I02
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
T h e observations of Sabin, as described in t h e original communication, are, however, much more comprehensive a n d consist essentially in t h e determination of changes in weight which t a k e place over a lengthy period of exposure of oil a n d paint films (up t o 8 months). As such, t h e y have a n enhanced value. In brief, t h e y show t h a t paint films increase in weight t o a maximum value, a n d t h e n slowly decrease, a n d t h a t even after a period of 8 months t h e decrease contipues. R a w linseed oil shows t h e same behavior b u t decreases in weight more rapidly t h a n does t h e oil cont e n t of a n oil paint. Similar observations were made b y t h e Chemical S u b - c o m m i t t e e of t h e Netherlands White Lead Commission, appointed in 1903. These results have certain practical bearings in particular a s showing t h a t t h e oil portion of paints undergoes a slow b u t continuous decomposition on exposure t o air. According t o Sabin, in 2 4 days, films of paints containing Whiting, T e r r a Alba, Silica, Asbestine, Barytes, China Clay, White Lead, or White Zinc show increases in weight of between a b o u t 1 2 a n d 13 per cent, having fallen from maximum values of from 1 3 t o 16 per cent. T h e following table from t h e report of t h e Netherlands Commission shows t h e changes in weight (decreases) in percentages expressed on t h e original layer of d r y paint. Mica plates covered with paint were placed o u t of doors after having become dry. Duration of Exposure in D a y s NAME O F P A I N T 20 Whitelead.. . . . . . . . 2.8 Zinc white. . . . . . . . . . 2 . 9 Lithopone. . . . . . . . . . .
40
60
80
. . . . . 4.0 . . . . . . ... . . . . . . 8.6
120 4.1
2 1. 2 35.8
200
230
60.8
83.9
.. .. .. .. .. .. .. ..
These results show t h a t white lead paint loses much less o n exposure t o t h e air t h a n zinc white or lithopone, a n d constitute a striking refutation of t h e last sentence of t h e following s t a t e m e n t : “Oxide of zinc is practically without action on linseed oil; therefore, when it is ground in that medium the conditions that obtain cannot be compared with those that exist in the case of white lead. The drying of paint made from oxide of zinc is due entirely t o the siccative nature of the oil itself in which the oxide of zinc may be considered as mechanically suspended. We have here a state of things more readily under control than is the case with white lead paints in which the powerful siccative action of the hydrate portion of the white lead often proceeds too far. The oil is then burnt up so to speak; the paint perishes and ‘chalking’ results.”1 This a n d similar s t a t e m e n t s are used t o decry t h e properties of white lead b y those whose interests lie in t h e sale of other pigments. It is a n open question whether t h e behavior of paint films can be correctly studied b y t h e use of linseed oil a n d pigment alone. I n general, turpentine or a similar volatile thinner is present in paint when technically applied, a n d there is good reason t o believe t h a t such thinners may not be without effect in determining t h e character of t h e oxidation processes, more particularly in so far as t h e volatile products are involved. T h e whole problem of t h e drying of linseed oil alone or when used as a paint medium is one of extreme difficulty, a n d a t t h e present time such information as page 498, “White Paints a n d Painting M a t e 1 From advertisement, rials,’’ Scott, pub, by T h e Modern Painfer, Chicago, 1910, a n d attributed t o J. Cruickshank Smith in a lecture before the Institute of British Decorators.
Vol. 7 , No.
