TS 1109 T4- Yrl 02394 UC-NRLF c 2 mi us i^B ! / * - &?. ' mmmmmmal a: ; ^^^^B ^ WM^m^Mmmmmmim^m^mimmmB - f ?,- '.< I PAPER TESTING METHODS Microscopical, Chemical^ and Physical Processes Described, with the Apparatus Employed By Committee on Paper Testing Technical Association of the Pulp and Paper Industry Price $3.00 Published by the Technical Association of the Pulp and Paper Industry 18 East 41st Street, New York City 1922 (Reprinted 1924) The following- list of books and pamphlets consists of works which should be on the desk or in the library of every paper mill executive. It includes the best works dealing with American practice, with a few of European origin that will be of general interest. HISTORY OF PAPER MANUFACTURING IN THE UNITED STATES, by Lyman Horace Weeks (1916). An account of the origin and development of paper manufac- ture in the United States from 1690 to 1916. ( Lockwood Trade Journal Co., 10 East 39th St.. New York. $6.) PULPWOOD AND WOOD PULP, by Royal S. Kellogg (1923). A short treatise on the basic raw material for paper with statistical data on production and consumption in North America. ( McGraw-Hill Book Co., 370 Seventh Ave.. New York, $4.) MANUFACTURE OF PULP AND PAPER, in five volumes, edited by J. N. Stephenson. Vols. I and II deal with the sciences in their relation to the manufacture of pulp and paper (1921). Vol. Ill, Preparation and Treatment of Wood Pulp (1922). Vol. IV. Preparation of rags and waste papers ; beat- ing, sizing and coloring; paper machines. Vol. V, in preparation (to be issued in 1924). Manufacture of paper and general mill equip- ment. (Technic .ciation of the Pulp and Paper Industry. IS East 41st St., York, $5 per vol. McGraw-Hill Book Co., publishers.) MODERN PULP AND PAPER MAKING, by G. S. Witham, Sr. (1920). A practical in treatise which gives particular every phase of papermaking from the saw mill to the finishing room. (Chemical cata- log Co.. 170 Metropolitan Tower. New York. $6.) A TEXT BOOK OF PAPERMAKING, by C. ': I. Bevan. Fifth edition, containing additional matter, and in part :th collaboration of |. F. Briggs. (Spon & Chamberlain. 120 Liberty St., New k, $9.) THE ACTION OF THE BEATER, by Dr. ml Smith (1923). An exhaustive treat- ment of the subject. Published by British Technical Section. (Distributed in U. S. by mical Association of the Pulp and Paper Industry. IS East 41st St., New York, $3.60.) THE RECOVERY AND MANUFACTURE OF WASTE PAPER, by James Strachan '18). This is a most useful and sup live work which can be recommended to all practical r>;i (Spon X- Chamber- lain, 120 Liberty St.. New York. $4.50.) THE TREATMENT OF PAPER FOR SPECIAL PURPOSES, by Louis Edgar Andes i 1'X)7). The processes of manufac- ture Toducts are out- lined in k of 23' It is ii' working manual, though it contains a collec- tion of formulas And furnishes for parchment and greaseproof papers, as well , as for a whole series of novelty papers. (D. Van Nostrand Co., 8 Warren St., New York, $3.) CHEMISTRY OF PULP AND PAPER MAKING, by Edwin Sutermeister (1920). A practical book for paper mill chemists, superintendents and students. It is based on notes and experiences of the author dur- ing a long term of service as chemist in the industry, a.-> well as study of the literature relating to the subject. It assumes a moder- ate knowledge of chemistry on the part of the reader. ( form Wiley & Sons, New York. $6.) CHEMISTRY OF PAPERMAKING, by Griffin and Little (1S94). This book has been out of print for some time. A photo- graphic reproduction of it was issued from Switzerland some time ago when a copy was procured from the Baker Company of Cleveland. Ohio. (G. E. Stechert & Co., 31 East 10th St., New York, $8.) TECHNICAL METHODS OF ANALYSIS, by Roger C. Griffin (1921). A good work for analytical chemists. (McGraw-Hill Book . 370 Seventh Ave., New York, $6.) THE PAPER MILL CHEMIST, by Henry Stevens (1907). (D. Van Nostrand Co., Warren St., New York, $4.) PAPER TESTING METHODS, by the Com- mittee on Paper Testing, TAPPI (revised 1922). A practical treatise on the analysis paper. (Technical Association of the Pulp and Paper Industry, IS East 41st St., New York, $3.) FROM PAPER MILL TO PRESSROOM, by William Bond Wheelwright (1920). (George Banta Publishing Co., Menasha, Wis., $2.) PHILLIPS' PAPER TRADE DIRECTORY OF THE WORLD, by S. Charles Phillips. Usued yearly. (S. Charles Phillips & Co., 47 Cannon St., E.C., London.) LOCKWOOD'S DIRECTORY OF THE PAPER AND ALLIED TRADES. Issued uially, in September. Contains a direc- tory of paper and pulp mills in United States and Canada, and classified lists of paper and mill products, besides addresses of paper i board merchants, twine manufacturers rind wall paper printers. There is also a ful reference list of watermarks and brand names. (Lockuood Trade Journal Co., 10 East 39th St., New York, $7.) PAPER TESTING METHODS Microscopical, Chemical, and Physical Processes Described with the Apparatus Employed By COMMITTEE ON PAPER TESTING ot the Technical Association of the Pulp and Paper Industry Published by the TECHNICAL ASSOCIATION OF THE PULP AND PAPER INDUSTRY 18 East 41st Street, New York City 1922 Copyright, 1922 by the Technical Association of the Pulp and Paper Industry New York CONTENTS Page LIST OF ILLUSTRATIONS 6 I. PAPER TESTING 7 1 . Purpose 7 2. Development 7 3. Group of Methods 7 4. Record Cards 7 5. Sampling , 7 6. Tolerances , 7 7. Test Sample 7 II. MISCROSCOPICAL EXAMINATION 7 1. Estimation of Fiber Content 7 a. Preparation of Slide 7 b. Discussion of Manipulation 10 f . Common Stains 11 HERZBEHG'S 11 JENK'S 11 SUTERMEISTER'S 12 d. Special Stains , 12 LOFTON-MERSITT SULPHATE STAIN 12 PHLOROGI.UCINOL 12 ANILINE SULPHATE 13 PARA-NITROANILINE 13 THE C. G. BRIGHT STAIN 13 2. Classification of Fibers Used in Papermaking .... 13 3. Degree of Beating -. 16 4. Specks or Dirt in Paper 16 5. Starch 16 III. PHYSICAL TESTING 17 1. Effect of Relative Humidity 17 a. Relative Humidity 17 b. Moisture 18 c. Weight 18 rf. Bursting Strength 18 e . Tearing Strength . . . 19 f. Folding Endurance 19 g. Breaking or Tensile Strength : : 19 2. Characteristics of Paper . '. 19 a. Machine Direction 19 b. Wire or Felt Side 19 3. Area of Sample 19 4. Weight of Sample 19 a. Balances and Scales : 20 />. Conversion Factors 20 SUBSTANCE NUMBER 20 METRIC FACTORS 20 ROLL LENGTHS 20 5. Bursting Strength 20 a. Description 20 b. Comparison 20 c. Ratio 20 6. Thickness 21 a. Description 21 b. Variations ...: 21 7. Bulk 21 S. Folding Endurance 21 a. Description .'.. 21 535789 CONTENTS Continued Page b. Calibration 22 r . Accuracy 23 9. Tensile or Breaking Strength 23 17. Description 23 b. Wet Tensile '. . . 24 r . Stress-strain 25 . Wet tensile test. 7. Stress-strain tesl for heavy bag paper, indicating stretch under load. X Additional melhods for absorption. 9. Tearing tesl : a brief discussion of live methods or apparatus. 10. Conductivity or electrolytic method for measuring the siz- ing quality of paper. 11. Volumetric composition of paper. 12. Method for measuring the number of conducting particles in thin paper. 13. Resistance to water penetration. 14. Sulphur in paper. 15. Tarnishing test. Throughout the report, wherever the author, inventor or origina- t'ir of a method or apparatus is known, reference is made and credit is given. Wherever data or information are taken directly from a publication, reference is made to the corresponding number < : thi j bibliography. In reference to the investigalion of microscopic examination of lilx-rs and the bursting strength of paper, as proposed by the com- mittee last year, it was not possible to include the results in this report. Data have been received from about half of the co-operating laboratories, but it is planned to complete the study and publish the results later. The indications are, however, that the various laboratories do not get as close check results as would be expected. It is believed that the Paper Testing Committee has arrived at a place where a change of policy is desirable. In the past, this com- mittee has suggested and proposed various methods of testing which, in its judgment, were of value in determining the quality of paper. It is thought desirable that TAPPI authorize this committee to investigate the following subjects with the view to putting paper testing on a more scientific basis. With the active co-operation of various laboratories equipped for paper testing, it is .believed that data can quickly be collected to permit of more (lelinite official methods of testing. 1. A survey be made of the various laboratories with a view to determining the extent of paper testing equipment available. 2. The development of standard official methods of the Associa- tion to be used by its members. 3. A study of the relation of the various physical tests of paper and an attempt made to reach positive conclusions. 4. A study of the proper meaning or interpretation of the various tests and an attempt to reduce the tests (chiefly physical) to M>me fundamental units. 5. The determination of the proper test for a particular use. In conclusion, it is thought that paper testing should be put on a firmer basis and that this Association is responsible to the paper industry for the development of methods of measuring the quality of the paper and it is hoped that this commitee will be permitted to follow the program suggested above. GEORGE R. ATKINSON, Scott Paper Company, Chester, Pa. FREDERICK A. CURTIS, Paper Section, Bureau of Standards, Washington, D. C. CHARLES A. POORNESS, Kimberly-Clark Co., Neenah, Wis. JOHN H. GRAFF, . Brown Company. Berlin, N. H. HELEN U. KIELY, American Writing Paper Co., Holyoke, Mass. EDWIN SUTERMEISTER, . S. D. Warren Company, Cumberland Mills, Me. SIDNEY D. WELLS, Forest Products Laboratory, Madison, Wis. FREDERICK C. CLARK, Chairman, Pejepscot Paper Company, Brunswick, Me. , -, J- , , - LIST OF ILLUSTRATIONS Figure Title Page 1. Chart of Paper Tests : 8 2. Test Record Card 9 3. Test Tube Shaker 10 *4. Binocular Miscroscope 10 5. Holder for Miscroscope Slide 12 6. Binocular Miscroscope 12 7. Classification of Fibers 13 8. Characteristics of Fibers 14-15 9. Photomicrograph Aspen 17 10. Balsam Fir 17 11. Chestnut 17 12. Hemlock 17 13. -Rag Pulp 18 14. Rice Straw 18 IS. Spruce Mechanical Pulp 18 16. Tulip Tree 18 17. Moisture Content of Paper 19 18. Quadrant Scale 20 19. Torsion Balance 20 20. Sheet Weighing Device 21 21. Pea and Beam Scale 21 22. Mullen Bursting Tester 22 23. Ashcroft Tester 22 24. Webb Tester 22 25. Thickness Tester 23 26. Bulk Tester , 23 27. Folding Tester 23 28. Calibrating Device 24 29. Green Folding Tester 24 30. Schopper Tensile Tester 24 31. Stress-Strain Tester 25 32. Perkins Tensile Tester 25 33. Absorption Test 26 34. Relation ibetween Filler and Blotting Quality 26 35. Opacity Apparatus 27 36. Witham Tearing Tester : . 27 37. Elmendorf Tearing Tester 28 38. Schopper Tearing Tester 28 39. Valley Size Tester 29 40. Sizing Test Apparatus 29 41. Glarimeter 30 42. Glarimeter Principle 30 43. Martins- Koenig Photometer 31 44. Conducting Particles 31 45. Rosin Kxtraction . 33 I'AI'ER TESTING METHODS PAPER TESTING METHODS Microscopical, Physical and Chemical Processes I. PAPER TESTING 1. Purpose Tlic testing of paper is performed for three reasons and it is possible that methods suitable for one purpose may not be suit- able for another. These purposes are: (a) to study the manu- facture in order to improve the quality, (b) to maintain a pre- determined quality, and (c) to determine whether the quality is equal to a predetermined standard or specification. The manufac-" ttirer is interested chiefly in (a) and (to), while the user or buyer is interested in (c), when paper is bought on specification. It is obvious that various methods may be developed for use in mills that are entirely satisfactory for the development of quality and lor maintaining that quality. It is thought, however, that the methods used by testing laboratories in connection with the pur- chase of paper on specifications, should be so defined and stand- ardised that comparable results will be obtained by different labor- atories. The methods herewith given are in some cases .merely tenta- tive suggestions which can not be accepted as standard without further investigation. It must be understood, however, that in de- termining what tests to make, that the purpose for which the paper is to be used is of primary importance, and that that test should K used which will indicate the quality that is specifically desired. 2. Development I'aper testing has developed rather slowly in this country and many of the methods are of foreign extraction, as are some of the instruments and apparatus. However, a considerable amount of development has_ taken place, and there are a greater number of methods now available. This development has not, however, been in any systematic manner and has been spread over the whole field of testing, to meet special conditions. A systematic study should be made and standard methods developed and used. 3. Groups of Methods For convenience, the various methods of testing are grouped into three classes: microscopical, physical and chemical. In most cases, some of the methods from each class are necessary. The accompanying chart ( P'ig. 1 ) indicates some of the tests given and shows the relation between them. It is obvious that all the tests indicated are not necessary in any one particular case but such tests should be used that will indicate the quality of paper necessary for a particular purpose. 4. Record Cards Complete laboratory records should -be kept of all tests (especially original data) and in such a manner as to be always available. The accompanying 5 by 8 in. record with both sides reproduced is offered as a suggestion. (Fig. 2) though individual requirements may necessitate certain alterations. 5. Sampling The proper sampling of paper for test or the interpretation of the test data in connection with sampling has been neglected. It is pointed out, however, that no test data is more accurate than the sampling. This applies with especial force in connection with the testing of a shipment of paper to determine whether it con- forms to a definite specification. It is oSvious that cases, bundles. frames, rolls, etc., must be sampled differently but as much care should be exercised in this connection as in the sampling of wood gulp_for moisture. 6. Tolerances The va'.ue of the test data is accurate only when a large number of tests are made or when proper tolerance is allowed for. This tolerance is necessary, owing to the errors which are inherent in the whole process of paper testing. The errors are introduced (a) 'by improper or incomplete sampling, (b) by the natural lack of uni- formity in paper, due to its structure, and (c) by the error of the: apparatus or method of testing which may either be inherent in the apparatus or due to improper manipulation. 7. Test Sample The original sample, obtained by .proper sampling, should be suf- ficiently large and of enough sheets to enable all the proposed tests to be made without recourse to an additional sample. The various tests should lie made on the several sheets of the sample in order to obtain a reasonably fair average. II. MICROSCOPICAL EXAMINATION 1. Estimation of Fiber Content a. f'n-farutiiiii of Slide. Secure a representative sample by clipping a piece of about the area of a cent from the corners of several of the sheets to be tested. Place the samples in a dish. small beaker, or test tube, cover with a 0.5 per cent caustic soda solution and bring to a boil to remove sizing or other binding material. The pieces are next drained, washed several times in tap water, rolled into a small pill or ball between the thumb and first finger for about 1 min.. then placed in a test tul>e, about half filled with water and shaken vigorously, so as to defiber thoroughly the particles of paper. A small part of this deftbered mass is removed from the test, tube by the aid of a microscopic needle (Note 1) thoroughly dried on absorbent paper (Note 2) that is free from lint, placed on a microscopic slide and covered with several drops of Herzberg's stain. The fibers are carefully pulled apart, by the aid of microscopic needles, so that they 'will not lie too much in a bunch and are then covered with the cover glass. (Note 3.) The slide is now ready for an estimation by the aid of the microscope. It is suggested that after the small sample of paper has been boiled with 0.5 per cent caustic soda, that the sample be next washed with 0.5 per cent hydrochloric acid and finally with water. It is difficult to wash all the caustic from the fibers and an addition of hydrochloric acid seems advisable. ee First method. Use a lest tube of about ^-in. diameter and about 6 in long keep the fibers diluted with water, FO that they will mix readily when shaken vigorously. The fibers mix very easily if the test tube is about two-thirds full ]? at "J"yj 5 b - ers ' The micros< :P'c needle referred to is a pointed steel needle imbedded in a small wood or metal handle. Shake test tube and then quickly incline it at a sharp angle. Insert the point of the microscopic needle and remove a small bundle of fibers for use in making up the microscopic slide. The foregoing method of procedure is best where the fibers are long, such as in a rag bond, ledger, or writing paper, also for long-fibered wood papers made of new s'llphite cc sulphate pulps. For groundwood papers or where the fibers are very sh.,it anil contain a large quantity of fine broken particles such as Cooked old iraper stock, the use of the needle to secure a representative sample will result in securing more long fibers than short fibers with a result of inaccuracy. For papers containing much short fine fiber it is . l>est to use the second methid. PAPER TESTING METHODS \ E -. -.; :. .- ~C ^"ZI ~1 Contftroft k/ood r~>btr \- -| BrooJL ro/M//7^^]_ - \_Grouad l or MfckarrKO/Jktx,^ ftyaV- ~l ffani//g or Jufii -\ 'Sfratv H*m/ac** RrtfS BrecJi Hfmbcfa Fir* -\ <7Mf/- rt^eSAfr fibrous rnafirfa/f \ Com/tfion ofbeafrno \ foreign T&fe/** -Q Thichifts~\- Sffvrstlny StrtnytQ - -{An* -< ^foUtny no/iS6f*v('"'Oe*t*?aefic* S'X* \_ T Ttailtr of7lir/f L <,/ 7t^//A tKVfS/XI' a*" ^yw^>* C 7S/0 /or / Grays. . AtoS^ /e* WwW* FIG. 1. CHART OF PAPER TESTS PAPER TESTING METHODS Serial No. ?a/iy o/ Amer/ca. Received 3-/S-ZZ Folder No. 33(333 Reported 3-ZZ-2Z MARKED (/stseast7/xe.(> /oS 558 .. .4.Q.. 4* .6.9.. .3.8.. 99 . 39... 40 ..7h .AS. .Jk& 3 ....4if..... ...43..... ....43.... .6.4... ..76,... ..73... ./o-At.. ./ft*. 60 4.Z ._&*>__ 6.87 *8 63* NO. ABSORPTION IN 10 MINUTES Klemm Method Machine Direction Cross Direction Breaking strength in Ibs. per 1" width-tBreaking strength in kg per 15 mm width)x(3.73). Breaking length in yards=< Breaking strength inlbs. per 1" width)x(13,889)+(Wt in Ibs. per 25X<0, 500). Wt., in Ibs., el ream oI5()Osheets-(Wt. of 1 sheet in grams)x(U02) Wt. in grams per sq. meter=(Wt. in Ibs. per 25X40, 500) x (1.406). Wt. in grams per sq. meter (Wt. in Ibs. of any ream o'500sheets)X(140G.13)-f-(Area of sheet in sq. in.). Wt. of any 500-sheet ream (Wt. in grains per sq. meter. X(Area ol sheet in sq. in.)