. of sults are shown in the fourth column of Table 11. Series Per cent Per cent Per cent Per cent Per cent
detns.
Comparison of Tannin a n d Salt Contents
Air-Dru .. ~
I I1
21.82 25.29 23.83 27.49
19.04 23.03 20.35 23.58
2.79 2.26 3.47 3.91
I
23.01 26.84 25.36 29.02
20.07 24.45 21.66 24.89
2.94 2.39 3.70 4.13
I11 IV
7.82 7.84 8.20 8.06
11.22 15.18 12.16 15.52
6 8-6 6 5
8.24 8.37 8.67 8.51
11.82 16.16 12.99 16.38
6 8-6 6
Dry
I1 I11 IV
Table 11-Salt Series I I1 I11
IV
5
C o n t e n t of Western Hemlock Bark --PER CENT NACL-T In I n outer por- Tannins entire bark tion of bark Per cent 0.036 11.82 0.686 0.426 16 16 2.56 12.99 1.53 1.63 16.38
Days in salt water 0 30 60 90
The series of extractions varied noticeably in the amount of material that would settle out on standing. I n the first two series, although the extract was turbid, very little settled out; in the third a slight amount accumulated a t the bottom of the flask, while in the fourth the precipitation was very
The last column of Table I1 shows the results of the tannin determinations for comparison with the salt determinations. A study of the values shows that there is no consistent relation between the tannin content and the salt content, and for that reason the variations of the tannin content cannot be attributed to the presence or absence of salt. As regards the salt content itself, the period of immersion of the log in salt water and the physical condition of the bark must be held responsible for the irregularities shown. Since the salt was found to be distributed fairly uniformly throughout the bark, it may have a tendency through partial precipitation of soluble material to prevent the tannin from leaching readily while the log is in water. Such an a s s u m p tion might explain why the tannin content of bark immersed for 90 days had not greatly decreased. Actual tanning experiments would be necessary to determine the true tanning value of the liquors obtained by t h e extraction of these samples of western hemlock bark.
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