2
is available appears t o be so lacking in agreement, a n d so contradictory, t h a t no t r u e explanation of t h e chemical changes has yet been brought forward, although m a n y theories have been published. T h e formation of volatile products (other t h a n carbon dioxide a n d water) during t h e drying of linseed oil has been known f o r some time, a n d more recently t h e hygienic value of these products has been appreciated. The presence of t h e lower f a t t y acids, aldehydes, etc., has been demonstrated, b u t as yet no detailed examination of t h e products has been carried o u t . This is a problem which few technical chemists have t h e facilities for attacking, a n d t h e y might well engage chemists more conveniently placed who have liquid air a t their disposal. By such condensation a n d collection of these volatile products a t low temperatures a n d their subsequent examination it is highly probable t h a t valuable evidence as t o their chemical constitution would be obtained. T h e course a n d t y p e of oxidation is apparently influenced b y t h e t e m p e r a t u r e a n d this has i m p o r t a n t practical application. T h e great disparity between t h e figures given for increase of weight of films b y different workers indicates t h e difficult nature of t h e inquiry. T h e so-called ( I oxygen absorption values” a s determined b y t h e exposure of films t o air, on open plates or t h e like, cannot claim t o be anything more t h a n empirical values, a n d have a correspondingly reduced scientific interest. I n such methods there is absolute disregard of t h e formation of volatile products, a n d t h e values obtained in no way represent t h e “ t r u e oxygen absorption.’’ T h e investigators who h a v e a t t e m p t e d t o determine t h e t r u e oxygen value have realized t h e complicated character of t h e volatile products, b u t have in nearly every case considered t h a t passage through calcium chloride a n d potash would be sufficient for their retention-a quite unjustifiable assumption in our present state of ignorance a s t o t h e t r u e chemical character of t h e volatile products. These a n d m a n y other problems present themselves in t h e detailed s t u d y of paint, a n d there is a wide field for t h e scientific investigation of t h e chemical changes involved in t h e application a n d use of paints. CHEMICALLABORATORY OF THE BRIMSDOWN LEAD CO.. LTD ENPIELD HIGHWAY,MIDDLESEX,ENGLAND
A STUDY OF VAFUOUS TESTS UPON GLUE, PARTICULARLY THE TENSILE STRENGTH’ B y AucusTus H. GILL Received S o v e m b e r 17, 1914
T h e object of this work was t o compare t h e various tests applied t o determine t h e properties of glue a n d more particularly t o see if t h e y bore a n y relation t o its tensile strength. I-PRELIMIKARY~
TEST-FOllOWing t h e work of F e l ~ ,t h~e viscosity of I j per cent solutions of glue a t 30’ C. were determined with t h e Engler viscosimeter; as t h e VISCOSITY
1 T h e experimental work of this paper was done b y six students, working successively. E a c h worker’s name is given in connection with t h e report of his experiments. 2 B y W. A. Marshall.
a
Chem. Zetf., 21, 56, 70.
T H E J O U R N A L OF I N D C S T R I A L A N D ENGINEERING C H E M I S T R Y
Feb., 1915
results obtained were unsatisfactory, t h e Doolittle viscosimeter was used, employing strengths of glue from 4 t o 2 j per cent. I t was found t h a t there was too little variation in t h e viscosity of solutions of glue of widely varying tensile strengths t o make this method of a n y practical use. J E L L Y T E S T (LIPOWITZ)-7 g. Of glue were dissolved in 96 cc. of water b y allowing i t t o soften for 1 2 hrs. i n t h e water, finally warming t o complete t h e solution on t h e water b a t h . It was t h e n allowed t o cool, finally chilled with ice, t h e jelly broken in t h e machine a n d t h e strength reported i n grams per sq. in. necessary t o break t h e surface. Table I shows t h e results obtained. D E T E R M I X A T I O N OF T H E T E S S I L E S T R E S G T H - I t was supposed t o be a comparatively easy matter t o glue t w o pieces of wood together a n d measure t h e force necessary t o pull t h e m a p a r t . On a more careful consideration i t was found t h a t m a n y factors entered in t o complicate matters a n d render its execution difficult. A cement testing machine was used in these tests, t h e blocks of wood being sawed out t o resemble cement briquettes. These blocks were first made of maple a n d glued together with t h e grain; on subjecting these t o test, t h e wood itself broke rather t h a n t h e g l u e d joint, a t pressures varying from 180 t o 370 lbs. per sq. in. All future experiments were made b y gluing t h e maple blocks together endwise. A 20 per cent solution of glue, made b y dissolving on t h e water bath, was applied evenly t o these end surfaces, of a sq. in. area, subjected b y means of ordinary carpenter’s clamps t o as even a pressure as possible, allowed t o dry for 24 hrs. a n d t h e joint broken. T h e average of three tests each is shown in Table I. T A B L EI-JELLY