+(140c has one end rounded so as not to have sharp edges and the other end is p: ovided with a small rubber bulb. This serves as a dropper. Spence and Kranss describe the modus operandi as follows: "When ready to prepare the slides, the test tube is well shaken, the dropper inserted, with as little delay as possible, two inches below the surface, two bubbles of air expelled and a little less than half an inch of the mixture drawn into the tube. This is trans- ferred to slides, completely emptying the dropping tube, which will make four drops. The slides are placed in an air bath to expel moisture, cooled, and each drop stained with Herzberg stain, just before it is to be examined. The excess stain is then removed after the colors have developed to a maximum point, about 3 min. required by tilting the slide and the cover glass placed over the spot." After the cover glass is in place, it should be pressed down gently to expel excess stain and any excess stairj removed by absorbing it with a piece of blotting or filter paper. Note 2 The absorbent paper used should have a hard, smooth surface so that no lint will adhere to the sample of fibers. As soon as the sample is dry it may be removed to the miscroscopic slide and is then ready for the drop of stain. A second method of drying the sample is to put it on the microscope slide and then touch it with the corner of a piece of folded filter paper of ordinary quality. For this purpose; a cheap grade of filter paper may be cut into pieces about 1 J4 by 4 inches. This makes a handy size for use in drying the sample and also in removing the excess stain frrm around the edges of the eter. The round or square cover glasses are necessary for high magnification and have one disadvantage in that they are very fragile. The third type of cover glass is the same size as the microscope slide, and if thin microscope slides are used then a second microscope slide may be used as the cover for the first. The chief advantage of the large cover glass is that it permits three or four fields to be made up one each slide. FIG. 3. TEST TUBE SHAKER BY M. B. SHAW, BUREAU OF STANDARDS cover glass. Care must always be exercised to prevent the sample uf fibers to be tested from becoming contaminated with fibers from the absorlient paper or filter paper. A third method of drying the sample of fibers is to place them on a microscope slide and evaporate the moisture in a current of heated air, in an oven or by some other suitable arrangement. In regard to drying the small sample of the fibers on the microscope slide, attention is called to the fact that the sample must be dried so that the stain will not be diluted and yet must not be dried too hard because then it is difficult to separate the fibers and the staining does not take place uniformly. Note 3 There are three kinds of cover glasses. The first two are very thin pieces of glass either round or square of approximately half an inch in diam- b. Discussion of Manipulation. T\\e following suggestions are offered to those just beginning these tests: It is absolutely essential to 'have a satisfactory stain or else the Fir,. 4. BiNccur.AR MICROSCOPE results will be worthless. To test out a stain make up a mixture of about equal parts of bleached soda pulp, bleached sulphite pulp and rag filter paper. Prepare a microscope slide from this mixture and stain with the stain to be tested. If the stain is correct, then the soda pulp should show a dark blue color, due to the thicker and more opaque fiber walls, the sulphite pulp should show a //.tr/i/ />/!. due to the thin filler walls and the rag fibers will show a red or tame-red color. If the blue color is more of a violet, then too much iodine is present and more water or xinc chloride should be added. Zinc chloride produces 'the 'blue color, iodine produces the red and the yellow colors and the addition of water serves to weaken the color that predominates. In some cases where it is necessary to examine all grades of paper, it is advisable to keep several stains on hand. A stain that gives the best color on groundwood and bleached sulphite seldom gives a correct color on mixtures of rag, bleached sulphite and soda pulps. In such a case, make up one stain so that it will give a bright Iciinni yellow on a known sample of groundwood pulp and a slightly greenish blue on unbleached sulphite. For the mixture of rag, bleached sulphite and soda pulp, so adjust a second stain that the rag shows as a clear trine-red, the sulphite as a blue and the soda fibers as a dark- blue. In testing out a stain always have on hand authentic samples of pulp so these mixtures may be made up. To check estimates of fiber analysis, slides of fibers in known proportions are made. Pure stock is l>eaten in a small ibeater and made into hand sheets. Sheets of the various pure fibers are kept under the same atmospheric conditions. To make up a field of known composition take weights of the pure fiber sheets and make up a total of at least 5 g. in proportions to give the percentage desired. Disintegrate and mix thoroughly by shak- ing with shot in a bottle or by the action of a small disintegrator. PAPER TESTING METHODS 11 Sample and make up the slide as for any disintegrated paper sample. The estimation of the fiber content is based on the relative pro- portion of the kinds of fibers contained therein, expressed on the percentage 'basis, considering the total fiber content as 100 per cent. In making a fiber estimation no account is taken of the per cent of clay, alum, size, etc., that may be contained in the paper. It is always advisable to make up at least two separate samples of fiber taken from the test tube and the final result should ! be the means of all observations on these two separate slides. In special cases it may be necessary to make up four separate fields. 'There are two methods of making the determination for fiber con- tent. One is the count method, the other is the estimation method. Both methods have their advocates and both give good results. This committee, however, recommends the estimation method, be- lieving it to have the following advantages : (1) It is more accurate under certain conditions, namely, in making groundwood determinations, and of equal accuracy under all other conditions; (2) it is much quicker; (3) it is easier to teach an individual to estimate correctly than to count correctly; (4) it is possible to make up standard mixtures for ready com- parison. The estimation method involves training the eye by the com- parison of unknown samples with standard mixtures of known composition. The result of each observation on each part of a field examined, should be written down and the mean of. all the observations is the result to be reported as final. Accuracy in the estimation method involves practice and continual reference to known standards. Unstained slides of these standard mixtures should be kept handy to be made up in case there is any doubt a : bout the sample being tested. There is a third method for fiber determination that has been proposed by Spence and Krauss *(37) which is worthy of descrip- tion here and recommendation to the Technical Association. This is known as the fiber-weight-length method. The procedure is as follows: Samples are made up as described under Note 1, second method. The slide is placed under a microscope of 160 diameters and the lengths of the various fibers are measured in terms of the diameter of the field seen through the microscope. An adjustable stage is also essential as otherwise it would not be possible to move systematically over the entire sample to be examined. After four samples have been estimated as above described, the figures are added together to get the total length of each kind of fiber present. The total length of each kind of fiber present multiplied each by its own weight factor gives a set of results that are directly com- parable and may "be converted into the per cent of each kind of fiber present. The weight factors as determined 'by Spence and Krauss are as follows: Rag, 1.000; hemlock pulp, 0.870; poplar pulp. 0.454; birch pulp, 0.6S2; beech pulp, 0.525 ; maple, 0.365. This method, which is undoubtedly a step in the right direction, is recommended as a method to be used in cases of dispute 'between two different analyses. It is a very slow method and cannot there- fore be used where many routine samples must be examined each day. The Spence-Krauss method is undoubtedly the only method that will enable a determination of the proportion of the various kinds of wood present, such as a mixture of hemlock, beech, poplar, birch, maple, etc. In any method of testing it is always advisable to make use No definite recommendation is given in regard to the microscope magnifica- tion. This must be left to the individual preference. Satisfactory estimations may be made with a magnification as low as 45 diameters and equally satis- factory work is being done with magnifications as high as 120. The lower magnification has the advantage of giving larger fields, whereas the higher magnification gives more of the detail of the markings of a fiber. The mo- nocular and binccular microscopes both have their advocates, and like the mag- nifying power, it is very largely a matter of getting used to a certain procedure. Where only one microscope can be purchased it is better to use a monocular, as it can be fitted with more attachments to suit special needs. It may be well to add that a low power of about 25 diameters for examining specks and sur- faces, also a high ]>ower of 350 or 400 for details of fiber markings will often be found to be of use. Spence and Krauss*(37) recommend a magnification of 160 diameters. of all possible apparatus that may be of assistance in carrying out the method described. There are no holders for microscope slides on the market, therefore a brief description will be given and it may be constructed at almost no expense for labor or material. The holder for the microscope slides is made as follows : Take two pieces of brass 34- in. thick by y^ in. wide by 3 in. long (oak or maple may be used if the brass is not obtainable), then cut a groove }^ in. wide by V& in. deep along one of the longitudinal edges of the brass strip. This groove then serves as a rest for the glass slides. The pins (see Fig.. 5) serve to prevent the glass slide from slip- ping out of the grooves while the bundles of fibers are being teased apart. Also note the parts on the sketch marked "Painted black" and '"White surface." These serve as a background. The glass slide is placed over the black 'background when the unstained fibers are first put on the glass slide, as the light (almost white) colored fibers show up best with a black background. After the Herzberg stain is added, the glass slide is pushed to the other end of the brass holder, which brings it over the white background and causes the dark-stained fibers to show up more distinctly and enables even the smallest bundles to be separated. For best results for microscopic work, a clear north light is de- sirable, and is to be preferred. However, where there is a large amount of routine testing that must be done, it is more advisable to have a more constant source of light. There are various types of lamps available but good results can be obtained with a Mazda nitrogen-filled lamp of 150 watts. It is necessary, however, to use a blue "daylight" filter in that cas'e. It is to be noted that the color of the stained fibers on the slide will be somewhat different for the two kinds of illumination. c. Common Stains. HERZBERG'S. *(10). The Herzberg stain is made according to the following formula : Solution A 2O g. zinc chloride. 10 cc. of water (preferably distilled). Solution B 2.1 g. potassium iodide. 0.1 g. iodine crystals. 5.0 cc. of water (preferably distilled). Dissolve solutions A and B separately, then mix and allow to stand several hours, or until all sediment has settled out. The clear liquid is next decanted and is ready to 'be used in staining the fibers. All iodine solutions must be kept in the dark, as otherwise they deteriorate rapidly. The Herzberg stain is a selective stain, that is, it has selective staining properties. Ground or mechanical wood pulp, jute, flax tow, uncooked manila hemp and in fact most every vegetable fibrous material containing large quantities of ligno- cellulose, is colored yellow or lemon yellow. The removal of their lignocellulose content changes the staining effect from a yellow to a blue or. wine-red color, though jute and a few other fibers remain unchanged in color. Thoroughly cooked and bleached soda and sulphite pulps, cooked and bleached straw pulp and esparto are colored blue or navy blue. 'Cotton and linen rags, thoroughly cooked and bleached manila hemp, and certain of the Japanese fibers are colored a wine red. In connection with the Herziberg stain, the following alternative formula is suggested: 25 cc. zinc chloride solution (saturated) at 70 F. ; 5.25 g. potassium iodide; 0.25 g. of iodine, and 12.5 cc. water. Owing to the difficulty of obtaining zinc chloride of uniform moisture content, it has 'been found more satisfactory to use a saturated zinc chloride solution. By mixing the ingredients as stated above, the proper stain can 'be obtained at once. JENK'S. The stain known as "Jenk's Stain" is of value when it is desired to ascertain definitely small amounts of rag fiber with only a poor Herzberg stain available : To 50 cc. of saturated magnesium chloride solution add 2 l / 2 cc. of iodine potassium iodide 12 PAPER TESTING METHODS solution made up as follows: Potassium iodide, 2 g. ; iodine, 1:15 g., and water, 20 cc. Use exact quantities and keep solutions from the light; the stain is kept best in a small brown bottle with a pipette. Rag fiber is stained brown, straw is stained blue-violet, groundwood is stained yellow, and chemical wood either no color or deep red. SUTERMEISTER'S. *(3). A stain which is considered by some to be better than the Herrberg stain is made up as follows : Solution A. 1.3 g. iodine and 1.8 g. potassium iodide in 100 cc. of water. Solution B. A clear, practically saturated solution of calcium chloride. In using this stain apply a drop or two of Solution A to the moist fibers on the microscope slide. After a minute or so remove the stain by means of a blotter and immediately put on a drop or two of Solution B. Pull the fibers apart and distribute them by means of needles as 'before and drop on a cover class or thin miscroscope slide. Any excess of Solution B should 'be removed by absorbing it with moist blotting paper. This stain is also selective in its action, the colors produced being as follows : Red or brownish red : cotton, linen, hemp, ramie. Dark blue: bleached soda pulps from deciduous woods. Bluish or reddish violet : bleached sulphite fibers and the thor- oughly cooked part of the unbleached sulphite. Greenish : jute, manila and the more lignified fibers in unbleached sulphite. Yellow, groundwood. As with the Herzberg stain this one should be adjusted by trial on known mixtures of fiber until it shows satisfactory difference in color. The two solutions should be protected against evaporation s FIG. 5. HOLDER FOR MICROSCOPE SLIDE. and dust but light does not change their staining properties to any extent. d. Special Stains. There are many stains in use for special purposes and a descrip- tion of them is therefore advisable. LOFTON-MERRITT SULPHATE STAIN. *(99). The stain which was found to be most satisfactory in differentiating between unbleached sulphite and sulphate pulps or fibers was a mixture of one part of a 2 per cent aqueous solution of malachite green and two parts of a 1 per cent aqueous solution of basic fuchsine, or magenta. The solutions were made up according to the following formulas, kept in tightly stoppered separate bottles, and mixed only when wanted for use: A Malachite green 2 g. Distilled water 100 cc . B Basic f uchsina 1 g. Distilled water 1 00 cc . Since there is considerable variation in the quality of dyes from various sources, it is not to be expected that any given combination of dyes or method of procedure will best fit all cases ; it is, indeed, more than probable that the compound stain will have to be modified somewhat as to its two components, depending on the source of the dyes. FIG. 6. BINOCULAR MICROSCOPE After this stain, therefore, has been made up according to formula, it will be necessary to test it out on samples of sulphite and sulphate fibers. To do this, samples of unbleached sulphite and sulphate pulps should be prepared and a few fibers of each placed on a slide, care being taken not to get the two samples mixed. The fibers are then dried and stained, as directed below, and then examined under the microscope. All the sulphate fibers should have a blue or Wm--.^''<'<'/i color, and all the sulphite fibers sin mid have a (>urple or laicndcr color. If any purple fillers appear in the sulphate pulp this indicates that too much fuchsine is present in the combination, and a little more malachite green solution must be idded to counteract this effect. If, on the other hand, some of the sulphite fibers show green or blue, there is too much malachite i;reen in the combination, and more fuchsine solution must be added. Of course the analyst must be sure that he is using authentic samples of the two pulps for this test. When tested out in this manner and the proper combination found, the stair is ready to be used on unknown combinations of fibers containing either unbleached sulphite or sulphate, or 'both. A mixture of one-half sulphite and one-half sulphate may also be used to test out the stain, the proper combination for the stain being indicated when one-half of the fibers are colored blue, and the other half purple. The stain should not be used for more than a few hours after being compounded and should be made up anew at least each day. PHLOROGLUCINOL. Dissolve 5 g. of phloroglucinol in a mixture of 125 cc. of distilled water and 125 cc. of concentrated hydro- chloric acid. The solution should be kept in the dark as much as possible as it is prone to lose its staining property on exposure to light. This solution produces a inagrnla or wine-red color on PAPER TESTING METHODS 13 mechanical pulp. The color may easily be noted by applying some of the stain to a piece of news print paper. There is approximately 80 per cent of mechanical pulp in newspaper so that a deep magenta color is developed. The depth of color is an indication of the amount of mechanical ' pulp present. A very light shade of color, however, does not necessarily prove the presence of mechanical pulp, as partly cooked jute, partly cooked unbleached sulphite pulp, and some other fibers are also slightly colored. An additional formula is as follows : Phloroglucine 2 g. Alcohol (95%) 100 cc. Cone. HC1 50 cc. ANILINE SULPHATE. Dissolve 5 g. of aniline sulphate in 50 cc. of distilled water and acidulate with one drop of concentrated sulphuric acid. This stain produces a yeltov. 