STRENGTH TESTSOF HIDE GLUES TEST TEKSILE STRENGTH G per sq in Lbs. per sq. in. Average Range Averace A ....................... 2440 1384-1744 1544 , B ....................... 1969 1402-1 685 1561 c ....................... 1521 91 1-1298 1402 D ....................... 1360 ..... 1282 E ....................... 1200 752- 944 1309 AND
JELLY
The results v a r y quite widely, a n d t o t r y a n d reduce this variation, blocks t h e shape of briquettes were cut with a special moulding cutter across t h e grain of a ;?-in. plank. This gave briquettes 9 or I O in. thick instead of b u t I in., t h e idea being t o use blocks from t h e same piece of wood a n d blocks which h a d been glued under identically t h e same conditions a n d t h e n saw t h e m a p a r t into briquettes having t h e usual square inch section. T h e gluing was effected as before, using. a 2 5 per cent solution of glue a n d t h e blocks were weighted with a 2 0 lb. weight in t h e center, drying t h e m for 24 hrs. or 48. Table I1 shows t h e results of t h e test, t h e arrangement of t h e sections, and t h e length of time of drying of each piece. S T R E S G T H I N LBS. PER SQ. IK. OF GLUE APPLIED THICKBLOCKAFTERWARDS SAWN APART E n d . ..................Center. End
TABLE II-VARYIXG TO A
GLUE
E: Lbs . . . . . . 820 B:
24 Hrs.. . . . . Lbs . . . . . . 1720 Hrs . . . . . . 48
...................
1240 1280 1336 1424 1232 1200 48 48 48 24 24 24 1532 1600 1344 1240 1496 1428 1520 24 48 48 24 24 24 24
1144 48 1708 48
I t will be noticed t h a t with Glue E, t h e joints in t h e center of t h e block are t h e stronger, while t h e reverse
I03
is t h e case with B ; this might have been because t h e glue was thinner a t these places, due t o t h e springing of t h e blocks, b u t i t was hardly thought possible, as they were more t h a n 2 in. deep a n d wide. T o t r y a n d obviate this difficulty, blocks t h e size of a pair of briquettes were used, glued under pressure, a n d then sawn apart. TABLE 111-STRENGTH Glue
IK LBS. PER SQ. I N . OF GLCE APPLIEDTO P A I R S OF BLOCKS
DRIED U N D E R 2 LBS. PRESSURE DRIED WITHOUT PRESSURE A C D E A B C D E B 1347 1553 520 849 1108 1624 1579 1043 1385 1454 588 1463 1543 1521 1420 1164 1463 1842 505 745
- - _ _ _
- - _ - -
Average, 1405
1698
513
797
11-JOINTS
848
1544
1561
1282
1402
1309
A N D SURFACES’
It was found t h a t all of t h e briquettes used in Table I11 were more or less sprung a n d t h a t , being cut against t h e grain, t h e grain of t h e wood was bruised a n d bent down. T h e blocks were re-surfaced by hand, using a sharp plane finely set a n d t h e tests repeated. Results were obtained varying from 262 t o 1490 lbs. per sq. in. Instead of weighting t h e joint when drying, i t was made with carpenters’ clamps, obtaining less widely varying results, i. e., from 5 2 4 t o 1623 lbs. a n d from I 2 I 2 t o 169 j lbs. Obviously the difficulty lay in making t h e joint. Among woodworkers using glue, t h e “rubbed joint” has a reputation for strength, a n d accordingly this was next tried. T h e glue-sized briquettes were covered with a n excess of hot glue a t t h e joint, pressed together t o expel all air bubbles, a n d t h e two surfaces rubbed together until t h e glue became stiff a n d tacky, when t h e pieces were set aside t o dry. On breaking t h e joints, strengths from 760 t o 1960 lbs. per sq. in. were obtained. With t h e weaker, t h e joint was free from holes a n d flaws, b u t appeared glazed, whereas in t h e stronger t h e surface was uniform a n d presented a frost-like appearance. Probably t h e glazed surface represents t h e peeling of t h e glue from t h e wood, whereas t h e frosted shows t h e fracture of t h e glue. I n order t o make t h e surfaces even more perfect, t h e size was removed from used briquettes by allowing t h e m just t o dip in boiling water: on drying, a n even open surface was obtained, which gave t h e glue a chance t o penetrate deeply into t h e wood. Rubbed joints were made, using these pieces, a n d results from 1248 t o 1986 lbs. per sq. in. obtained. As with a cement briquette placed b u t 1/16 in. off center, a difference in strength of 33 per cent may be obtained, so i t is possible here t h a t t h e differences may have been due t o a bending moment in t h e test pieces which, however, would appear t o be unavoidable with these briquettes so t h a t t h e results just cited would seem t o be t h e best obtainable b y this method. 111-BRIQUETTES
O F M A T E R I A L S O T H E R T H A N WOOD’
Preliminary experiments were made with rubbed joints using a well known liquid glue, dried without pressure for 38 hrs.; maple briquettes were employed as before. N o difference could apparently be seen between t h e joints, which were about 0 . 0 0 2 in. in thickness. T h e results were 4j0, 574, 748, 776 and 1098 1 2
By A. F. Nathan. By H. B Chalmers.
T H E J O U R N A L OF INDC‘STRIAL A N D E N G I N E E R I N G C H E M I S T R Y
104
lbs. breaking strength per sq. in. The work was repeated using a strong a n d a weak glue. Every a t t e m p t was made t o have t h e results as uniform as possible. T h e briquettes were heated t o 90’ C., t h e glues t o 95’ C. a n d brought t o t h e same consistency; t h e wooden surfaces were given five coats of thin glue sizing, finally glued a n d allowed t o dry under 40 lbs. pressure for 37 hrs. The strong glue gave 5 j 3 , 7 7 7 , 7 8 9 , a n d 1 1 0 7 lbs. a n d t h e weak 3 2 4 , 4 9 4 , 6 j 6 a n d 9 0 3 lbs. T h e test was repeated using a very strong glue: 1 2 3 4 , 1 7 7 6 , 1 8 9 7 , 1 9 2 0 , 2 1 6 8 , 2 2 4 4 , 2393 a n d 2 8 0 0 lbs. breaking strengths were obtained, Finally a n experiment was made as in Table 11, using a thick ( 6 . j i n . ) briquette, glued with t h e liquid glue already mentioned a n d dried for 9 6 hrs. in a testing machine under a load of 4090 lbs.; on being sawn apart, t h e breaking strengths were as follows, arranged in t h e order of t h e sections: 7 2 0 , 804, 1060, 9 5 0 , 742 a n d 5 2 4 lbs., t h e middle ones being t h e strongest. These results being so unsatisfactory, substances other t h a n wood were sought: porcelain lacked in porosity, tiling broke a t 4 0 0 t o joo lbs., while glass, like wood glued with t h e grain, breaks elsewhere t h a n at t h e joint. Weidenbusch, in 1 8 j 9 , used rods of plaster of Paris mixed with glue; t h e method has t h e reputation of being uncertain, owing perhaps t o t h e setting of t h e plaster. Following this example, briquettes of fuller’s earth, diatomaceous earth, quartz sand a n d sawdust were made, using solutions of t h e various glues as binders. These in some cases were dried a t 80’ for 6 days. It was difficult t o d r y t h e m completely, a n d t h e resulting briquettes were full of blow-holes rendering difficult a n accurate measurement of t h e broken area. Some showed little or no strength, while others gave 1 3 2 0 a n d 1480 lbs.; these were reglued a n d t h e fract u r e took place at a new point a t 840 a n d 800 lbs.; on again being reglued t h e y broke in still different places a t 1 2 1 6 a n d 1 2 1 2 lbs. Setterberg’ employed strips of paper dipped in t h e glue solution a n d afterwards dried t o determine t h e strength of glue; this was not found in our hands t o give good results. Instead of finding t h e increase in tensile strength of t h e paper, it was thought t h a t t h e bursting strength as shown b y t h e Mullen paper tester might afford more reliable results. T h e tests were conducted as follows: strips of filter paper 2 in. wide were dipped into 2 j per cent solutions of t h e glue a n d allowed t o dry in t h e air for 36 hrs. T h e TABLE IV-BREAKING STRENGTHS
OF
GLUE O N FILTER PAPER
LSS. PER SQ. IN. PER 100 MGS. OF GLUE
Averaee
B 37.5 38.0 36.6 36.5 36.7 35.9 36.7 34.5 38.6 36.9 35.3 35.0 3 6 . 5
C 26.9 28.7 26.3 26.1 29.8 27.8 27.2 25.0 28.5 27.9 26.1 25.2 2 7 . 1 35.5 36.5 35.2 35.0 35.6 34.7 32.6 33.2 35.1 34.8 34.6 33.5 3 4 . 7 16.9 20.2 20.4 20.0 18.5 19.3 23.6 17.3 19.4 20.1 19.9 20.1 1 9 . 6
D E
paper was c u t into 2-in. squares a n d weighed; these weighed before treatment from 4 9 9 t o 618 mg. a n d carried from 86 t o 195 mg. of glue. T h e y broke a t from 1 7 t o 39 lbs. per sq. in. per 100 mg. of glue upon t h e 4 sq. in. of surface. Table I T shows t h e variations with different glues. The results, while showing nothing as t o t h e actual 1 Schwed.