1 color on papers con- taining a large percentage of mechanical pulp. This stain is not quite as sensitive to mechanical pulp as phloroglucinol, but it is easier to obtain and prepare. PARA-NITRCANJLINK. Saturated solution in concentrated hydro- chloric acid. This stain produces an orange yellow color in the presence of mechanical pulp and other lignified fibers. .THE C. G. BRIGHT STAIN. *(78). This is used for distinguish- ing between bleached and unbleached pulps. Solution A: Ferric chloride solution (n/10 normal) equal to 2.7 g. FeCl 3 6H 2 O per 100 cc. distilled water. Solution B: Potassium ferricyanide solution (n/10 normal) equal to 3.29 g. K 3 Fe (CN) per 100 cc. distilled water. Solutions A and B should each be filtered through a fresh filter into clear glass stoppered bottles. Equal volumes are mixed fresh whenever the reagent is used. Solution C: Substantive red o.4 g. of benzopurpurin 4B extra (Bayer Co.), 0.1 g. of oxamine brilliant red BX (Badische Co.) and 100 cc. of dis- tilled water. Have water hot and stir in the dyes slowly. The staining solutions are used in tall narrow cylindrical beakers which are set into a water 'bath. The slides are suspended in the beaker by a clamp which holds them at their upper ends, the clamps resting across the top of the beakers. The bath is heated by a small bunsen burner with a pilot flame, so that when the re- quired temperature is reached the "pilot flame may be used to main- tain the temperature at the required amount. A thermometer should be suspended in the stain and the beaker containing the stain should lie as small as possible so as not to use too much stain at one time. In making up the slides for this staining method it will be necessary to use the dropper method as used by Bright and also by Spence. (See methods of making up microscope slides as out- lined on page 7.) This dropper method involves dropping a dilute mixture of water and fibers upon the slide and then evaporating the water. The dry slide is then ready for staining. Method of using solutions A and B known as the potassium ferric ferricyanide stain. Mix equal volumes of solutions A and B, heat to 35 C. in the water bath, regulating the pilot flame so that the temperature will remain constant within 1 for a period not less than 15 min. The dry slide is then dipped in distilled water to moisten it uniformly, so that air bubbles will not be formed when it is immersed in the stain. If air bubbles are formed the fibers under the bubbles will not be stained. If dipping in water still leaves bubbles, they can be removed by blowing across the slide from the edge. The slide is then suspended in the stain and left there for 15 min. at 35" C. It is then removed and washed, by dipping in and out of a beaker of distilled water six times and repeating the process in a fresh beaker of water. The slide can then be placed wet into the red solution, but it is perhaps better to dry it out so that the fibers will be stuck on tightly again in case they have been loosened to any extent by the treatment. Method of using solution C, the substantive red stain; A fresh solution is heated to 45 C., and the -slide, after moistening and excluding bubbles as before, is suspended in the solution for five minutes at 45" C. and immediately washed in two beakers of dis- tilled water. The slide is then dried and a cover glass placed on with a drop of balsam. Directions for assuring best results : To get the clearest, bright- est results, distilled water must be used throughout, and the stain- ing solutions must be fresh. The two solutions for making ferric ferricyanide will keep well if placed in separate 'bottles. Equal volumes are mixed together immediately before using. The red solution should be freshly made each time for the best results, as it gets thick and stringy on standing, especially when it is being _he_ated up continually. Staining under the conditions described gives an unbleached sul- phite perhaps the deepest blue it is possible to obtain without depositing blue on the slide and on the bleached sulphite; the method also produces the best red on the bleached fibers without turning the unbleached fibers purple. Unbleached sulphite from different mills varies considerably in lignin content, hence some samples stain a deeper blue than others. The foregoing condi- tions give a satisfactory blue on a sample of high grade im- ported unbleached pulp as well as a better color on the average run of unbleached pulps, the latter being not so well cooked as a rule. With pulp containing more lignin it is possible to use a slightly stronger treatment with the red and thus get a better color on the bleached without affecting the unbleached. After one has had a little experience with the method he can tell by the color of the unbleached fiber whether he may safely continue the staining with the red for six or possibly seven minutes at 45 C. At first, however, it is better to follow the directions as given. It is of prime importance to wash out or neutralize every trace of alkali in the fibers, as the blue is decolorized by alkali. This method of staining will in general give a distinction be- tween pure cellulose fibers and those which contain lignin. Rags, bleached sulphite, soda pulp or any thoroughly bleached material are stained red while unbleached sulphite, mechanical pulp, jute, or any lignified materials are stained blue. The principal application lies in the estimation of unbleached pulp in book papers. A con- siderable saving can be made by using unbleached sulphite instead of bleached, hence.it is important to know how much unbleached pulp there is in a sheet. 2. Classification of Fibers Used in Papermaking* (143) For convenience in studying filters, it is desirable to know the relations of the various groups and the accompanying charts (Fig. 8) indicate the arrangement of the fibers that are used for papermaking. It is to be understood that this is not a 'botanical classification and the standard text book on botany is to be con- sulted if this information is desired. CLASSIFICATION OF FIBERS *(141) A suggested grouping of various fibers used for paper-making. A Seed hair fiber ( "? n ( Bombax wool East Indies B Stem fiber (bast family) C Leaf fiber. Flax or linen Hemp (cool temperate climate) Jute f Common nettle Nettle fibers, i China grass [ Ramie (water-resist! Sunn (India) Straw and esparto New Zealand hemp Abaca Sisal or Henequin (Yucatan) Aloe (South America) Piteira Pineapple leaf fiber ing) PAPER TESTING METHODS a _- 13 " 8 [A 1 t I B H C E 10 ^r s rt rt rt S " u E i s rH o E a "^ SJ! fl in a _ & f m o (A rt rt c 2 1 U s * bo n i I In "rt jn O ^ ^ ' E I B 11 II t_ re Is ^. . rt rt KJ rt . T) 13 k >~ = u . u n B ** 2 X rt X! t* o c; B " tfl BM ngitudi no ridge marks u e o c O z tfi 5 ~\ x. .0025" to average . 1 a S Slightly : B "2 '1 E rt u. 9 2 - c , M fi s > n o ^ **- .c 3 C ; 1 = o 5 o o SJ; S! U OJ in || "2 o - : ' -r ^ 4* .* 2 t> - J^ 1 'Jj o. si II PS H ' |j 3 i "3 2 t- c y. t; O H || Is & g "o C3 1> ^ ^ rt Flax (Lin urn us tissimutn) Cylindrical i JB X L ^4* Very narrcw |. "1 w 4J *| y c X U C o sx i = H - 1J S *- B is .j = u U rt CM s CM* il o 1 1 c V 1 I- t- o 0^> if O o^ cS 85*5 _ .- . t o 0) Si c o J3 p g V x&l | 5 II (f3 rt T3-O | I u JD U 1 S J S '* '^ C*6 A 2 p rt S il o B fi n fi V U V 4 - ba re"n ~ r: ^* u C c tflt/1 c o o U 1 Jl H 11 "1 C-U! 1 c ^o C o u 1 its e 1 ii S *o u O "o u "o .2 .- c C 3 u en S K 1 8 |^ "w o B a k- H "rt M u _o - J E K rt 1 3 - g 3 . 9 M tj 1 1 1 * u 1 u ^ 0= fi c J T3 u c 3 o. 1 re - oi -; * HI * r^. x ' * o 2 rsi ^j PAPER TESTING METHODS 15 * | u i "^ (fl c 1 '" V- o rt ITS o |E *c S'S x rt OJ > s* rt ^;-g || 1 i;| s||'S 1 I ll EH IB m" 11-s -=*- c tnOW u x*' 3 rt *- w o S o *o U s S **" V 1 I O y t C a a 3 CT) .2 c la's t o .C U i 3 _ __ o "S o'j *** o % * V li Coniferous ' ll 11 rt e jfj 1 Markings le in well bo Occasionally 3 Colorless Colorless o ll X h D o c a ll -c c ^ *S s ^ c o 3 rt " 1 _c _fj rt o 01 x "~ c S *o H = c 3 f * HI li II c IE sl s o - 5 8 o I H o a ' 1 5 A * Pi 3 1 i i S XiSi V a c u T; B SJ a o > '-6 f i > s " u .0 'c ^2 |i 3 fl) C c rt g O o -ll o c 5 " o o s O _0 c ll Regular i Thicker t c l- 111 ,1- J=*- i. U C ^x I! CC/J O -< t o i a. u h Reddish 1 e "o3 E rt.o 0) u 1 E c rt -c V H 2 M 2 t i U3 ?s ** ^ k- V > > c 1 11 5 gl is. rt t " J H ^ t t 3 ^ ^._' T - rt i o o ~fc ii rt ^ 13 JD q E tn PQ Ramie ( nettle til; /('/((/(-IJ.u'l rt 3 '2 P 3 o (/I _O O Ctf ^ OJ III u ^ I* 16 PAPER TESTING METHODS D Fruit fiber Cocoanut fiber E Wood fiber . Resinous or coniferous Non-resinous or broad- leaf FIG. 7 Larch-Tamarack Fir Spruce Cedar Pine Hemlock Cypress Birch Mulberry Beech Gum Tulip tree [_ Poplaf 3. Degree of Beating By a careful examination of the fibers under the miscroscope, it is often possible to determine something of the amount of 'beat- ing to which the stock has 'been subjected. The length of the fibers, the amount that the ends have been frayed and the degree of the breaking down of the cell-walls all give information in regard to the 'beating treatment. It is necessary, however, to have con- siderable experience 'before the results are reliable. The use of photomicrographs assists in this study and the accompanying plates indicate some of the characteristic differences of fibers and in beat- ing treatment. 4. Specks or Dirt in Paper The appearance of a sheet may show imperfections caused by foreign materials or malformation on the wire. These are the most common causes of poor-looking paper. Generally, specks need microscopic examination. A Bausch and Lomb binocular miscroscope shown in Fig. 6 and a set of dis- secting needles are useful. For chemical tests on small particles small test tubes made by sealing one end of small glass tubing are convenient if the reaction is to be watched under the micro- scope. Rubber. This is very objectionable. It finds its way into the stock along with rag stock, sometimes as rubber paste in tire fabrics and the like, and sometimes in paper stock as rubber bands from office waste. Under the magnifying glass rubber specks can be stretched by pinning down one end with a dissecting needle and pulling out the speck with another needle point. Rubber specks will give a characteristic rubber odor if burned by sticking into a flame on the end of a needle. They are soluble in carbon tetrachloride. Rosin specks. These are translucent amber-colored specks so re- sembling rosin that they are easily recognized. Proof of their iden- tity can be had by dissolving the separated speck in ether in a small tube so that the action can be watched under the microscope. Qualitative rosin tests can be applied to the speck as given under qualitative tests for rosin. Other specks resembling small bark particles may come from size which was made from impure rosin without proper filtration. Although not as translucent as the ordinary rosin speck they usually carry enough rosin to respond to the qualitative test. Wood specks. Chips or wood fibers which might result from the accidental grinding off of a beater paddle or similar cause can be quickly identified by applying phloroglucinol ; they give a char- acteristic red coloration as in the groundwood test. Iron specks. Washer or 'beater bars, jordans, scaly pipes, cor- roded overhead ironwork, and iron buttons from rags contribute iron in ; metallic or oxidized form at times. The metallic particles will be! attracted by a magnet after being freed from the sheet. The scale or oxidized iron can be dissolved in concentrated hydro- chloric acid and a drop of potassium sulphocyanate added. Iron gives a characteristic wine-red color. This test can be applied to the separated particle in a small tube, or the sheet suspected to contain iron may be placed on a glass plate, wetted with concen- trated hydrochloric acid for five minutes, and then with 10 per cent potassium sulphocyanate solution. Each iron speck shows red when the sheet is held up to the light. The glass plate forms a con- convenient holder for the sheet. The red color fades in a few minute^ and count should be taken immediately. Another method is to immerse the paper in 2 per cent potassium ferrocyanide, then in 2 per cent acetic acid, then wash well in water. Hang the sheets vertically until dry. There will be a blue coloration wherever there was an iron speck in the sheet. This method makes a more permanent record than the sulphocyanate treatment. Oil spots. Oil spots are translucent and can be spread or thinned with ether or chloroform. Extraction with either of these solvents removes the oil, unless it is of a peculiar pasty formation caused by use of oily rags in the stock. Mineral oil in rags is prone to form a dirty congealed mass in the washers, which specks the halfstuff with black specks in which mineral oil is the binder. Such specks in the finished sheet are not entirely removed by ether or chloro- form. They are slightly translucent, and unaffected by solution in concentrated sulphuric acid. Color spots. Poorly ground colors such as poor ultramarine give a fine specky appearance usually identified by color only. Alum spots. These are usually pulverized by the pressure of the calender rolls. They are soluble in water and give a slight acid reaction with indicators. This reaction is best watched by dis- solving the speck in a very small test tube and adding the indicator while the tube is under the microscope and against a white back- ground. Coal particles. Coal dust is insoluble and gives no color reac- tions with any reagent. In appearance iron scale can be mistaken for it, and in doubtful cases an iron test should be made on the sheet and the unaffected black particles examined for coal. Under the microscope it can be seen that coal particles in a calendered sheet have been so pulverized by the pressure of the rolls that they shatter very easily when picked with a dissecting needle. Large particles give a characteristic black smear when crushed and rubbed across the sheet. Button specks. Bone buttons ground by beaters or jordans into small pieces come through into the finished sheet as a light colored powdered spot due to crushing in the calenders. A hole is often made at a button speck due to the crushed button piercing the sheet and then partly crumbling out after calendering. Such specks can be differentiated from alum as they are insoluble in water and give no acid reaction with the indicators. Paper specks. In stock made from old papers small undefibered pieces may slide through the screens and form a speck on the sheet. Such specks are fibrous and when lifted out of the sheet they can 'be defibered under the microscope with dissecting needles, showing their identity by this characteristic. Foam spots. Because of the depression left after each foam bubble there is a circular spot more translucent than the rest of the sheet formed wherever foam bursts on the partly formed sheet. The result is characteristic, circular, and translucent as a small round wa^rmark would look. Drag spots. Stock adhering to the slices on the wire forms small uneven lumps when it drags off upon the sheet. These spots are not very common but can 'be recognized as an irregular forma- tion having no foreign material present. Knots. Fabrics in rag stock with knotted threads very often, show the knots in the finished sheet. The knotted thread is easily recognized under the microscope. 5. Starch In addition to chemical tests for the determination of starch in paper, it is possible to determine the kind of starch used. The various untreated starches have characteristic shapes and markings which may easily be identified under the microscope. This is also possible in some cases with treated starches, used in the size-tub. PAPER TESTING METHODS 17 III. PHYSICAL TESTING 1. Effect of Relative Humidity* A superficial examination of the published data will indicate that the physical qualities of paper are affected to a considerable degree (a) Relative Humidity The moisture content of the test sample is affected by changes in humidity, either absolute or relative. Ab- solute humidity is defined as the number of grains of moisture per cubic foot of air at the temperature in question. Relative humidity is defined as the percentage of moisture present, at any particular FIG. 9 Aspen (Populus tremuhides) xlOO (Bureau of Standards). by changes of the moisture content of the test sample. Different FIG. 11 Chestnut (Castanca diirtata) xlOO (Bureau of Standards). kinds of paper as well as different qualities are affected to a differ- temperature, to the amount of moisture present if the air were sat- iMit degree, but certain tendencies are obvious and the importance of urated 9i that temperature. The available data seem to indicate the consideration of the condition of the test sample at the time of that in most cases, the variation of quality of paper bears a relation to relative humidity, rather than to absolute humidity. FIG. 10 Balsam Fir (Abies balsamca) xlOO (Bureau of Standards). test should not be underestimated. The suggestions contained herein are not conclusive nor complete but the conclusions have been de- termined after a careful study of existing data. * The reader is referred to an exhaustive treatment of this suhject in Tech- nical Association Papers, Series VI (1923). FIG. 12 Hemlock (Tsuga canadensis) xlOO (Bureau of Standards). In most testing laboratories that' attempt to control their at- mospheric conditions, a temperature of 70 F. and a relative humid- ity of 65 per cent is maintained. These conditions have ibeen 18 PAPER TESTING METHODS adopted because of work done in the past in Germany and 'because of the increased cost to maintain a lower relative humidity during the warm weather, when the moisture must be taken out of the air by some method of refrigeration. It is not uncommon, however, in steam heated rooms, during the winter, to obtain a relative humidity as low as 15 per cent. and, at 85 per cent relative humidity, the range is from 9 to 14 per cent, with 20 per cent as a possible saturation point at 100 per cent relative humidity. The accompanying curve (Fig. 17) in- dicates in a general way the tendencies of change of moisture content with relative humidity. (c) Weight In general, it may be said that the variation of FIG. 13 FIG. IS Fibers from Rag Pulp xlOO (Bureau of Standards). . Spruce Mechanical Pulp (Picca canadensis) xlOO (Bureau of Standards'). (6) Moisture The moisture content of paper increases with weight due to changes of relative humidity is similar and proper- increase of relative humidity and in -general seems to be independent tional to the variation of moisture content of the paper. The varia- of the furnish, kind of paper, or the method of test. A composite t ; on j n we ight from 15 per cent relative humidity to 85 -per ct-nt average with the moisture content, when plotted, as ordinate and relative humidity seems to be about 6 per cent. FIG. 16 Tulip Tree (Liriodendron tulipfera) xlOO (Bureau of Standards). (d) Bursting Strength Data available at this time in regard lightly concave At 15 per cent relative humidity, the moisture to the effect of relative humidity upon the bursting strength seem content varies from 3 to 7 per cent for different kinds of paper to indicate that bursting strength increases with relative humidity. FIG. 14 Rice Straw xlOO (Bureau of Standards), with relative humidity as the abscissa produces a regular curve, PAPER TESTING METHODS 19 up to about 35 per cent relative humidity and that from that point decreases equally rapidly with increasing relative humidity. This conclusion seems to be assured from the considerable amount of data available but it is not believed that any conversion factor may yet be developed. The amount of variation is widely different for different papers and it seems to 'be evident that long-fibered papers are affected to a greater extent than short-fibered papers. In any case, this variation is quite evident and should be taken into con- sideration when careful and accurate tests are to ! be made. (e) Tearing Strength Very little data are available in regard to the relation between tearing strength and relative humidity but such work that has been done indicates that this test is markedly affected by changes of relative humidity. Tearing strength in- creases to a considerable extent with increase of relative humidity and the amount of this variation seems to be comparable with that in the case of the folding and tensile test. (/) Folding Endurance The effect of relative humidity upon this test seems to be somewhat erratic -with different papers but in any case the variation is very marked. In general, the folding endurance increases rapidly with increase of relative humidity, the machine direction more rapidly than the cross direction. With certain kinds of paper, there seems to be a peak in the curve at 80 to 90 per cent relative humidity with a rapid decline, while with other papers, this peak does not appear. Data seem to indicate that this test is affected by relative humidity to a greater extent than any other. (g) Breaking or Tensile Strength The variation in this test seems to be very similar to that in the case of the bursting strength, but to a greater degree. Strength increases with relative humidity up to a point of about 35 per cent and then decreases at a similar rate. This variation is similar in both the machine and cross direc- tion and in either case seems to be over twice as much as in the case of the bursting strength. 2. Characteristics of Paper (a) Machine Direction: *(3) Several methods are available for determinating the machine direction in a sample of paper. It may sometimes be ascertained by mere inspection of the sheet, as the formation noted on looking through it is often conclusive to the trained observer. The usual machine wire imparts to the sheet of paper a "wire mark" consisting of a series of diamond-shaped marks, the long diagonal of which points in the machine direction. If the wire mark is sufficiently prominent so that its direction can be deter- mined this will establish the machine direction. If the paper is well sized and a circular piece is cut out and moistened on one side by floating on water, it will tend to roll up into a cylinder whose axis is in the machine direction of the sheet. If the paper is unsized it will become entirely soaked through on floating on water and will not curl up. This may be avoided by sizing the paper with an alcoholic solution of rosin or with a solution of gelatine in water, drying and then making the test. Another method of determining the machine direction is to cut two narrow strips of the paper one from either direction, place these one over the other and hold them upright in the fingers. They will droop over of their own weight and if they cling close together the under strip is in the machine direction while if the under slip falls away from the upper the latter is in the machine direction. The form of the break made by the Mullen tester shows the machine direction, as the longest, or chief, line of rupture is always across the sheet. (b) Wire or Felt Side. *(3) In many cases this may be de- termined very easily by a simple inspection but in some papers the wire marks do not stand out at all plainly. Sometimes they may be made more prominent by plunging the sample for a moment into water and draining or blotting off the excess. The moisture causes the fibers to expand, thus undoing the work of the calenders and resorting the texture of the sheet as it left the machine wire. Inspection of a sheet thus dampened will often show that the wire marks stand out plainly, where before they were indistinguishable. This method very often proves satisfactory even for coated papers. 3. Area of Sample For convenience use a straight edge graduated into inches and tenths and read to hundredths of an inch. Calculate area in square itiches. 4. Weight of Sample The sheet-weighing device that indicates the equivalent weight FIG. 17. MOISTURE CONTENT OF PAPER A curve which represents the relation between the percentage of relative humidity and the moisture content of paper. This curve is a composite of data obtained from several sources and under different conditions. in pounds in terms of a 500-sheet ream, is most suitable for labora- tory or mill use. In weighing very small samples, it is not desirable to use a weigh- ing device graduated in terms of a 500-sheet ream. For such cases a chemical balance should 'be used and the weight in grams multi- plied by 1.102, will give the equivalent weight of 500 sheets of the size weighed. Formula for sample weight on sheet paper scales : (wt. in lb.) X (1,000) = weight 25 X 40,500. Area of sheet in sq. in. (wt. in Ib.) X (Area of trade size desired) = wt. of trade size desired. .. Area of sheet in sq. in. It is obvious that the samples being weighed must be accurately measured to determine their size, and this is done by means of an accurate 'rule, graduated in tenths of an inch. The following formula is of assistance, where o is scale reading, 6 is one dimension of the sample, c is the dimension at right angles to b, and d is the num- ber of sheets of paper in the sample: a x 1,000 .= weight in lb. per ream 25 X 40, 500. b X c X d For samples of paper weighing less than 20 lb. on the quadrant scale a chemical balance is used. For convenience, the following formula is used : (Weight in grams) X (1,102) X (1,000) = weight in Ibs. per (Area of samples in sq. in.) X (number of sheets) ream 25 X 40, 500. To convert the weight of the standard ream to the weight of a ream of the desired trade size, it is only necessary to multiply the weight of the former by the area of the latter and divide by 1,000, provided, of course, that the latter ream contain 500 sheets. 20 PAPER TESTING METHODS a. Balances and Scales. There are a number of available as il- lustrated. (Figs. 18, 19, 20, 21.) They may be calibrated by plac- ing small accurate weights in the pan and taking readings on the scale. An average of several readings at uniform distances apart on the scale should be obtained. b. Conversion Factors. The weight of a ream folio size, 17 x 22, 500, can be stated as the substance number. A method for determining the substance number on small samples by the analytical balance is as follows : A flat piece of thin metal cut exactly 2 x 2-1/16 in. is held upon the sample and a sharp instrument run around the edge of the metal. The sample cut exactly 2 x' 2-1/16 in. has a substance number equal to its weight in centigrams. Waight in centigrams X 500 sheets X .374 sq. in. per sheet 45,360 centigrams per pound X 4.125 sq. in. in sample Weight in centigrams X 178,000 substance. = substance number. 187,110 TYPICAL EQUIVALENT WEIGHTS IN STANDARD AND TRADE SIZES* Weight of --earn, Trade size Weight of 25 X 40, 500 ream, 500 sheets Area of sheet ream, trade size Lb. In. In. Lb. 52.6 25 X 38 950.0 50 64.2 17 X 22 374.0 24 100.0 20 X 25 500.0 50 15b.O 22.5 X 28.5 641.3 100 Conversion between ream basis weight and grams per square meter. Weight in grams pe' square meter (Weight in Ib. of any ream, 500 sheets) X 1406.13 Area of sheet in sq. in. FIG. 18. QUADRANT SCALE A typical scale for weighing paper. (Foreign Paper Mills, Inc., New York City). Wt. in Ib. per ream of 500 sheets = (Wt. in grams per square meter) X (Area of sheet in sq. in.) 1406.13 To convert to'lb. , Ream size 0.267, 17 x 22 500 0.714 25 x 40 500 0.429,. . 20-x. 30 ... 0.591 24 x 36 480 0.675 -.25 x 38 500 0.618 24 x 36 500 To convert to grams 3.75 1.40 2.33 1.69 1.48 1.62 Length of paper in a roll. Roll weight Ream area increasing interest in the use of these instruments. The scale. which is engraved on a platinoid circle, is divided into angular de- grees and densities. It is understood that this .type of photometers .is to be produced in this country. 15. Volumetric Composition* (3) The determination of the volume composition of, a paper is at best only an approximation but it is at times desirable' to carry it Fie. 40. SIZING TEST APPARATUS* (112) An elaborate set-up with recording drum for the study of the electrolytic method of determining the sizing quality of paper. (Bureau of Standards.) meter of the paper is calculated. The weight of each substance in grams divided by its specific gravity gives the volume occupied by it, and the sum of all of these volumes subtracted from 1.0 gives the volume of air per cubic centimeter of paper. This method is fairly accurate when only fibers, clay and rosin are present but when other substances are added as in coated papers, the problem becomes more complex and the results less reliable. If the volume of air per cubic centimeter of paper is- the only information needed it may be obtained by determining the actual .pecific gravity by weighing in air and then in oil of known density exactly as in making specific gravity determinations in water. It will be found necessary to expose the paper, submerged in oil, to reduce pressure for some time in order to be sure that all air is removed and replaced by oil. 16. Retention of Loading By retention of loading is .meant that ' per cent of the entire amount of loading material added to the beater, that is retained in the finished product. Secure about a 5-lb. sample of the filler to be used, being careful to select a representative sample. Break up all lumps, spread on a flat surface, divide into four parts, by dividing the pile by two lines at right angles to each other crossing at the center of the pile. Select two opposite quarters, mix and proceed as before. This is known as the "quartering method of sampling." This quartering method is continued until about 25 g. of loading material is ob- tained, which is then placed in a bottle for further use. From this bottle, remove a 1 g. sample, dry at 105 C., to constant weight and calculate per cent of moisture in the loading material. Place the dried residue in a crucible and heat 'at the full heat of a meker burner until a constant weight is secured, then calculate the per cent of water of. composition in the dry clay. (Have clay in a finely divided state and stir frequently during burning.) Secure sample of pulps to be used and determine per cent of moisture and per cent of ash. Weigh the pulp added to the beater. Weigh the clay added to the beater. After running the paper over the paper machine, secure several pieces as a representative sample, dry and make the ash determination on the paper. The above 30 PAPER TESTING METHODS mentioned data used in the following formula will give the per cent of clay used and the per cent retention. Let P = weight of pulp added (in Ih.) C = weight of clay added (in. Ib. ) 'A = Per cent ash in the finished paper. Ap = Per cent ash in the pulp. We = Per cent water of composition in the clay. Mp = Per cent moisture in the pulp. Me = Per cent moisture in the clay. 100 X C (1) % of clay used = P 100 A X P (2) % retention = C (100 A) 100 C (I Me) (3) % of clay used = P (1 Mp) 100P X (A K) (4) % retention = C (100 A K) The value of K is the per cent of filler not derived from the load- ing added. An average value of K is 0.50 so that the formula (4) may 'be used as above or as follows : 100 P (A 0.5) (5) % retention = C (100 A 0:05 Formulas (3) and (5) are recommended for use by the Tech- nical Association of the Pulp and Paper Industry, though (1) and (2) may be used when accuracy is not essential or when the values for moisture content are unknown. Formula (4) does not take into consideration the per cent water of composition in the loading. Where this is known suitable correction may be made. No account is taken of the ash from alum or rosin size as the maximum amount from these factors is probably under 0.05 per cent- and therefore negligible. An ash determination need not be Fie. 41. GLARIMF.TKK A device developed by L. R. Ingersoll for the purpose of measuring the finish or gloss of paper. (Central Scientific Company, Chicago.) calculated beyond the first decimal place. (See ash determination under chemical testing.) An alternate retention formula, developed in the laboratory of the S. D. Warren Company, Cumberland Mills, Maine, is suggested as being of value, as it may be used without making tests that interfere with production of paper. A = Per cent of ash in air-dry stock going to machine. B = Per cent of ash in air-dry paper at reeJ. C Per cent of bone dry filler lost on ignition. 0.94 B (100 100 C A) Retention A (100 100 C B) A and B are considered as whole numbers and C as a decimal. 17. Conducting Particles To show the presence of conducting particles in paper 0.5 or 0.75 mils thick, the sample is placed upon a metal plate which has been polished to a smooth plane surface. This plate is connected in series with 3 dry cells, a model 280 Weston voltmeter of 3-volt range or a similar instrument, and a metal piece which has a per- fectly flat under surface and will be in contact with all parts of the plate upon which it rests. This metal piece is about 1 in. long and l / 2 in. wide and is attached to a handle for convenience in using. FIG. 42. GLARIMETER PRINCIPLE Cut showing the arrangement of lenses and the principle of the Ingersoll glarimeter. (L. R. Ingersoll.) It is called the detector. To test paper, place a measured area upon the plate, make contact with the metal detector and the plate and if there is deflection of the voltmeter indicating that the voltmeter will show any drop in potential that occur when a conductor is be- tween the plate and the movable detector, the instrument is ready to use. Pass the detector slowly over the paper on the plate, using light pressure. When a deflection of the voltmeter indicates that there is a conducting particle in the sheet between the detector and the plate, the position of the detector is marked and it is then moved over the spot at right angles to its former position and the paper marked and it is then moved over the spot at right angles to its former position and the paper marked again when deflection occurs. This locates the particles within a half-inch square and makes it available for microscopic study. Results are expressed in terms of number of conducting particles present per sq. ft. of paper. This instrument is intended for papers of 0.75 mil thick- ness or Jess. With thicker papers, the particles cannot be registered with dependable accuracy because they seldom extend through the full thickness of the sheet. Comparison of iron particles present as shown by chemical tests give numbers far in excess of the number of iron particles that are actual conductors in the sense of spoiling the paper for electrical purposes. This instrument is intended for use in testing papers specified for use in electrical equipment. An additional method is indicated by the accompanying photo- graph (Fig. 44). The small metal piece in the foreground is used as a detector and the presence of a conducting particle is indicated by a click in the telephone receivers. 18. Resistance to Water Penetration Various simple methods have been proposed for this purpose and they are included as they may be of some assistance. A quart mason jar is used in the test. A circular hole of 1 in. in diameter is cut in the metal top and the bottom of the jar is broken out. The sample to be tested is placed in the metal top, between the rubber washer and the metal and firmly screwed in place. The jar may either be filled with water or may be re- versed and partially immersed in water. The temperature of the water should be 75 F. The length of time for penetration of the water will indicate a relative resistance. As in the above case, a circular hole of 1 in. in diameter is cut in the metal top, the sample placed in the top between the rub- ber washer and the metal, a bone-dry weighed sample of absorbent cotton or paper is suspended in the jar, the lid put on and the jar reversed and partially immersed in water at 70 F. After a prede- PAPER TESTING METHODS 31 termined length of time, the absorbent cotton or paper is removed and immediately weighed. The increase in weight will indicate a relative value for moisture penetration. A modification of the Stockigt method may also be used as a means of determining the relative water resisting quality of paper. For routine tests, the samples may conveniently be cut about 2 1 /* in. square and molded into a cup-shape in the top of a bottle by depressing the paper into the top of the bottle with the stopper. The top of the bottle should be about V/2 in. inside diameter. A ground glass bottle and stopper are best suited to the purpose. At least three test "cups" should be prepared from each sample to be tested and the average result taken as an indication of the degree of water-proofing. A number of samples may be tested at the same time by using a wide flat-bottom pan or dish. Enough of the 2 per cent ammonium thiocyanate (NH 4 CNS) solution to cover the bot- tom of the dish and float the "cups" is used. After the "cups" have been floated and the time recorded,, place three or four drops of the 1 per cent ferric chloride ( FeCl 3 ) solution in the middle of each cup as quickly as possible, taking care not to drop any of it into the other solution. A large dropper is- convenient to use. Spread the ferric chloride out over the bottom of ea-.