Tech. S‘idskrzfl, ‘28, 52.
Vol. 7 , NO.
2
tensile strength of t h e glue, readily enable t h e strongest glue t o be selected; furthermore, they are much more concordant t h a n a n y t h a t have so far been obtained. Considering Glue B as 100, t h e other glues rank as shown in Table 1’ b y t h e various tests. TABLEV-COMPARISON OF VARIOCSTESTSU P O N GLUE B C C u p t e s t . . . . . . . . . .. . . . . , 100 68 Viscosity ..... . . . .... . . , . . 100 97 Tensilestrength . . . . ... , . . , 100 40 Sized paper . . . . 100 81
. ....... . . . .
IV-BEARING
THE
DIFFERENT GLUES
D
E
76 99
60 96 60
80 94
61
S U R F A C E S , JOIKTS A N D G L U E S O L U T I O Z J S ~
Careful consideration of t h e causes of error in t h e strength tests with wooden briquettes revealed one which so far had been overlooked. This was t h e bearing surface between the wood a n d t h e bronze clamp of t h e testing machine; if there were inequalities in t h e wood caused by irregularities in t h e grain or t h e hardness of t h e wood, these would produce eccentric loading. T o obviate this i t was proposed t o use round blocks I in. in diameter with lag screws at each end, which could be suitably clamped; t h e lag screws were t o be center-marked on their lieads a n d t h e blocks turned down upon these centers, t h u s ensuring proper alignment. The blocks were t o be sawn a p a r t for gluing. While a inch lag screw required 5800 lbs. t o pull i t out of t h e block, yet i t was found t h a t this procedure was too tedious a n d troublesome. On suggestion of Professor Schwamb, rectangular prismatic blocks were used of t h e dimensions shown in Fig. I-A, a n d sawn a p a r t with a special saw. These were blocked up with bronze blocks t o fit in t h e briquette holder of t h e testing machine. T h e depth of t h e slot was found by determining t h e compression strength of t h e maple (which was 11 5 8 0 lbs. per sq. in.) a n d using a sufficient area t o give a strength of a t least 2 0 0 0 lbs.; this would be about 3/32 in. on each side. T h e method of preparing t h e joint a n d glue was as follows: t h e blocks were placed in a form a n d center punched on t h e ends, two numbers were placed on each for identification of each end a n d t h e block carefully sawn in two. This is one of t h e most important parts of t h e whole operation. The blocks are securely clamped in a “fence” a n d this sets upon t h e “ r e s t ” of t h e saw table; t h e saw used must be carefully trued upon t h e mandrel upon which it fits a n d is frequently filed. The blocks should be sawn a t ‘a definite rate. When done they should fit together perfectly a n d not “rock”-showing inequalities of surface; t h e surfaces should be smooth but not glassy. One hundred a n d twenty grams of glue were weighed o u t into a beaker, covered with 1 5 0 cc. of water, allowed t o soak over night, when i t was warmed t o dissolve t h e softened glue, allowed t o stand again, a n d finally water added t o make t h e weight 3 0 0 g., warmed on the steam-bath t o a temperature not exceeding 6 j 0 a n d stirred until i t was homogeneous. T h u s nearly two days were required t o make t h e glu? solution a n d care was taken t o heat i t neither higher nor longer t h a n necessary since such over-treatment causes a decomposition which diminishes t h e strength of t h e glue. A properly glued joint after breaking 1
By P. A. Esten.