-h cup with a glass rod, taking care not to spread it out far enough to touch the bend. For where the paper is bent or folded, the solution will penetrate more rapidly and give erroneous results. The layer of ferric chloride solution should be fairly thin because it has a reddish color and may interfere with one's judgment of the. reaction if it is too thick. The time required for the pink or red coloration to set in is taken as a measure of the degree of water-proofing. On samples it will be found that only a single point of color is seen. This is probably due to a "pin hole" or fault and should be noted, but not taken as the "end point." The color should be fairly general and pronounced before the solution is considered through. Note-^-Fritz Stockigt, Wochenblatt fiii- Pnpierfabrikation, 1920, pg. 39; translation Paper, March 10, 1920. C ^ TAPPED HOLES TOR STAND. FIG. 43. MARTIXS-KOENIG PHOTOMETER A sketch of a photometer used for Ingerscll glarimeter. (Courtesy of Adam Ililger, Limited, London.) IV. CHEMICAL ANALYSIS 1. Ash Determination (a) Quantitative A 1 g. sample of the paper to be tested is burned in a porcelain or nickel crucible. A Meker burner is very convenient for this purpose, as some heavily loaded papers require considerable time and heat to burn the last traces of carbon. Ordinarily a white paper will give a white ash, but if mineral pigments have been used the ash is likely to be colored. In any case the ash should be free from specks of unburned carbon. During the burning care must be taken that a portion of the ash is not lost by air currents. The ash is often light and fluffy, and the strong currents of air from the burners may blow away a por- Note The sample of paper need not be weighed closer than 0.005 g., since a 1 per cent variation in the moisture content will introduce an error of 0.01 g. If the maximum error in the weight of the paper is 0.01 g. then the maximum error in the weight of the ash will be 0.01 g. for every 10 per cent of ash present. Therefore in a paper containing 10 per cent ash, the results will be reported to the nearest tenth. If special accuracy is required, the paper may be weighed in the bone dry condition. Then with the error due to moisture eliminated it is possible to weigh the paper to 4- 0.0005 g. and the error will be 0.0001 g. for every 10 per cent of ash. The results may then be reported to the nearest hundredth. This latter result will of course be 1 per cent lower 1 g. sample containing 10 per cent of moisture. than the ash results on a FIG. 44. CONDUCTING PARTICLES An arrangement for easily determining the presence of conducting particles in thin paper, such as condenser paper. (Pittsfield Works Laboratory, Gen- eral Electric Company.) (Bureau of Standards.) tion of it. While cooling they may be kept in a dessicator, but this is not necessary, since the ash may be poured into a counter- poised aluminum pan as soon as the crucible is cool enough to avoid the danger of loss from convection currents. The ash will cool almost instantly and may be weighed at once. This saves the time required for the crucible to cool and also avoids the necessity of weighing the crucible. Note Aluminum is recommended as being less easily broken as well as lighter, than glass. The ash as finally obtained includes all non-volatile and non- combustible matter in the paper. It may be derived from at least five sources : (1) The ash of the pulp from which the paper was made; (2) the ash from the various loading or filling materials added; (3) the ash from any surface coating or sizing, and (4) the ash of mineral coloring materials or pigments, and (5) the ash derived from alum used, though the amount traceable to this cause is very small and may be neglected. The complete quantitative analysis of an ash is a time-consuming and also a rather complicated pro- cess. It is possible, however, to obtain some idea of the composition of the ash by a few comparatively simple tests. Once the paper is burned it is impossible to tell which portion of the ash is derived from the coating and which portion is derived from the filler. Therefore, if anything more than the total ash content is desired the coating must be stripped from the paper before ashing. In the case of coated papers where casein has been used as the adhesive, this can often be done by the use of dilute ammonia. The insoluble material may be filtered off, dried and weighed. The filtrate may be evaporated to dryness and the residue weighed. This will include the casein (or soluble casemates if such be present) as well as any soluble material present. The difference between the weight of the total ash and the ash of the 32 PAPER TESTING METHODS paper from which the coating has been stripped plus the weight of the coating will give the weight of the combustible portion (i. e. glue or casein) of the coating. Note Provided the insoluble portion of the coating has been ignited to the same extent as the total ash. It is quite possible for a paper to have an ash of 3 to 5 per cent without being loaded. This might be due to the ash in the pulp, as well as to the ash derived from water color, alum and sizing materials. Where the ash is 5 to 20 per cent the paper is loaded. A list published in Paper *(70) gives the names of twenty-one loading materials. However, from the chemical standpoint many of these are practically the same material sold tuidcr different names. They are all silicates, sulphates or carbonates of aluminum, mag- nesium, barium or calcium. While an analysis will give the com- position of the ash, it will not tell under what trade name the material may have l>een bought. In this connection it is interesting to note the following percentages of ash in fibrous raw materials as given by Wrede. (Paper, Jan. 31, 1912)* (3). Stock Bleached linen hal f stuff Bleached cotton half stuff Unbleached cotton half stuff Sulphite, unbleached Soda Adansonia Japanese fibers Ash % 0.121.86 0.240.79 0.241.12 0.481.25 0.361.40 5.707.19 2.5 (b~) Qualitative *(4, 11, 69). To determine the kind of load- ing or coating material used, it is necessary to test the ash quali- tatively, for which purpose at least 0.2 g. of ash is desirable. Brief- ly, tests should be made for the substances indicated in table, in which are also given the fillers that the presence of these sub- stances would indicate. PAPER FILLERS AND THEIR INDICATORS *(91) Substance Calcium sulphate . . Calcium carbonate . Barium sulphate . . Magnesium silicate Aluminum silicate . Filler indicated Crown filler Chalk Blanc fixe Talc China clay These fillers have various trade names and do not in all cases have definite chemical formulas, but the presence of any great amount of any of the materials in the first column would indicate the kind of filler used, and further confirmatory tests may be made. Burn enough paper to obtain at least 0.2 g. ash in a platinum or nickel crucible. Separate 1/3 of the ash from the main portion; to this 1/3 add 5 cc. water and boil until well extracted ; lilter ; add a drop of hydrochloric acid to the filtrate and then 3 cc. 10 per cent barium chloride solution. A white precipitate is due to calcium sulphate or crown filler in the paper. To the residue from the water extraction add dilute hydrochloric acid. Effervescence of carbon dioxide gas is due to chalk in the paper. This test for chalk may lye applied directly to the paper before ignition if the presence of chalk is suspected at the start. To the 2/3 portion of the ash add 1 g. sodium carbonate and mix well. Fuse the mass in a platinum crucible until it becomes a clear quiet liquid. Cool and dissolve in boiling dilute hydro- chloric acid. This solution should be clear. If an undissolved white residue remains, filter this off. It is probably due to barium. Dip a clean platinum wire in this residue and hold it in a bunsen flame. Barium will give a characteristic green color. This shows the presence of blanc fixe. If the previous hydrochloric acid solution was clear evaporate nearly to dryness. Dip a clean platinum wire in this mass and test for barium as given above. Then take up the mass with dilute hydrochloric acid ; boil ; filter. The residue is silica from silicates in the filter. A portion of this filtrate can be used as a confirma- tory test for sulphates. To the filtrate from the silica separation add ammonium hydroxide until slightly alkaline. A white floccu- lent precipitate shows the presence of aluminum. Filter off this precipitate and make the filtrate acid with oxalic acid. Make alka- line slowly with ammonium hydroxide. The formation of a white precipitate shows the presence of calcium. Filter off this precipi- tate and make the filtrate alkaline with ammonium hydroxide. Add 5 cc. saturated solution of sodium acid phosphate and stir with a rod. There will be a crystalline precipitate formed if magnesium is present. It forms slowly and is best brought down by an occasional rubbing of the sides of the beaker with a stirring rod. These tests indicate the possible combinations of elements in the filler. Where there are several names for one chemical com- bination such as talc, asbestine, agaiitc, etc. for various mag- nesium silicates a microscopic analysis and comparison of the. crystal form with known samples is necessary. Quantities of al- uminum invariably indicate clay. Silica and magnesium indicate talcs, agalitcs or asbestine and water-soluble sulphates from filler point to calcium sulphate. *(12). If the paper contains calcium sulphate, the ash obtained may consist partly of calcium sulphide, due to reducing action of the carbon found on ignition, and the amount will, therefore, not represent the true amount added. The ash should be moistened with a few drops of sulphuric acid, and again ignited, in order to reconvert it into calcium sulphate. It should also 'be borne in mind that the sulphate of lime as present in the paper is combined with two atoms of water (CaSO, -j- 2H : O), and, therefore, that every part of calcium sulphate obtained represents 1.26 parts of pearl-hardening actually in the paper. (c) Amount of Coating. *(11). Weigh a piece of the paper cut exactly 2 x 5 in. and place in a flat glass dish. The dishes used for developing in photography are convenient for this pur- pose. Cover with water containing 1 per cent of NH,OH and set aside in a warm place (2 or 3 hrs. is generally sufficient to loosen the coating). Remove the paper to a large watch glass, rub the surface with a small camel's hair brush cut off square, and wash the coating into a beaker. If the paper is double-coated, turn it over and repeat on the other side. Continue the operation until all the coating is washed into the beaker. Dry the paper and weigh it under the same conditions as those under which the original paper was weighed. The loss in weight is the weight of coating. Calculate this to per cent of the original sample and also figure the weight of coating on the basis of a ream of 25 x 40, 500. 2. Paraffin There are several paraffin solvents which may lie used for this determination. Gasoline is easily obtained and comparatively cheap. It has, however, the serious disadvantage of being very inflam- mable. Carbon tetrachloride (CC1.) is not combustible. It is superior to chloroform, since the fumes are not likely to -produce anesthesia. Both gasoline and carbon tetrachloride have lx?en found satisfactory. Note Carbon tetrachloride cannot be kept in ordinary "tin" cans on ac- count of its actitn on iron. Enough of the paper must be taken to obtain a weighable amount of paraffin. One or 2 g. of paper should be sufficient. Place the paper in a soxhlet or in an ordinary erlenmeyer flask fitted with a reflux condenser, cover with gasoline or carbon tetrachloride and extract until the paraffin is all dissolved. If the erlenmeyer flask be used it will probably be necessary to make a second extraction with a fresh amount of solvent. The solution may then be evaporated to dryness and the paraffin weighed. If the paraffin shows a tendency to "creep" over the edge of the dish it may be easier to weigh the paper before and after extraction and consider the loss in weight as paraffin. The following qualitative test for paraffin known as the Dunlofi PAPER TESTING METHODS 33 method may be of value for determining the presence of paraffin in the presence of rosin : It consists in boiling the sample with acetic anhydride and ob- serving the behavior of the solution on cooling. If paraffin is present the anhydride becomes turbid and the paraffin separates out on the top in a white precipitate. Less than 1 per cent of paraffin may be detected in this manner. (Allen's Commercial Organic Analysts.) 3. Sizing Materials a. Kosiii..fiiiiiniet Method: Alcohol-ether Method. *(103). Cut 5 g. of paper into strips approximately l / 2 in. wide and fold them into numerous small crosswise folds. Place the folded strips in a soxhlet. extractor and fill with acidulated alcohol. Acidulated alcohol solution is made by adding 900 cc. of 95 per cent alcohol to 95 cc. of distilled water and 5 cc. of glacial acetic acid. Place the soxhlet flask directly in the boiling water of a steam bath and extract by siphoning from six to twelve times, according to the nature of the paper. Wash the alcoholic ex- tract of rosin, which may contain foreign material, into a beaker and evaporate to a few cc. on a steam bath. Cool, take up in about 25 cc. of ether, transfer to a 300 cc. separatory funnel containing about 150 cc. of distilled water to which has been added a small quantity of sodium chloride to prevent emulsification, shake thor- oughly and allow to separate. Draw off the water into a second separatory funnel and repeat the treatment with a fresh 25 cc. portion of ether. Combine the ether extracts which contain the rosin and any other ether-soluble material and wash twice or until the ether layer is perfectly clear and the line between the ether and the water is sharp and distinct, with 100 cc. portions of dis- tilled water to remove salts and foreign matter. Should glue which is extracted from the paper by alcohol interfere by emulsifying with the ether, it may be readily removed by adding a strong solution of sodium chloride to the combined ether extracts, shak- ing thoroughly and drawing it off, repeating if necessary before washing with distilled water. Transfer the washed ether extract to a weighed platinum dish, evaporate to dryness and dry in a water oven at from 98 to 100C. for exactly one hour, cool and weigh. This length of time is sufficient to insure complete drying. Prolonged heating causes a continual loss of rosin. Some objections have 'been made to portions of the foregoing method. It has been stated that the sodium chloride is sufficiently soluble in the ether to produce high results. Some also prefer to carry the evaporation of the alcohol extract to complete dryness and then take up in ether and in water. The residue as obtained is only partially soluble in ether, but in case the entire amount of ether-soluble material should not be secured, after as much has been dissolved by the ether as possible, the remainder of the resi- due is taken up in water. The ether and water is then separated in a separatory funnel in the usual manner. There appears to 'be no reason why a glass dish should not be as satisfactory as a platinum dish. It is also asserted that the extraction may be carried out in an erlenmeyer flask instead of a soxhlet. The num- ber of extractions required depend upon the character of the paper used. In some individual cases it has been found that a single extraction took out practically all the rosin. This extraction was done on a hot plate and the alcohol was in contact with the paper for about half an hour. It is not known to what extent this time could be shortened or in what per cent of cases a single extraction would be sufficiently accurate. Note for extractine rosin, the apparatus shown in Fig. 43 will do the work of a soxhlet extractor with greater convenience. It is essentially the same as the soxhlet in principle, but can be set up very quickly, takes less solvent, keeps the crndensed solvent surrounded by hot vapors, occupies less spaces and is less liable to breakage. The time of extraction is lessened be- cause of more frequent flushing of the small well with the condensed solvent. This apparatus is listed as an Undem-riter's Extractor, and has been exten- sively used in the extraction of rubber. QUALITATIVE TEST FOR ROSIN. Boil a small portion of the paper in 5 cc. acetic anhydride in a dry test tube. Cool. Add carefully down the side of the test tube a small amount of concentrated sulphuric acid. The development of a pink ring shows the presence of rosin. Rosin *(3) is used almost exclusively in the beater to impart waterproof properties to the paper. There is no single test of a simple nature which will demonstrate positively the presence or absence of rosin and any judgment regarding it must be based on the indications of a number of different tests. If a little ether is dropped onto a sheet of paper and allowed to evaporate there will be formed, in the case of rosin-sized paper, a ring of rosin at the edge of the zone where the ether evaporated. . This will be absent in most unsized papers, and it will, of course, be formed in any- paper which contains any ether soluble material besides rosin. Another test is made by boiling a little of the paper for a few minutes in glacial acetic acid and pouring the acid into a little FIG. 45. ROSIN EXTRACTION A simple apparatus for determining the rosin content of paper (American Writing raper Company, Holyoke, Mass.) distilled water. A pronounced turbidity indicates rosin, but a slight opalescence may be caused by other soluble substances and must be disregarded. A third test is that known as the Raspail reaction. If a drop of concentrated sulphuric acid be placed on the paper and a grain or two of sugar added a pronounced raspberry red -color will develop with rosin-sized papers, while with unsized papers red color is also formed when albuminous materials are present so they must first be proved absent before the test can be considered indicative of rosin. (fe) Glut and Casein. There appears to be no quantitative method known for the determination of these materials in the presence of each other. Both substances contain nitrogen. If only one be present and the nitrogen content of the original ma- terial as added to the paper be known, then by means of the nitro- gen determination the content of glue or casein may be determined. QUALITATIVE TEST FOR GLUE. Boil a small portion of the paper with 10 cc. of water in a test tube. Decant the extract to another test tube and cool. Then add 5 cc. of ammonium molybdate solution, followed by a few drops of nitric acid. The formation of a white amorphous precipitate shows presence of glue. 34 I 'A PER TESTING METHODS DETERMINATION OF NITROGEN Place from 3 to 5 g. of the paper which has been cut into small pieces in a kjeldahl digestion flask, add ten g. potassium sulphate, 0.7 g. of mercury and 25 cc. of concentrated sulphuric acid. The mercury acts as a catalytic agent aiding in the decomposi- tion of the nitrogenous material. The potassium sulphate serves to raise the boiling point of the sulphuric acid. It is probable that sodium sulphate can be used in place of potassium sulphate, but it is recommended that 15 g. of sodium sulphate crystals be used in this case. Heat gently at first to avoid frothing and finally increase the heat as the digestion proceeds. At the finish the solution should be colorless, or of a pale straw color, and of a syrupy consistence. At the completion of the digestion, which may require one and a half to two hours, the contents of the flask are allowed to cool and 30 cc. of a 4 per cent solution of potassium sulphate arc added. The potassium sulphate is necessary to break up nitrogen com- pounds of mercury. Other materials than potassium sulphide have been used for this purpose, but are not recommended. Before the distillation can be made the mass must be rendered alkaline. First dilute with about 200 cc. of distilled water and then neutralize by adding an excess of saturated solution of sodium hydroxide. The volume of the solution after the sodium hydroxide has been added should be about 400 cc., therefore the volume of water added must be calculated so that just enough room would be left for the sodium hydroxide solution. Commercial sodium hydroxide (95 per cent) has been found satisfactroy. There should be an excess of caustic soda equal to about 5 cc. of a saturated solution. It is convenient to add a few drops of methyl orange indicator or phenolphthalein indicator solution to the flask before adding the sodium hydroxide. The solution will become yellow or red respectively when it becomes alkaline. The sodium hydroxide solution is carefully poured down the side of the flask so that it does not mix with the contents. The flask is immediately connected to the condenser and then the flask is shaken in order to thoroughly mix the contents. If about 5 g. of granulated zinc or a few small pieces of pumice .stone are added to this flask just before the sodium hydroxide, they will help to prevent bumping. The distillate is caught in a flask containing a known amount of standard acid diluted to a volume of -100 cc. with distilled water. (The equivalent of 30 cc. n/10 normal acid should be ample.) A few drops of indicator should be added to this solution. Sodium alizarin sulphonate and methyl red have been recom- mended as indicators. The end of the condenser tube should dip beneath the surface of the acid. The distillation should continue for 45 min. and the distillate should equal 200 cc. Titrate with n/10 normal alkali. This same operation of distillation should be carried out, using only the chemicals involved in order to have a check on their purity. This is known as the "blank." .Subtract the number of cc. of n/10 normal alkali required to neutralize the distillate, from the number of cc. required by the Wank. This difference is the number cc. of n/10 normal alkali equivalent to ammonia. No. cc.X0.014=g. nitrogen. The following factors should be used on unknown samples : For casein use the factor 6.3 and for glue use the factor 5.6. In all cases this factor should be determined wherever possible, as those values will vary, depending on the grade of material used. Note Copper sulphate, weight for weight, can be substituted for the mercury as a catalytic agent in this determination; it serves as an indicator for alkalinity by turning a characteristic blue when the solution is made alkaline previous to distillation. Small glass beads can be effectively sub- stituted for granulated zinc to prevent bumping in the distilling flask. Casein *(3) may be detected in paper by moistening the sample with Millon's reagent and wanning gently either over a flame or over an open steam bath. If casein is present a brick-red color _ will develop. In the case of coated paper in which much satin white is used, the alkali present determines the formation of a yellow color. In this case proof may be obtained by moistening the paper first with dilute nitric acid, to neutralize the alkali, and then applying the Millon's reagent as before; tested in this way satin white coated paper will give the usual red color. Casein may also be detected by boiling the paper with water and a few drops of ammonia, filtering and adding to the filtrate dilute acetic acid very gradually. Casein will precipitate when the solution becomes very faintly acid, but it may redissolve on adding a con- siderable excess. This test is also given, though usually less strongly, by rosin, so the precipitate should be tested with Millon's reagent to confirm the presensc of casein. Casein is seldom used except in the coating; cases of surface sizing or of its use in the beaters are very rare. Glue *(3) is sometimes used as an adhesive in coating papers and in rare instances in the beaters : the better grades known as gelatines are used in surface sizing. If glue is present alone it may 'be detected by boiling the sample of paper in water, filtering if necessary, and adding a little dilute tannic acid solution ; a grayish, flocculent precipitate indicates glue. Casein is also pre- cipitated by tannic acid and the presence of starch prevents the precipitation of glue so that when either casein or starch is present there is apparently no means of proving the presence or absence of glue. r. Starch: Procedure for Analysis. The paper to be analy/.ecl is tested with the usual iodine reagent. If but a trace of starch is present, no acetic acid is required in extraction. A 5-g. sample is cut into small pieces and placed in a 500-cc. round-bottom nask. 200 cc. of water is added, and 5 cc. glacial acetic acid is run in. making a 2'/ 2 per cent solution. The flask is connected with a reflux condenser by means of a clean rubber stopper and the contents boiled vigorously for I 1 /; hrs. The extract is decanted through a Biichner funnel equipped for suction filtration and the pulp washed with about 50 cc. of hot water. To the filtrate is added 15 cc. of HC1 (37 per cent) and boiling continued for 30 min.. the volume of the solution being permitted to decrease by evaporation to al>out 200 cc. The hot acid solution is neutralized by the addition of solid sodium carbonate until effervescence ceases and the volume is determined. This solution is titrated into a measured quantity of Fehling's solution (2 to 10 cc., according to the amount of starch present). After each addition of sugar solution the mixture is heated to the boiling-point' and maintained at that temperature for 1 min. The reaction mixture may be diluted if this is considered desirable. The end-point is determined on a spot plate with a potassium ferrocyanide-acetic acid solution and is that point at which no immediate color is produced on tin- plate : it may be determined to within V* to 1 cc. of sugar solution, depending on the volume of solution employed. It was found that the potassium ferrocyanide became colored when allowed to remain a number of days with the acetic acid, and that a sharper and more distinct end-point can be obtained if the acid is added separately to the spot plate when the test is to be made. One drop of each solution is used for a test. QUANTITATIVE ANALYSIS FOR STARCH* (120) Method of Kannn ami I'norlices. PREPARATION OF RKAGK\TS The usual Fehling's solution is em- ployed. Solution A 69,3 g. of crystallized copper sulphate arc dissolved in water and the solution diluted to 1,000 cc. Solution B 346 g. of Rochelle salt and 120 g. of si ilium hydroxide are dissolved in water and the solution also diluted to 1,000 cc. Sofutions A and fi are kept separate and equal volumes mixed when ready to be used. In a given experiment, where it is reported PAPER TESTING METHODS 35 that 10 cc. of Fehling's solution is used, it is understood that 5 cc. of solution .-I is added to 5 cc. of solution B. According to the literature, 10 cc. of such a solution should be equivalent to 0.05 grains of dextrose when an analysis is run in a specified empirical manner. It is found more convenient to standardize the solution with a known quantity of starch, the latter being hydrolyzed and titrated under the same conditions used later for the hydrolysis and titration of starch in paper. The advantage is obvious. Potassium fcrrocyanidc solution. A 10 per cent solution of K,Fe(CN)3H t; O is used. Acetic acid solution. A 50 per cent solution of acetic acid is found convenient. METHOD OF CALCULATION OF RESULTS It has already been suggested that Fehling's solution be stand- ardized against one of the ordinary starches used in paper manu- facture. Such a procedure is justified by the close agreement in the reducing values of corn-starch, Hercules gum, feculose and dextrin. Example A sample of corn-starch was dried at 105 C. for 3 hrs. A .05-g. portion was then weighed out and hydrolyx.ed with about 190 cc. of a 4 per cent HC1 solution during a period of 30 min. After neutralization with solid sodium carbonate, the final volume was adjusted to 200 cc., and the solution titrated against 10 cc. of Fehling's solution ; 20 cc. of sugar solution were required and 10 cc. of Fehling's solution are therefore equivalent to 20/^00 X O.SO 0.050 g. starch. In an analysis of a 5-g. sample of paper the volume of the final hydrolysis mixture was 217 cc. Of the latter solution 39 cc. were required for reaction with 10 cc. of Fehling's solution. The per cent of starch in the sample of paper is therefore : 217 Yalm- of Fehlins's solution in g. of starch X 100 = 5.5 per cent 39 Wt. of sample of paper Since, however, a 5-g. sample of paper is used, and since our Fehling's solution is equivalent to 0.05 g. starch to 10 cc. of solu- tion, the calculation is simplified thus : 217 39 = 5.5 pr cent starch. Mention might be made of the polarimetric method of Dr. C. E. G. Porst and H. A. Crown. See Journal of Industrial and Engi- neering Chemistry, vol. 5, No. 4, April, 1913. QUALITATIVE TEST TO INDICATE ITS PRESENCE IN PAPER Make a dilute solution of iodine in potassium iodide by adding a small amount of water to a mixture of three or four crystals of iodine and 1 g. of potassium iodide, stirring until the iodine is completely dissolved, and then diluting the solution with pure water until a pale straw-yellow color is obtained. Add a drop of this solution to the paper under examination, a blue color indicates the probable presence of starch. If this blue coloration is obtained it is well to confirm the test by boiling the paper with water and testing the water extract with the iodine solution, because cellu- lose in the presence of water when subjected to certain mechanical processes gives rise to modifications known as hydrocelluloses. These hydrocelluloses are not soluble to any great extent in boiling water, but they will give rise to a blue coloration when brought into direct contact with the iodine solution. An alternate procedure is as follows: The universal test for starch *(3) is to apply a dilute iodine solution to the paper when a blue to violet color will appear if starch is present. It is well to confirm this test by boiling some of the paper with a little water, filtering and testing the filtrate, after cooling, with a few drops of iodine solution. This is necessary because hydrocelluloses, which are only slightly soluble in boiling water, also give a blue color when brought into direct contact with iodine solution. Micro- scopic examination will show whether the starch granules have been burst by boiling or whether the starch was used without cooking. If the paper to be tested is torn so that it splits on the edge before being moistened with the iodine solution it is generally possible to tell whether it is surface sized or not. If it is surface sized only, the interior of the sheet will remain white while the surface will turn blue ; if, however, considerable starch was used in the beater, this is in part cooked and drawn to the surface by the heat of the driers so that the paper has the appearance of being surface sized when in reality it was not. Microscopic examina- tion of the papers after treating with iodine will sometimes enable an opinion to be formed though it is seldom possible to prove positively in such a case whether the paper is surface sized or not. d. Dextrine in Presence of Beater Starch. Method of Kamm and Tendick. *(119). The procedure adopted consists in the re- moval of the surface sizing by a 45-min. leaching of the sample of paper with water at a temperature of 60 C. For a 5-g. sample 200 cc. of water is used. The extra is removed by suction filtra- tion and the soluble carbohydrate material hydrolyzed and estimated according to the procedure already described in detail. See Method for quantitative determination of starch. The starch remaining in the paper may then be isolated by the dilute acetic acid extraction method recommended in the article on starch determination. 4. Chlorine The determination of free chlorine in paper is carried on in a manner similar to that used in testing half-stuff; namely, take a small mass of the stuff to IK- tested, from the beater, press it with the hand and test with a few drops of potassium iodide starch solution. If free chlorine is present the characteristic blue color will be developed. For the testing of finished paper the determination is best carried out as follows. Cut the paper into small pieces, moisten with dis- tilled water, and test with starch iodide paper ; this is best done on a glass plate. Instead of starch iodide paper one may mix a small piece of starch to a paste with cold water, and mix it with a solution of potassium iodide. 5. Sulphur *(127) The apparatus consists of a 500 cc. round bottom flask with a neck about 2 in. long and 1 in. in diameter. The mouth of this neck is ground to a flat surface and on this is placed a glass tube about 4 in. long and 1 in. in diameter, the lower end of which is also ground flat to fit tightly upon the upper surface of the neck of the flask. The whole is so arranged that after placing a piece of filter paper between the two ground surfaces, the tube and flask can be securely clamped together so that all gas gener- ated in the flask must pass through the filter paper and then up through the superimposed glass tube. The procedure for the testing of tissue papers is as follows : A sample of 25 sq. in. is taken and its weight determined. It is then shaken up in a wide mouth, glass-stoppered bottle with 10 cc. of distilled water ; when partial disintegration has taken place, another 10 cc. of water is added and the shaking continued until the paper has been completely reduced to pulp. The larger part of the pulped mass is now transferred to the flask described above, and the residue which is left in the bottle is rinsed into the flask with a mixture of 10 cc. of water. Prepare turnings from the highest grade, pure stick zinc, which must be free from sulphur and arsenic. Treat 1 g. of these turnings with 10 cc. of a dilute solution of copper sulphate con- taining about 0.002 g. actual copper. After a few minutes all the copper will have deposited and the turnings are then thoroughly washed to remove every trace of zinc sulphate. The turnings are added to the flask and a wad of cotton inserted in its neck. Between the two ground glass surfaces is then clamped a piece of filter paper about 2 in. square which has been per- forated with small pin holes about Hi in. apart and which just 36 PAPER TESTING METHODS before use is moistened with several drops of lead acetate solution. Finally a loose wad of cotton is placed in the tube above the paper. The flask is placed on the steam bath and allowed to stay, with occasional shakings, for an hour. The filter paper is then removed from the neck of the flask and air dried. It is best compared with the standard test pieces by placing them side by side on a piece of white paper and covering them with a thin piece of clear, white glass. The standard test pieces are prepared by using sulphur- free cotton in the flask instead of the disintegrated paper and adding to this definite volumes of a very weak solution of sodium thiosul- phate whose strength is accurately known. The sulphur-free cotton is prepared .by boiling absorbent cotton in weak caustic soda solu- tion and washing thoroughly with distilled water. The sensitiveness of this test is such that the presence of 0.000001 g. of sulphur in the flask will give a distinct color on the lead acetate paper. From tests of a considerable number of papers which have been found satisfactory in actual practice it has been proved that tissue paper is safe for wrapping silverware if it does not contain more than O.C00002 g. of sulphur per 25 sq. in. of paper (atout 0.25 g.) ' 6. Coloring Matter *(28) Smalts, existing as it does in high-class papers, usually without admixture with loading materials, can be estimated with sufficient accuracy by incinerating the paper, weighing the ash, and making a correction for the small proportion of the latter due to the fiber, etc. This proportion does not usually exceed 2 per cent. The ultramarines are of variable and even doubtful composition, and are, therefore, best estimated by comparing the depth of color of the ash with that of standard mixtures of the pigment with known proportions of china clay. Chrome yellow, crant/c, etc., also of variable composition, may be determined, if necessary, by estimating the lead and chromium separately, and calculating the results to the nearest indicated com- position. It is scarcely necessary here to describe the full gravi- metric process as it is likely to be but rarely required. It will be sufficient to say that the lead is precipitated and estimated as the sulphate, and the chromium as chromic oxide. Prussian blue may be determined approximately by estimating the iron by ' igniting the paper, fusing the ash with sodium car- bonate, treating the fused product with hot water, filtering, and boiling the residue with dilute hydrochloric acid and a drop or two of nitric acid. The solution is then again filtered, and the iron and alumina precipitated with ammonia in the presence of a little ammonium chloride. The precipitate of iron and aluminum hydrates is washed, filtered off, and digested with excess of caustic soda, then filtered ag'ain and carefully washed. The residue, which con- sists entirely of iron, is washed, dried, ignited, and weighed as the oxide. This process also serves for the estimation of all other iron pigments except the natural figments, ochres, etc. 7. Tests for Special Materials *(28) Oils and fats can be estimated by extracting with ether, evaporat- ing the solvent, and weighing the residue. Paraffin -ttw.r Similar to the above, using benzin or petroleum spirit. Salicylic Acid This substance is used as a preservative in papers required for wrapping foodstuffs. It is extractable with petroleum ether, and may be estimated in the solution by diluting the latter with an equal volume of 95 per cent alcohol and titrating with n/10 normal alkali, using phenolphthalein as indicator. Each cc. of n/10 normal caustic soda is equivalent to .0138 g. of salicylic acid. Carbolic Acid The estimation of carbolic acid in carbolized wrapping paper is frequently required. Commercial carbolic acid consists chiefly of cresylic acid with higher phenols, but little real phenol being usually present. Since, however, cresol is probably as efficient an antiseptic and insecticide for ordinary purposes as phenol, the absence of the latter body is of little importance. Car- bolic acid may contain tar oils, which are, however, quite inert. Naphthalene is also liable to be present. For the estimation of commercial carbolic acid the bromine- absorption method in use for the determination of phenol is value- less. The writer has found the following method, which is based on a process originally described by Muter, quite satisfactory: From 10 to 20 g. of paper (according to the probable proportion of acid present) are cut into pieces and extracted with a sufficient quantity of alcohol (95 per cent) in a soxhlet. The extract is transferred to a basin, mixed with about half its volume of a 10 per cent solution of caustic soda, and the mixed liquids evaporated in the water bath to small bulk. Tar oils and naphthalene, if present, here separate out and may be removed by filtration. The liquid is now transferred to a separating funnel and hydrochloric acid added cautiously and with gentle shaking until the liquid shows' an acid reaction. Means should be taken to prevent the mixture becoming too hot during the process. A little brine is now added. The liberated tar acids rise to the surface of the liquid which also becomes milky from the precipitation of rosin. The whole is now set on one side for a short time to complete the separation of the layer of tar acids, after which the resinous liquid is drawn off as completely as possible. The residue of oil is shaken up with ether or petroleum spirit, transferred to the weighed flask, the -solvent evaporated off, and the residue weighed. 