Feb.,
191j
T H E JOGR,VAL O F I , V D C S T R I A L A N D E LVGI N E E RI LVG C H E M I S T R Y
should not show “glazed” spots-places where t h e light is reflected, showing t h a t t h e glue has not filled in t h e space between t h e ends of t h e fibers; t h e broken surface on a strong joint is rough a n d irregular a n d of a frosted appearance. Besides t h e preparation of t h e glue a n d joint, t h e manner in which t h e joint is dried is of importance: this is ordinarily done in practice under pressure of screw clamps. As this pressure is very variable, t h e machine shown in Fig. I - B was devised. This enables a n y pressure up t o IOO lbs. per sq. in. t o be applied. I t consists of a frame carrying a dozen round, pointed steel pins in t h e t o p row: opposite t h e m in t h e b o t t o m row is a n equal number of pointed screws; bent levers, I, I O in. long with j as a fulcrum rest in holes in t h e t o p of t h e pins p , a n d carry a weight of I t o 3 lbs.
still in this holder t h e block was p u t in position in t h e drying machine, t h e weights applied a n d t h e form removed. T h e blocks were kept under a pressure of 31 lbs. for I hr., t h e n heated t o 50’ C. for 3 hrs. a n d dried z or 3 days a t room temperature. T h e results obtained a n d a comparison of t h e various tests made so far are shown in Tables V I a n d V I I . TABLEVI-TESSILE
STRENGTH (LBs. PER SQ. IN.)OF VARIOUSGLUES G l u e s o . 1 . . . . . . . . . . . . . . . . 1594 1627 1729 1820 1905 2081 2 . . . . . . . . . . . . . . . . 1782 1878 1901 1942 1952 1953 2011 3 . . . . . . . . . . . . . . . . 1938 2098 2168 2285 2299 2310 2553 4 . . . . . . . . . . . . . . . . 1358 1495 1573 1658 1762 1809 1927 S . . . . . . . . . . . . . . . . 1582 1635 1755 1878 1963 1993
TABLE\-II-COXPARISON
OF COSITY
TENSILE STRENGTH, JELLY TESTA N D VIS-
OF VARIOUSGLUES, Giue No. 1 2 3 Average 3 highest in Table VI, lbs.. . . . . . . 1935 1982 2387 Jelly test, g r a m s . . . . . . . . . . . . . . . . . . . . . . . 1223 145 358 Viscosity a t 104‘ F grams s u g a r . . . . . . . . . 1 8 . 2 1 3 . 8 1 6 . 2
.
DESCRIPTION
- - 9‘‘-
-
4 1866 171 13.9
5 1928 281 14.3
O F G L U E S I-j
N o . I-hlade from t h e last runs or cookings of imported cattle hide fleshings t h a t h a d been previously dried. No. a-Made by cooking carefully washed packer bones under pressure. KO. 3--A cattle hide glue. No. 4-LIade from packer bones a n d pieces of calfskin. S o . 5-Nade from t h e liquors obtained in boiling bones in a packing house. From Table VI1 i t is evident t h a t t h e three tests are independent of each other-perhaps because not dependent upon t h e same constituent.