8. Free Acid in Paper Weigh 10 grams of the paper to lie tested, tear into small pieces, place in a 250 cc. porcelain casserole, and cover with a small amount of distilled water. Heat gently for an hour over water bath or electric hot plate. Pour off water and wash with small quantities of distilled water, adding it to water extract. Another casserole is filled with an equal amount of distilled water, to which is added two drops of a methyl orange solution (0.1 per cent solution in water). To the former is then added tenth normal standard solution of caustic soda until the color matches the sample. The acidity is then expressed in terms of sulphuric acid (rLSO,). An alternate method is as follows : Take' a piece of the paper six inches square, place in a saucer, and pour over it distilled water, and work about with a glass rod for 5 or 6 min. Now take a blue litmus paper or a little tincture of litmus and test the extract, when if either turn red it shows the presence of acid. Divide the extract into two parts ; to one add a few drops of nitric acid, then nitrate of silver solution, when if a white curdy precipitate is formed, it proves the presence of hydrochloric acid or chlorides. To the second portion add a few drops of hydro- chloric acid, heat to boiling in a test tube, and add a solution of barium chloride; a white precipitate indicates the presence of sul- phuric acid or sulphates. 9. Tarnishing Test *(11) A paper which is to be used for wrapping silverware should be essentially free from active sulphur compounds. The method of testing so called "anti-tarnish" paper consists, in general, of com- paring the sample to be tested with special papers impregnated with 0.001 per cent and 0.0001 per cent Na : S solutions, the sul- phide test in each case being made under prescribed conditions by a hydrogen evolution method and lead acetate paper. Preparation of Special Impregnated Papers. Make the special papers from 10 cm. best white filter paper, each of which weighs approximately 0.6 gram. Prepare the following solutions : a. Dissolve 3 grams of fresh sodium sulphide crystals in 100 cc. of distilled water. (3 g. of Na = S9H...O are equivalent to 1 g of Na^S.) PAPER TESTING METHODS 37 b. Dilute 1 cc. of solution (a) to 1 liter to make a 0.001 per cent 'Na = S solution. c. Dilute 10 cc. of solution (b) to 100 cc. to make a 0.0001 per cent XaS solution. Saturate the filter paper in solution (b) and (c) and dry in air. Considerable quantities of these papers may be made at one time and stored in separate, tightly stoppered bottles labeled : "0.001 per cent Na,S paper for tarnishing test." "0.0001 per cent Na 2 S paper for tarnishing test." The papers may also be torn into four equal segments, each segment (0.1S gram) being sufficient for one test. Materials Required ( 1 ) Four 500-cc. flat bottom flasks, approxi- mately 7 inches high; (2) Granulated zinc (arsenic free); (3) 15 per cent HC1 solution; (4) Lead acetate test paper, moistened; (5) Absorbent cotton. Method Into each flask put 2 grams of granulated zinc and 0.15 gram of paper torn into small pieces. The four flasks are for the following papers: (1) Sample; (2) Pure filter paper (for a "blank"); (3) 0.001 per cent Na 2 S paper; and (4) 0.0001 per cent Na,S paper. Add to each flash 25 cc. of 15 per cent HC1 (free from As). Into the neck of the flask insert a loose plug of cotton to a depth of about 1.5 in. Above the cotton place a piece of moistened lead acetate test paper about one inch square, and cover this loosely with a plug of cotton. Set the four flasks in a pan. or tub contain- ing water at room temperature to a depth of 025-0.50 inch, or in order to prevent any considerable rise of temperature of the con- tents of the flask. The liberated hydrogen will carry any H.S evolved up to the lead acetate paper, which will darken. Examine the four lead acetate papers at the end of 30, 60 and 90 minutes and record their comparative appearances. ^Interpretation of Results It has been found that the O.C01 per cent NaS paper causes some tarnishing when held in contact with a polished 10 cent piece for five weeks. Commercial papers known to have caused tarnishing of polished metal goods have been found to lie more reactive under this test than the 0.001 per cent Na 2 S paper. Therefore, a paper to be acceptable should show up as well as the 0.0001 per cent Na.S paper (which should show slight discoloration in about sixty minutes). A paper between 0.0001 per cent and 0.031 per cent Na^.S papers is dangerous ; while those that are inferior to 0.001 per cent Na,S paper should be unques- tionably rejected. In reporting, a paper superior to 0.0001 per cent Na 2 S paper 'honld be classed as "safe"; those between 0.0001 -per cent and 0.001 per cent Na.S as "questionable" ; and those inferior to 0.001 per cent Na 2 S as "unsafe." Note *The practical use of paper for wrapping polished metal seems to in- dicate that sulphur in forms other than sodium sulphide will produce a tarnish- ing effect. This subject should be investigated before the method is adopted generally. V. INTERPRETATION OF DATA The technique of paper testing has developed in no orderly or systematic manner and, in nearly all cases where paper is being tested, the methods are used chiefly for mill control purposes. In sucli cases, comparative results only are necessary and few attempts have been made to interpret the data obtained in any fundamental units. Little attention has been given the calibration of testing instruments or the experimental error of the methods. Provision for the proper error of sampling and testing is generally overlooked and considerable friction has at times developed for these reasons. 1. Relation of Various Tests Some attempts have been made to draw a relation between some of the physical qualities of paper, with especial reference to burst- ing, folding, tearing, anil breaking strength. Although there is a wealth of such data available, both published and in laboratory files, the only conclusions so far reached are entirely negative. In a given paper, it is quits possible to have a strong bursting strength but a weak tearing and folding strength and vice versa. It is interesting to note, however, that both the bursting and break- ing strength are similarly affected by relative humidity, i. e., a maximum strength occurs at about 35 per cent relative humidity. The amount of rosin, glue or starch present in a paper does not seem to have any relation to sizing quality, except in a very general way. It is recommended that this question of the relation of various tests be studied. 2. Quality Indicated by Tests It is quite general practice to make certain tests on paper whether or not the test indicates the quality in question. This has been due to lack of test methods to some extent but discrimifiation should be exercised in the choice of the proper test. Folding endurance seems to be the best method of determining the durability and probable life of a paper, while the bursting strength is so affected by various factors that the data obtained with it are often misleading. It is recommended that data be collected and sug- gestions made as to the proper tests for various kinds of paper. 38 PAPER TESTING METHODS VI. BIBLIOGRAPHY 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39 40. 41. 42. partial list of reference books and articles in periodicals 1. Books The Chemistry of Paper Making, by R. B. Griffin and A. D. Little. Chap. 9, pp. 400-451. Allen's Commercial Organic Chemistry. Vol. 1, pp. 465-480. Chemistry of Pulp & Paper Making, by Edwin Sutermeister. Chap. 15, pp. 386-428. Elementary Manual of Paper Technology, by R. W. Sindall. Chaps. 9, 10, 11. 12, pp. 107-213. Engineering Chemistry, by T. B. Stillman. Fifth edition, pp. 561-568. Ilandbuch der Papierkunde (Hand-book of paper technology), by Paul Klemm, pp. 248-327. Modern Pulp and Paper Making, by G. S. Witham, Sr. Chap. 17, pp. 462-500. Paper and Its Constituents, by H. A. Bromley. Part III, pp. 141-212. Paper, Its History, Source and Manufacture, by H'. A. Maddox. Papier priifung (Paper Testing), by Wilhelm Herzberg. Technical Methods of Analysis, by R. C. Griffin, pp. 337-363. A Text Book of Paper-Making, by C. F. Cress and E. J. Sevan. Chap. 14, pp. 371-402. 2. Articles Absorbency of Paper, by E. O. Reed. Paper, Vol. 21, No. 19, p. 14. J'an. 16, 1918; Jour. Ind. & Engr. Chan., Vol. 10, p. 44, Jan. 1918 Absorption Power of Paper Testing. Paper, Vol. 29, No. 22, p. 12, Feb. 1, 1922. Alum in Paper, Test for. World's Paper Trade Review, Vol. 75, p. 12. Animal Size in Paper. Pafer Makers' Monthly Jour., Nov. 15, 1919; Paper, Vol. 25, p. 622 (1919). Asbestos Paper, Estimation of. Pafer, Vol. 23, folio p. 117, Oct. 9, 1918. Ash Content of Paper, by Hans Wrede. Paper, Vol. 6, No. 7, p. 13, Jan. 31, 1912. Ash Tests and Their Significance, by F. E. Plumstead, Pulp and Paper Magazine of Canada, Vol. 14, No. 2, p. 31, Jan. 15, 1916, Paper, Vol. 17, No. 20, p. 16, Jan. 26, 1916. Bag Paper Testing Lime and Cement, by P. L. Houston Tech. Papers No. 187, Bureau of Standards; Pulp cr Paper Magazine of Canada, Vol. 18, p. 947, Sept. 9, 1920; Paper, Vol. 27, p. 15, Sept. 22, 1920. Balance Pocket Quadrant Demy. Paper Makers' Monthly Journal, Vol. 59, p. 3. Blue and Brown Print Paper, by F. P. Veitch, C. F. Sammet and E. O. Reed, Jovr. Ind. fr Engr. Chem., Vol. 10, p. 222, Mar., 1918. Blotting Paper, The Testing of, by P. L. Houston and R. H. Ledig. PAPER TRADE JOURNAL, Vol. 73, No. 19, p. 88, Nov. 10, 1921. Blotting Paper, Technology of. Paper, Vol. 20, No. 10, p. 16, May 16, 1917. Bulker Measuring by Perkins Pressure. Paper, Vol. 19, No. 4, p. 86, Oct. 4, 1916. Bursting Strength of Paper, Conditions Which Influence the, by D. C. Douty. PAPER TRADE JOURNAL, Vol. 50, No. 6, 271, Feb. 10, 1910. Cardboard, The Testing of for elasticity, rigidity and folding, by R. Isnard. Cham. Abstr., Vol. 15, p. 3205, Sept. 20, 1921; PAPER TRADE JOURNAL, Oct. 20, 1921. Chemical Analysis of Paper, by H. A. Bromley. Paper, Vol. 15, No. 6, p. 17, Oct. 21, 1914. Cigarette Papers, Chemical Analysis of, by Strand Jordan. Jour, of Ind fr Engr. Chem., Vol. 8, No. 9, p. 812, Sept., 1916; Paper, Vol. 19, No. 10, p. 13, Nov. 15, 1916. Coated Papers & Their Constituents, The Manufacture & Technical Examination of, by H. A. Bromley. Pulp and Paper Mag. of Can. Vol. 13, No. 17, p. 463, Sept. 1, 1915. Color, The Measurement of, by C. E. K. Mees, Jour. Ind. cr Engr. Chem., Vol. 13, No. 8, p. 729, Aug., 1921. Color Measurements. PAPER TRADE JOURNAL, July 8, 1920, p. 58. Color A Means of Accurately Matching (Ives Tint-Photometer), by Otto Kress and G. C. McNaughton. Paper, Vol. 18, No. 21, p. 13, Aug. 2, 1916. Color System, An Examination of the Munsell, by I. G. Priest. Tech- nologic Papers, No. 167, of Bureau Standards. > Dirt in Paper, Identifying, by D. M. McNeale. Paper, Vol. 24, folio p. 1058, Aug. 20, 1919. Expansion of Paper, Relation of Moisture and Paper, by E. Suter- meister. PAPER TRADE JOURNAL, Vol. 59, No. 27, p. 44, Dec. 31, 1914. Fiber Analysis, Microscopic Paper, by G. K. Spence and J. M. Knuiss. Paper, Vol. 20, No. 11, p. 11, May 23, 1917. Fiber Analysis, Paper. Paper, Vol. 17, No. 3, p. 19, Sept. 29, 1915. Fiber Board, Effect of Varying Humidities, by Otto Kress and G. C. McNaughton. Paper, Vol. 22, folio p. 251, May 22, 1918. Fiter Board, Impact Test for, by E. O. Reed and F. P. Veitch. Paper, Vol. 24, folio p. 923, July 30, 1919. Fiber Length and Position, by W. Codlitz. PAPER TRADE JOURNAL, Vol. 72, No. 1, p. 56, Jan. 6, 1921. Fibers as Related to Pulp and Paper, Structure of Wood and Sc.me Other, by H. N. Lee. Pulp and Paper Magazine of Can., \ ol. 13, No. 13, p. 361, July 1, 1915. Fibers. The Characteristics of, by H. A. Maddox. Pulp and Paper Mag. of Can., Vol. 13, No. 21, p. 551, Nov. 1, 1915. 44. Fibers, Differentiation of Jute, Manila and Adansonia. Paper Makers' Monthly Jour., Vol. 57, No. 12, p. 367, Dec. 15, 1919. 45. Fibers, The Length of Some Paper Making, by E. Sutermeister. Pulp and Paper Magazine of Canada, Vol. 12, No. 2, p. 43, Jan. 15, 1914. 46. Fibers, Factors in the Measurement of Pulp, by J. H. Graff and Marie Hodgdon. Paper, Vol. 23, folio p. 333, Dec. 4, 1918. 47. Fibers, Length of Wood, Paper, Vol. 26, folio p. 15, Mar. 10, 1920. 48. Fibers in Paper, Estimating Percentages, R. C. Griffin. Jour. Ind. & Engr. Chem., Vol. 11, No. 10, p. 968, Oct., 1919; Paper, Vol. 25, folio, p. 463, Nov. 5, 1919. 49. Filter Paper, Testing. Zcll staff u. Papier. Vol. No. 1. p. 61, May, 1921. 50. Filter Paper, The Penetrability of, by R. C. Griffin and H. C. Parish. Jour, of Ind. cr Engr. Chem., Vol. 14, No. 3, p. 199, Mar., 1922. 51. Filter Paper, Nctes on the Testing of, by J. Rigand-Monin. Papeterie, Vol. 42, No. , p. 818 (1920). 52. Folding, Resistance to, by W. Herzberg. Chemical Abstracts, Vol 14, p. 2262, July 20, 1920. 53. Folding Endurance of Paper, by F. P. Veitch, C. F. Sammet and E. O Reed. Paper, Vol. 20, No. 12, p. 13, May 30, 1917. 54. Gelatin and Casein. Papeterie, Vol. 42, p. 122, Feb. 10, 1920. 5.i. Glarimeter, by Kieser. Zrllstofi u. Papier, Vol. 1, i>. 113, July, 1921. 56. Glarimeter, Instrument for Measuring the Glaze of Paper. Electrical World Vol. 63, p. 645, Mar. 21, 1914; Pulp S- Paper Mag of Can., Vol. 12, p. 233, Apr. 15, 1914. 57. Glarimeter, Improved, by L. K. Ingersnll. Paper, Vol. 27, No. 23, p. 18, Feb. 9, 1921. 58. Gloss of Photographic Paper, Measuring the. Paper, Vol. 26, folio p. 782, May 26, 1920. 59. Graphic Analytical Method for Paper, by O. L. Gartland. Paper, Vol. 25, folio p. 515, Nov. 12, 1919. 60. Groundwocd, Phenylhydrazine Test for. Paper Vol. 23 folio p. 31, Sept. 18, 1918. 61. Humidity Affects Paper, How, by H. A. Maddox. Paper, Vol. 7, No. .22, p. 4 (1911). 62. Humidity, How Paper Is Affected by, by Otto Kress and Philip Silver- stein. Paper, Vol. 19, No. 25, p. 13, Feb. 28, 1917. 63. Humidity, Physical Testing of Papeir as Affected by, by Ross Campbell Jour. Ind. & Engr. Chem., Vol. 9, p. 658, July, 1917. 64. Humidity on the Moisture O ntent of Paper. The Effect of, by Ross Campbell. PAPER TRADE JOURNAL, Vol. 73, No. 2, p. 30 (1921). 65. Humidity on the Strength of Paper, Effect of Papeterie, Vol. 41 p 455, Oct. 25, 1919. 66. Humidity Testing Room, Description of a Constant Temperature and, by F. P. Veitch and E. O. Reed. Paper, Vol. 21, No. 23, p. 174, Feb. 13, 1918; Jour, of Ind. cr Engr. Chem., Vol. 10, p. 38, Jan., 1918. 67. Iron Impurities in Paper, by H. A. Maddcx. Pulp cr Paper Mag. of Can., May 1, 1914. 68. Laboratory, Notes on the Design and Equipment of a Paper and Pulp Mill, by "Snow-Shoe." Pulp fr Paper Mag. of Can., Oct. 1, 1915. 69. Loading and Filling Materials, by Sindall & Bacon. Paper Makers' Monthly Journal; Paper, Vol. 20, No. 7, p. 22, Apr. 25, 1917. 70. Loading of Paper, Qualitative Determination of the. La Papeterie, Vol. 41, p. 266, Aug. 25, 1919. 71. Microscope, The Use and Care of the, by E. Sutermeister. Pulp fr Paper Mag. of Can., Vol. 13, No.' 22, p. 576, Nov. 15, 1915. 72. Microscopic Analysis of Fibers, Modification of Iodine-sulphuric Acid Stain. Paper, Vol. 24, folio p. 707, July 9, 1919. 73. Microscopical Analysis of Fibers. La Papeterie Vol. 41, No. 1, p 30, May 25, 1919. 74. Microscopical Characteristics of Rosin, by James Scott. The Paper Makers, Vol. 49, No. 6, p. 671, June, 1915; Paper, Vol. 16, No. 18, p. 13, July 14, 1915. 75. Microscopical Examination of Paper Fibers. Paper, Vol. 29, No. 9, p. 25, Nov. 2, 1921. 76. Microscopical Work in Paper Testing, by E. M. Chatnot. Jour of Ind fr Engr. Chem., Vol. 10, No. 1, p. 60, Jan., 1918; Paper, Vol. 21, No. 19, p. 17. Jan. 16, 1918. 77. Microscopy, Iodine Solution in Paper, by C. J. West. PAPER TRADE JOURNAL, Vol. 73, No. 4, Aug. 4, 1921. 78. Microscopy of Paper Fiber (C. G. Bright Stains). Paper, Vol. 20, No. 25, p. 11, Aug. 29, 1917. 79. Microscopy of Parchment Paper, by C. Bavtsch. Pupier-l-ahrikuiit Yul. 16, p. 171 (1918). 80'. Microscopy of Pulpwoods, by Eloise Gerry. Paper, Vol. 26, folio n. 277, Apr. 21, 1920. 81. Mineral Matter of Paper, Analysis of, by J. Scott. Paper Maker & British Paper Trade Journal, Vol. t>l. No. 4. 82. Moisture on Paper Tests, Influence of. Paper Makers' Mi uthlv U'unnif, Vol. 60, No. 1, p. 25, Jan. 16. 1922. 83. Moisture on Paper, Effect of, Paper Makers' Monthly Journal, Vol. 57, p. 231, Aug. 15, 1919. 84. Moisture on Paper Tests, Influence of. Paper, Vol. 29, No. 4, p. 16, Dec. 7. 1921. 85. Moisture Regain of Papers at Different Humidities, liy Otto Kress and G. C. McNaughtr.n. Paper. Vol. 22, folio p. 665, Aug. 21. 1918. 86. Capacity, Factors in Obtaining. PAPER TRADE JOURNAL. July 29, 1920. "87. Paper Microscopy, by J. H. Graff. Paper, Vol. 23, folio p. 642, Feb. 12, 1919. 88. Paper Sizing, by Fritz Stockigt. Wochenblatt fur Papicrfahrikation, Vol. 1, p. 39 (1920); Paper, Vol. 26, folio p. Mar. 1O, 1920. 