-4
fiG.1-A BLOCK FOR
T€S T /NG
GLUE FIG I
a t t h e end, which is t h u s multiplied t e n times. T h e pointed pins a n d screws fit into t h e center marks on t h e ends of t h e blocks, t h e screws being adjusted until both ends of t h e lever a n d its middle pin are in t h e same line. T h e pressure upon each block was determined by a spring balance rather t h a n by calculation. The pieces were glued as follows: T h e blocks were dried i n a water oven at 65’, t h e glue solution made as previously described a n d heated t o 6 j O ; t h e halves of t h e block were held vertically over t h e glue, which was applied thoroughly with a brush; t h e blocks were t h e n fitted together a n d t h e excess of glue allowed t o drip away. T h e glued block was placed in a Vshaped form a n d t h e alignment completed b y pressing another V-shaped form upon t h e block. While
V-DRYIXG P E R I O D S A K D P R E S S U R E S VARIED^ T h e previous investigation was continued using t h e same apparatus a n d glues b u t varying t h e conditions, making some joo tests in all. Test specimens were dried 3 a n d 2 4 hrs. under pressures of I O , 2 0 , 30, 40, j o a n d I O O lbs. I t was found in every case t h a t t h e 24-hr. joint was about 3 per cent’stronger and t h a t 3 0 lbs. per sq. in. pressure gave a joint about ~j per cent stronger t h a n either t h e I O or I O O lbs. pressure. T h e exact behavior is shown in t h e curves of Fig. 11. A s u m m a r y of t h e results is given in Table V I I I . T h e glued blocks were heated t o 65’ for several hours. This was shown b y later work t o diminish t h e strength very materially. I t is much better t o let t h e m d r y in t h e open room for I O O hrs.-the humidity seems t o be without influence upon them.
TABLE VIII-AVERAGE TENSILE STRENGTHS OF GLUESI N LBS. PER SQ.IN. A--ilverage of a b o u t 100 tests f o r each glue f r o m 10-100 lbs. pressure a n d from 3-100 hours’ drying. B-Average of tests which are considered the most trustworthy. Liquid 1 2 3 4 5 glue GLUE A .............................. 3338 2443 2950 2336 1696 2093 Average of 3 highest in A , , . . . . . . . . . 3791 2721 3253 2624 2095 2175 Highestin A . . . . . . . . . . . . . . . . . . . . . 4829 5025 4170 5486 3067 2540 Lowest i n A ..................... 1893 1399 1775 1761 1308 1631 3361 3212 2972 3624 2182 2085 B..............................
VI-REVIEW
AND COSCLUSIOF~
This consisted i n verifying t h e work of t h e last t w o observers a n d in making definite directions for t h e gluing process, which requires practically a week for its execution. G L U E SOLUTION--120 g. of glue are covered with 1 f
B y C. S . Redfield. B y A. H. Whittlesey.
I 06
T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
1 5 0 cc. of water ( e . g., on Monday n i g h t ) , T h e next morning t h e blocks t o be glued are heated in a n air b a t h t o 60" C. for z hrs. Meanwhile t h e glue is warmed i n a water b a t h a n d sufficient water added t o make 300 g. of glue a n d water. When t h e z hrs. have nearly expired t h e 40 per cent glue solution is warmed in a water b a t h t o 6 0 " C., melted, a n d thoroughly stirred. H o t water should be a t h a n d t o add t o t h e water b a t h for heating t h e glue in order t h a t i t s temperature m a y be k e p t at 60" C. srzIr;G-The hot blocks are t a k e n from t h e air b a t h t w o a t a t i m e ; t h e ends are dipped in hot water a n d rubbed together. This is repeated until t h e blocks are thoroughly moist, when t h e y are dipped in t h e solution, t h e ends rubbed together, a n d set aside t o d r y in t h e air of t h e laboratory for z days. Sized joints a r e found t o be stronger t h a n unsized. G L u I x i o T h e sized blocks are again heated t o
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T h e results upon some of t h e preceding glues were as given in Table I X i n lbs. per square inch, TABLEIX-COMPARISON