89. Paper Testers, by D. ( Douty. PAPER TRADE JOURNAL, Vol. (HI, \o. 6, p. 259, Feb. 10, 1910. PAPER TESTING METHODS 39 90. Paper Teeing. World's Paper Trade Re-.'ieu; Vol. 74, p. 26, Dec. 24, 1920. 91. Paper Testing, by F. A. Curtis, Circular No. 107, Bureau of Standards. 92. Paper Testing, Report of Committee of Tappi, by F. C. Clark. I'apcr, Vol. 21, No. 6, p. 11, Oct. 17, 1917; Paper, Vol. 21, No. 7; p. 11, Oct. 24, 1917. 93. Paper Testing, TAPPI Report on, by F. C. Clark. Paper. Vol. 25, folio p. 693, Dec. 10, 1919; Dec. 17, 1919; Dec. 24, 1919; Dec. 31, 1919; Jan. 7, 1920. 94. Paper Testing, The Technique of, by II. A. Bromley. Pulp & Paper Mag. of Can., Vol. U, No. 16, p. 439, Aug. 15, 1915. 95. Phlorcgiucinol, Notes i.n the Chemistry of. Paper, Vol. 22, folio p. 641. Aug. 14, 1918. 96. Photomicrographic Study of Paper, by E. A. Hunger. Paper, Vol. 20, Xo. 19, p. 14, July 18, 1917. 97. Porosity of Papers, Determining the. Paper, Vol 22, folio p. 91, Apr. 10, 1918. 98. Porosity of Paper, Method of Testing Relative, by F. J. Seiter. Paper, Vol. 21, No. 2, p. 17, Sept. 19. 1917. 99. Pulps in Paper. Method for Differentiating and Estimating Unbleached Sulphite and Sulphate, by R. E. Lofton and M. F. Merritt. Tech. Papers, 189, "Bureau of Standards. 100. Qualities and Tests of Paper. La Papclcric, Aug. 10, 1919; Paper, Vol. 25, folio I>. 1112, Feb. 11, 1920. 101. Qualities and Tests of Paper. La Papeterie, Vol. 41, p. 98, June 25, 1919. Vol. 41, p. 226, Aug. 10, 1919; Paper, Vol. ,25, p. 1114 (1920). 102. Quality of Paper, Methods of Estimating the, by F. C. Clark. Paper, Vol. 10, No. /, p. 15, Jan. 29, 1913. 1 o.i Kt'sin in Paper, Quantitative Determination of, by C. F. Sammet. Jour, hid. & Engr. Chem., Vol. 5, p. 732, Sept., 1913; Paper, Vol. 13, No. 1, p. 17, Sept. 17, 1913. 104. Rosin Sizing, An Investigation of, by F. C. Clark and A. G. Durgin. Paper, Vol. 21, No. 23, p. 136, Feb. 13, 1918. 105. Size-Fastness, A New Test for, by Stanley A. OkeJl. Paper, Vol. 20, No. 5, p. 20, Apr. 11, 1917. 106. Size-Fastness, Okell's Method for, by S. A. Okell. Paper. Vol. 22, folio p. 469, July 3, 1918. 107. Size-Fastness of Paper, Xew Method for Determining the. by Fritz Stockigt. H'ochenblatt fur Papier-fabrikation (1920); Paper, Vol. 26, p. 1 (1920). 108. Sizing, A New Test for, by C. J. West. PAPER TRADE JOURNAL, June 24. 1920. 109. Sizing with Iodine, Testing, for. Jour, of Ind, & Engr. Chem. Vol. 11, p. 972 (1919). 110. Sizing in High Grade Papers, Detection of Faulty, by C. F. Sammet. Circular No. 107, Bur. of Chemistry, Dept. of Agr.; Paper, Vol. 10. No. 9, p. 15, Feb. 12, 1913. 111. Sizing of Paper, Research Work on the, by F. C. Clark and A. G. Durgin; Paper, Vol. 22, folio p. 223, May 15, 1918. 112. Sizing Quality, The Determination of, by F. T. Carson. PAPER TRADE JOURNAL, Vol. 74, No. 14, Apr. 6, 1922. IK 1 . Soda and Sulphite. Pulp*, Differentiation of, by P. Klemm. Wochschr., Papier-fabrikant. Vol. 48. No. , p. 2159. 114. Soda and Sulphite Wood Pulps in Paper, Detection of, by R. Wasicky. Papier- fabnkaut, Vol. 16, p. 212 (1918); Jour. Soc. Chem. Ind., Vol. 38. ( 115. Spots in Paper, Soot nr Carbnn. Paper, Vol. 17, No. 15, p. 15, Dec. 2-'. 1915. 116. Staining of Wood Fibers for Permanent Microscopic Mounts, by H N. Lee. Pulp & Paper Mag. of Can., Feb. 1, 1917. 117. Starches Properties Useful to Mills, by G. M. MacNider. Paper, Vol. 20, No. 1, p. 16, Mar. 14, 1917. 118. Starch in Presence of Cellulose, Determination of, by F. Kaulfersch. '. him e ct Industrie. May, 1921. 119. Starch in Paj>er, Estimation of, by O. Kamm and F. H. Tendick. Paper Vol. 25, folio p. 460, Nov. 5, 1919. 120. Starch in Paper, Quantitative Estimation of, by V. Voorhees and O. Kamm. Paper, Vol. 24, folio p. 1091, Aug. 27, 1919. by H. N. 123. 124. 125. 126. 127. 128. 129. 130. 131. 132 133. 134. 135. 136. 137. 138. 139. 140. 141. 142. 143. 144. 145. 146. 147. 148. 149. 150. 151. 152. Staining of Wood Fibers for Permanent Microscopic Mounts, Lee. Bctanic'al Gazelle, Vol. 62, No. 4, p. 318, Oct., 1916. Strength of Paper When Wet, Determining the, by E. O. Reed. Journal Ind. & Engr. Chem., Vol. 8, No. , p. 1003, Nov., 1916; Paper, Vol. 19, No. 11, p. 15, Nov. 22, 1916. Strength Tests for Paper, Description of a Paper Tearing Resistance Tester, by H. N. Case. Jour, of Ind. & Engr. Chem., Vol. 11, No. I, p. 49, Jan., 1919; Paper, Vol. 23, folio p. 509, Jan. 15, 1919. Sulphite and Soda Pulp in Paper, Test for. Paper, Vol. 24, folio p. 317, May 7, 1919. Sulphite and Sulphate Cellulcse in Paper, Testing Methods for, by C. G. Schwalhe. Pulp fr Pn*er Max. of Can., Vol. 12, Nc, 1, pp. II, 21, Jan. 1, 1914. Sulphite Pulps. The Differentiation of, by T. B. Seibert and J. E. Minor. Paper, Vol. 25, folio p. 1005, Jan. 28, 1920. Sulphur in Paper, Determination of, by E. Sutermeister. Pulp & Paper Mag. of Can. Vol. 15, No. 44, p. 1021, Nov. 1, 1917. Tearing Resistance of Paper, Te ting, by C. F. Sammet. Paper, Vol. 25, folio p. 1053, Feb. 4, 1920. Tearing Resistance of Paper, by S. D. Wells. Paper, Vol. 23, folio p. 750, Feb. 12, 1919. Tearing Resistance Tester, A Paper, by H. N. Case. Jour, of Ind. cr Engr. Chem.. Vol. 11, p. 49 (1919). Tearing Strength of Paper, Supplementary Study of Commercial In- struments for Determining, by P. L. Houston. PAPER TRADE JbuRNAL, Vol. 74, No. 1O, p. 43, Mar. 9, 1922. Tearing Strength of Paper. World's Paper Trade Review, Vol. 75, p. 6. Tearing Strength of Paper, Device for Testing the (U. S. Pat. No. 1,273,972), by R. O. Wood, to A. D. Little, Inc. Jour. Soc. Chem. Ind.. Vol. 37, No. 21 (1918). Tearing Strength Test for Paper, by A. Elmendorf. Paper, Vol. 26, folio p. 302, Apr. 21, 1920. Tensile Strength Tester (T. J. Marshall & Co.). World's Paper Trade Rez'ie-u.', Vcl. 75, No. 5, p. 468. Tearing Test, Preliminary Study of Tearing and Tearing Test Methods for Paper Testing, by P. L. Houston. Tech. Papers, No. 194, Bureau of Standards. Testing of Paper and Paper Products for Specific Use, by J. D. Mal- colmson, The Paper Industry, Vol. 1, No. 2, p. 104, May, 1919. Testing Physical Properties, by S. W. Widney. The Paper Industry, Vol. 1, No. 7, p. 514, Oct., 1919. Translucent Effect on Paper. Photometric Experiments of the. Jour. of Ind. & Engr. Chem.. Vol. 9, No. , p. 184, Aug., 1917. Translucency and Opacity of Paper, Measuring the, by R. Fournier. Papier, Vol. 23, p. 259, Nov., 1920. Translucency of Papers, A Measurement of the, by C. F. Sammet, Circ. No. 96, liur. Chem., Dept. of Agri.; Paper, Vol. 7, No. 7, p. 22, May 1, 1912. Transparency of Paper and Tracing Cloth, Specifications of the. Circu- lar No. 63, Bureau of Standards. Vegetable Fibers Used in Paper Making, by F. C. Clark. Paper, Vol. 23, folio p. 944, Feb. 26, 1919. Volumetric Estimation of Paper, by E. H. Hiarne, Papier-fabrikant, Vol. 13, No. 45, p. 709, Nov. 5, 1915; Paper, Vol. 17, No. 20, p. 14, Jan. 26, 1916. Water Resistance of Fabrics, by F. P. Veitch and T. D. Jarrell. Jour. Ind. & Engr. Chem., Vol. 12, p. 26 (1920). Webb Paper Tester, by J. D. Malcolmson. Paper, Vol. 23, folio p. 976, Mar. 5, 1919; Jour. Ind. fr Engr. Chem., Vol. 11, p. 133 (1919). Weight of Paper, Determination of the Apparent and Actual Unit. Papier-fabrikant, Vol. 17, p. 472 (1919). Witham Paper Tester. Paper, Vol. 24, folio p. 156, Apr. 9, 1919. Wool, Test for, by H. LeB. Gray, Jour. Ind. & Engr. Chem., Vo. 10, p. 633 (1918). Yellowing of Paper. Paper, Vol. 22, folio p. 1, Mar. 13, 1918. Yell< winp of Paper, by A. P. Hitchins. Paper, Vol. 22, folio p. 553, July 24, 1918. Zinc-Chloride-Iodine Reagent and Its Uses, by F. C. Clark. Paper, Vol. 7, No. 5, p. 23, Apr. 17, 1912. Page A Absorption Test 25 Acid in Paper 36 Air Volume of Paper 29 Alcohol-Ether Method 33 Alum Spots in Paper 16 Analysis, Chemical 31 Analysis, Microscopical 7 Aniline Sulphate Stain 13 Anti-Tarnish Papers 35, 36 Area of Sample 19 Articles in Magazines 38 Artificial Illumination 11 Asbestine '. . . 32 Ashcroft Tester 22 Ash Determination 31 B . Balances 20 Beater Starch 35 Beating, Degree of 16 Bibliography 38 Blanc Fixe 32 Blotting and Fillers 26 Blotting Paper 25 Blotting Test 26 Books 38 Breaking Strength 23 Breaking Strength and Relative Humid- ity 19 Bright Stain 13 Bulk 21 Bursting Strength 20 Bursting Strength and Relative Humid- ity '..... 18 Bursting Testers, Comparison 20 Button Specks in Paper 16 C Calibration of Folding Tester 22 Carbolic Aoid in Paper 36 Cards, Record 7 Case Tearing Test 27 Casein in Paper 33 C. G. Bright Stain 13 'Characteristics of Fibers 14 Characteristics of Paper 19 Chart of Paper Tests 8 Chlorine in Paper 35 Chrome Yellow 36 Classification of Fibers . . .- 13 Coal Particles in Paper 16 Coating, Amount of 32 Coloring Matter 36 Color Spots in Paper 16 Common Stains 11 Compactness, Relative 21 Comparison of Bursting Testers 20 Composition, Volumetric 29 Conducting Particles 30 Conductivity Method '. 28 Container Board, Tester for 22 Contrast Ratio 26 Conversion Factors 20 Conversion to Metric System 20 Count Method 11- Cross Direction 19 Crown Filler 32 D Degree of Beating 16 Degree of Sizing . .. 27 Development of Paper Testing 6 Dextrine '35 Dirt in Paper 16 Drag Spots in Paper 16 Dunlop Method for Paraffin 32 E Electrolytic Method 28 Elmendorf Tearing Test 27 Elongation, at Rupture 25 Estimation of Fiber Content 7, 11 F Factors, Conversion 20 Fats in Paper . 36 Felt Side 19 INDEX Page Ferric Ferricyanide 13 Fiber Analysis 7 Fiber Examination 7 Fiber Weight Length Method 7, '. Fibers, Characteristics of 14 Fibers, Classification of 13 Filler Retention 30 Fillers, Determination of 32 Fillers and Blotting 26 Finish, Measurement of 28 Flotation Method 27 Foam Spots in Paper 16 Folding Endurance 21 Folding Endurance and Relative Humid- ity 19, 22 Folding Factor 22 Free Acid in Paper , 36 Fuchsine . . ' 12 Glarimeter Principle 29,- 30 Gloss, Measurement of 28 Glue and Casein 33 Green Folding Tester T 23 Groups of Test Methods 7 H Herzberg Stain 11 Humidity, Effect of 17 Ingersoll Glarimeter 28 Ink, Standard, for Absorption Test .... 25 Interpretation of Data 37 Iron Specks in Paper 16 J Jenk's Stain 11 K Kamm and Tendick 35 Kamm and Voorhees Method 34 Klemm Test 26 Knife Edge Test 27 Knots in Paper 16 L Little Tearing Test 27 Loading, Retention of 29 Lofton-Merritt Stain 12 M Machine Direction 19 Magazine Articles 38 Malachite Gr.een 12 Manipulation of Fiber Examination. ... 10 Merritt Sulphate Stain 12 Metric, Factor for Conversion of Weight 20 Microscope Magnification 11 Microscopic Analysis 7 Moisture and Relative Humidity 18 Mullen Tester 50 N Nitrogen Determination 34 O Ochres 36 Oil 36 Oil Specks in Paper 16 Okell Method 27 Opacity Apparatus 26 Opacity Test . . '. 26 Paper Characteristics 19 Paper Specks 16 Paper for Electrical Equipment 30 Paper Tests, Chart of 8 Paraffin 32, 36 Para-Nitro-Aniline Stain 13 Particles, Conducting 30 Pearl Hardening 32 Penetration, Water 30 Phloroglucinol Stain 12 Photometer, Martins-Koenig 29 Photomicrographs 28, 35 Physical Testing 17 Pigments, Natural 36 Pipette Test 25 Page Polarimetric Method 35 Preparation of Slide 7 Prussian Blue 36 Raspail Reaction 33 Ratio Bursting Strength to Weight 21 Ream, Standard 19 Relative Humidity, Effect of 17, 22 Resistance to Water Penetration 30 Retention of Loading 29 Roll Lengths 20 Rosin 33 Rosin Extraction Apparatus 33 Rosin Specks in Paper 16 Rubber in Paper 16 S Salicylic Acid 36 Sammet Method 33 Sample Area 19 Sample, Test 7 Sampling 7 Scales 20 Schopper Tearing Tester 27 Schopper Tensile Tester 24 Shaker, Test Tube 10 Sizing, Degree of, Test Methods of De- termining 27 Sizing Materials 33 Sizing Quality 27 Slide, Preparation of 7 Slide Holder 11 Smalts 36 Special Materials, Tests for 36 Special Stains 12 Specks in Paper 16 Spence and Krauss Method 11 Stains, Common 11 Stains, Special 12 Starch 16, 34, 35 Stockigt Method 28, 31 ' Strength Ratio 20 Stress-Strain Tester 25" Strip Test 25 Substance Number 20 Sulphate Stain 12 Sulphur in Paper 35 Sutermeister's Stain 12 Talc 32 Tarnishing Test 36 Tearing Strength and Relative Humidity .19, 27 Tearing Tests 26 Tensile Strength 23 Tensile Strength and Relative Humidity 19 Tensile Tester 24 Testing, Chemical 31 Testing Microscopical 7 Testing, Physical 17 Thickness Tester 21 Thickness Tester Variation 21 Tissue Paper, Anti-Tarnish 35 Tolerances 7 Trade Size, Weight in 20 Trans'lucency ' 26" Transparency . 26 U Ultramarine 36 Unbleached Pulp Stain 13 Volumetric Composition 29 W Warren, S. D., & Co. Retention For- mula 30 Water Penetration 30 Webb Tester for Container Board 22 Weight 19 Weight and Relative Humidity 18 Wet Tensile Strength 24 Wire Side 19 Witham Tearing Tester 27 Wood Specks in Paper 16 Publications of the Technical Association of the Pulp and Paper Industry 18 East Forty-first Street, New York, N. Y. Technical Association Papers, Series III, 1920. In paper, 60 pages, $2. Tests for Unbleached Sulphite and Sulphate Fibers, by R. E. Lofton and M. F. Merritt. Standard Specifications for Cement and Lime Paper Bags, by Paul L. Houston. Use of Sulphur in Soda Pulp Cooking, by ( iec >rge K. S pence. Substitutes for Alum and Rosin, by VV. K. Byron Baker Substitutes for Alum in Papermaking, by Max Cline. Automatic Cooking Control lor Chemical Pulp, by C. H. Allen. Automatic. Mixing System for Paper Stock, by Edward J. Trimbey. A New Felt Cleaning Device, by C. A. Woodcock. Fireproof Hood for Paper Machines, by F. M. Williams. Description of Emmet's Mercury-Vapor Boiler. Technical Association Papers, Series IV, 1921. In paper, 129 pages, $3. How to increase the Efficiency of Water Power Plants, by diaries M. Allen. Strength Testing of Soda Pulp, by Ralph Mair and Grellet N. Collins. Steam Economy in Drying on and Driving of Paper Ma- chines, by R. W. Leeper. Burning of Pulverized Fuel in Paper Mill Power Plant Loren L. Hebberd. Shortening Cooking Time by Preliminary Impregnation in the Production of Sulphite Pulp, by Vance I'. Kdwardes. Measuring Moisture of Chips in Williams. Economics of Paper Mill Ki ion, by Stephen A. Staege. The Fulton System for Drying of Paper, by William B. Fulton. A Xew Weightometer for Soft Stock, Chips and Acid, by E. /. Trimbey. The Effect of Variables on Bleaching Efficiency, by George K. S pence. 'Briner Economi/er I'Miig Only Waste Heat for Ventila- tion of Machine Room, by W. H. Howell. Kintnaii Modification of Sulphate Process, by Bror. N. Segerfelt. Manufacture of Ground wood by the Hrtll Process, by W. A. Munro. Evaluation of Lime by Causticizing Test, by Carl Moe. A Simple Moistun iper, by C. B. Whwing. Study of the Casein I Paper, by Clarke Marion. Analytical and 'rthods 01 littee on Stand- ard Methods o Materials, by E. C. Tucker. The Analysis of Sulphite Cooking Acid, by Erik Oman. Control Analyses of Sulphit'- I'rof. Dr. Peter Klason. Technical Association Papers, Series V, 1922. In paper, 170 pages, $3. The Power Plant of the Paper Industry, by A. G. Darling and H. W. Rogers. A System of Records to Maintain I'nitonnity of Basis Weights of Paper, by Parker K. Baird. Hydrating Machinery for th. Mill, b> George L. Bidwell. Modern Lighting for Paper and Pulp Mills, by J. H. Kur- lander. Some Factors Influencing Yield and Strength of Pulp Cooked by the Soda Process, by Martin L. Griffin. The Efficient Production of Mechanical Pulp, by Adolph F. Meyer. Sedimentation Control of Groundvvood, by W. A. Munro. Drying of Paper, by M. B. Littlefield. The Electric Steam Generator, by Horace Drever and Frank Hodson. Recovery and h G ;< K. Six.-'. Relative Efficiency of the Automal 'm- Grinder as Compared with the Pocket Type Grinder, by John J. Stamso Cotton Linter Pulp, by Stewart E. Seaman. Recommended Specifications for Limestone and Lime in the Manufacture of Sulphite Pulp. Analysis of Reclaimed Cooking Acid for Sulphite Mills, by Gosta P. Genberg. Concerning the Analysis of Raw Sulphite Acid, by Dr. Rudolf Sieber. Contribution to the Knowledge nstitution of Spruce Wood Lignin, by Dr. Peter K! i Concerning Ligiiin and Lignin K'. by Dr. Peter Klason. Contributions to a More Exact K> if the Chemical Constitution of Spruce Wood, by Use of the Continuous Centrifugal, by J. R. Kessler and G. \". Collins. The Chemistry of the Sulphite Pr.. R. N. Miller and W. H. Swanson. Report of Committee on Standard Methods of Testing Ma- terials, by N. F. Becker. Color Effect of Rosin S ion on Finished Product, H. Kent. Sulphur in Sulphite Waste Liquor. Barsky. Producing Bleach Liquor with Liquid Chlorine, by S. W. Jacobs and H. P. Wells. The Value of Fuel Economi/ Mill Operation, by George E. Willi. -rry. A Mew Idea in Chip Break Paper Tes" i Paper. t of Relative Humidity and Variation of the Burst- ing Test. ! est. Sizing Quality. Committee on Paper Testing. Standard Methods of Materials: Aluminum Sulphate. u-ii Filler. Lira Dyestuffs : of Auramine. "Pix-r Sul;-' Two-Side Stilbene Yellow. Methods .iifd. Heat : rally Required. Meat Supplied. Graduation of Temperature. Pound- of P.'i *)rying Surface per I I Address the Secretary Technical Association of the Pulp and Paper Industry, 18 East 41st St., New York Publications THE Technical Association Pulp and Paper hdnstry 18 East Forty-first Street, New York Technical Association Papers, Series VI (1923). In paper, 208 pages, $3 A Theoretical Discussion of the Reactions Papermaking: Jessie E. Minor. Anti-Friction Bearings: G. H. Spencer. Bibliogr~~ "~ West ; Chemistt esses: Chemist! and W Discussic Drying J. O. 1 Effect o Tests: Efficienc W. F. Evaporal Lake C( of Manufact Methods of Establishing Wage Rates and De- termining Promotions: H. P. Carrnth. Papers on various subjects: Paper testing; several papers. Reports of committees. Steam Economy in Pulp and Paper Mills: E. P. Gleason. Steam Flowmeters on Sulphite Digesters: W. H. Kraske. Study of Papermaking Materials: A. B. Green. Use of White Water in Mechanical Pulp Mills: W. E. Brawn. Ventilation of Machine Rooms: J. O. Ross. Waste in the Industry. R. B. Wolf and G. D. Bearce. White Water Losses and their Correction. Utilization of Barking Drum Waste. Reduction of Broke Losses. volumes. In cloth, $5 per volume. i:me IV: Preparation of Rag and Other Fibers. Treatment of Waste Papers. Engine Sizing. Loading. Beating and Mixing. Coloring. Paper Machines. Volume V (in preparation) : Tub Sized Papers. Finishing Operations. Coated and Other Treated Papers. Manufacture of Special Papers, Boards, etc. Paper Testing. Mill Organization. General Mill Equipment. Dictionary of Papers, Tables, etc. Paper Testing. Microscopical ;vised 1922). In paper, $3 ang. alysis. Interpretation of Data. Bibliography. Folder for Technical Association Section, 25 cents. Each Folder will accommodate the Section pages for three months. Index to Technical Section, Paper Trade Journal, 10 cents each Address the Secretary Technical Association of the Pulp and Paper Industry, 18 East 41st Street, New York PAMPHLET BINDER Syracuse, N. Y. Stockton, Calif.