RESULTSBY VARIOUSWORKZRS GLUENo. 5 Whi ttlesey (Bone-glue) Red- , GLUEKO.2 Red- WhitBone-glue Esten field (a) ( b ) (c) Esten field tlesey Average of all.. . . . . . 2443 2792 3056 2358 3888 . 1696 2730 Av. of 3 highest.. , . , . 1982 2721 3630 3902 3206 5026 1928 2095 3562 Highest ... . . . . . . , , . 2011 5025 3704 4000 3440 5920 1993 3067 3880 Lowest . . . . . . . . . . . . . . . 1782 1399 1840 2040 1020 2140 1775 1308 1760 ( a ) Dec.. 1912. ( b ) Dec., 1913. (c) Glued in April and broken 6 mos. later. S U M 31ARY
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T h e preceding work seems t o justify t h e following conclusions: I-That t h e tensile strength, jelly test and viscosity of glue bear no relation t o each other. 11-That t h e method followed for tensile strength m a y be expected t o give results with a variation of I O per cent. 111-That t h e method of testing t h e strength of glue b y measuring t h e strength which i t imparts t o bibulous paper is dependable a n d gives fairly concordant results. CHEMICAL DEPARTMENT MASSACHUSETTS INSTITUTE O R TECHXOLOGY BOSTON I _ ~ _ ~ _ _ _ _
A COMPARISON OF VARIOUS MODIFICATIONS OF THE KJELDAHL METHOD WITH THE DUMAS METHOD OF DETERMINING NITROGEN IN COAL, WITH NOTES ON ERRORS IN THE DUMAS METHOD DUE, TO NITROGEN EVOLVED FROM THE COPPER OXIDE1 By ARNOC. FIELDNER AND CARLA. TAYLOR
T h e experiments described in this paper were undert a k e n t o ascertain which modifications of t h e Kjeldah1 method are best a d a p t e d t o t h e determination of nitrogen in coal, a n d t o check t h e results if possible with t h e D u m a s gas-volumetric method. T h e latter method, although difficult a n d tedious t o operate, is generally regarded a s fundamental a n d applicable t o almost all classes of organic compounds. A series of determinations, using some of t h e best 20 30 40 5a 60 70 80 90 known of t h e various modifications of the Kjeldahl DRYING P R E S S U ~ ~ F S - ~ B S .method, was made on t h e following eight coals chosen FIG.I1 t o represent various types a n d t o range i n nitrogen 0.8 to 1.8 per cent: from 60' C., a n d t h e hot 40 per cent glue solution prepared TABLEI-DESCRIPTION OF COALS a s above. This should be close t o t h e frame where COALNo. LOCALITY BED CLASS t h e blocks are t o be dried under weights. T h e blocks Lignite 1 Morton Co., N. D . Sub-bituminous 2 Mussellshell Co., M are t a k e n from t h e air b a t h in pairs a n d t h e ends dipped Bituminous Semi-bituminous in glue until there is a fairly thick layer on each block. No. 3 Semi-bituminous Semi-bituminous T h e y are t h e n placed together b y s l i d i n g t h e end Semi-bituminous 8 Campbell Co., T e n n . . . . . . Rex Bituminous of one across t h a t of t h e other in order t o avoid entangling air bubbles, a n d with due regard t o t h e grain GENERAL PROCEDURE of t h e wood. T h e excess of glue around t h e joint A considerable q u a n t i t y of each sample was prepared is removed with a penknife. T h e blocks are placed b y pulverizing t h e air-dried coal i n a porcelain balli n t h e V-shaped frames t o secure alignment, p u t into mill t o 60 mesh a n d finer; in fact, most of t h e material t h e rack, a n d a weight of 30 Ibs. per sq. in. is applied would pass through a I O O mesh sieve. before t h e glue has a chance t o peel or dry. T h u s The general procedure in all of t h e Kjeldahl methods one block is glued before t h e next is t a k e n from t h e was essentially as follows: A I g r a m sample was diair b a t h . T h e blocks are allowed t o s t a y under presgested in a jjo cc. Kjeldahl flask with 30 cc. concensure for 24 hrs., when t h e y are removed, laid on their 1 Presented at the Spring Meeting of the American Chemical Society, sides a n d dried in t h e air of t h e laboratory for a t least Cincinnati, April 7-10. 1914, by permission of the Director of the Bureau I O O hrs. before breaking. of Mines.
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