Seb., 1919
2 " E JOUKATAL OF I.VDl~STRI.4L A Y D E S C I S E E R I N G C H E M I S T R I .
perience as here set forth may be of nse to others working with sulfur gases.
R E S U L T I K G G A S mxTcRE-Thc character of the resulting gas mixiure, quantitatively considered, depends more upon the initial carbon disulfide concentration than upon variation in the reaction. With 2',12 per cent carbon disulfide the oxygen content of the air is reduced from approximately 2 0 to about 15 per cent, and the carbon dioxide increased to about I per cent; carbon monoxide and carbon disulfide approach, but seldom exceed, I per cent, but sulfur dioxide appears t o the amount of about 4 per cent. TOXICITY O F RESULTING G A S MIXTURES--Carbon disulfide is quite toxic t o squirrels. Two per cent gas kills normal animals in less than 15 min.' The residual carbon disulfide always found must be a n important factor in the toxicity of the exploded gases, Sulfur dioxide is also quite toxic but not so virulent as carbon disulfide. Two per cent sulfur dioxide kills in about 4j min. Although we have conducted a great many experiments with animals we have observed no indication that the depletion of the oxyEen or the presence of small quantities of carbon dioxide contributes materially to death. We ascribe some effect t o the small amounts of carbon monoxide but death would probably ensue in approximately the same time in the absence Of this gas.
CONCLUSIOSS Q U A L I T A T I V E RESULTS-Combustion of carbon disulfide in dilute mixtures with air alrvays results in the formation of carbon dioxide, carbon monoxide, sulfur dioxide, and some residual carbon disulfide. T h e formation of sulfur trioxide does not appear to take place. The formation of elemental sulfur was not observed, but sulfides were indicated in several experiments when metals were present. TVe ascribe this sulfide formation t o secondary reactions not likely t o occur in the field.
I'AKIATIONS I N THE REsuLTs-Some variation in the reaction appears t o take place even under laboratory conditions. Inasmuch as the conditions must vary much marc in the field than in the laboratory, multiplication of laboratory experiments t o secure greater concordance seemed unnecessary.
~~
the experiments in the glass container which are regarded as the more reliable, from 4o to 6o per cent (in round numbers) of the initial ,amount of carbon disulfide followed Reaction 11. from 2 i t o "z "i Der cent followed Reaction I, and I j to 30 per cent remained undecomposed. CHARACTER
135
T K E REACTIoNS-~n
~
I
AGR'C"LzURAL
ExPanrMENrSTnTroN
UNivnavllv 0s CILI.oRNI* B E B K ~ L B YC. ~ ~ r a o n w m
LABORATORY AND PLANT ~~
THE WEBB PAPER TESTER-A NEW INSTRUMENT FOR TESTING CORRUGATED FIBER BOARDS By J. D. M_ILUOLU$ON Received October 7, 1918
Corrugated fiber boxes, when used as containers for freight shipments, must meet certain railroad specifications. The most important of these specifications states that the fiber boards used in the construction
..
~~
During the past eighteen months, the Mellon Institute has been conducting an investigation of the Mullen and V'ebb testers and their application t o this product. The results of t h i s investigation have shown t h a t the Mullen machine is not adapted t o testing a corrugated fiber board, while the Webb machine gives a much more accurate value of the strength of such a board.
Y
and summary of the results obtained in a n investigation of this tester carried out a t the Mellon Institute. Corrugated fiber boxes are made of what is known as double-faced corrugated board. These faces consist of tough fiber board ranging from 0.016 in. t o 0.030 in. in thickness, and are made of a mixture of waste paper and new fiber. The percentage of the latter depends upon the resulting strength desired and may vary from 0.0 t o 100.0 per cent. These faces are pasted t o a corrugated "liner" of strawboard about 0.009 in. thick to make the finished board (Fig. I ) .
FIG. 1
The fundamental difference between the two testers is that in the case of the Mullen t h e board as a whole must first be firmly clamped in the machine, thus crushing the corrugations, and a puncture test of the board is then made. The puncturing medium is a rubber diaphragm actuated b y hydrostatic pressure. In the case of the Webb machine, the component parts are tested separately b y means of a metallic plunger actuated by a compressed helical steel spring. L L O C . 'ti.
.!,
T H E J O U R N A L OF I N D U S T R I A L A N D E&VGINEERING C H E M I S T R Y
I3 5
sample. Up t o this point there has been no deflection in t h e spring, so t h a t t h e dial does not begin registering until the plunger touches t h e sample. At this point, t h e plunger’s motion ceases and continued turning of t h e handwheel commences t o build up compression in t h e spring, which compression is registered on t h e dial in terms of pounds per square inch. This is continued until t h e paper fails, when the plunger suddenly bursts through. The hand on t h e dial automatically stops a t t h e instant of rupture, since t h e dial is adjusted t o show only t h e compre,ssion in t h e spring. For testing t h e complete corrugated board, t h e upper part of the instrument is slipped into t h e higher level in t h e bedplate, thus allowing t h e steel finger t o be exposed (Fig. 4 ) . This finger is shaped t Q fit exactly into one corrugation of t h e strawboard. By this means, each facing must be tested separately. The machine is so designed as t o make i t impossible t o puncture t h e entire board at 0nce.l The capacity of t h e tester is about 600 lbs. per sq. in., and t h e spring is sufficiently oversize t o have a large factor of safety. Due t o this, t h e deflection of t h e spring is a t all times within its elastic limit. During t h e past twelve months, between 10,000and 12,000 punctures have been made with one machine, and no variation has been noted in the action of t h e spring. Samples used in these tests have ranged from tissue paper t o solid fiber board testing slightly over j o o Ibs. per sq. in. Tests made one year ago on t h e “perfect paper” used for calibration have just been repeated, using t h e same sample. The results agreed with t h e former measurements within 2 . 0 per cent, which variation is no larger t h a n the average variation between individual punctures. It has been found t h a t t h e readings on t h e Mullen tester on fiber boards can be varied t o a considerable extent by varying t h e speed of t h e handwheel which builds u p t h e hydrostatic pressure. Table I1 shows some typical Mullen results obtained on the same corrugated board b y using varying wheel speeds.
per sq. in.l After locating this point as exactly as possible o n the new machine, t h e dial was then divided i n t o equal units from o t o 600 lbs. per sq. in., based on t h e deflection of t h e spring. This is t h e usual method of calibrating helical springs, such as spring balances, drawbar springs on railroad dynamometer cars, etc. I t is possible t o calibrate t h e new machine with t h e Mullen in this way, because i t has been found t h a t t h e Mullen tester will give reliable results when used o n flat sheets of well-made, even-textured paper. As will be shown later, however, t h e Mullen results tend t o become erratic when t h e coarser texture of fiber facings and boards are encountered.
TABLEII-MULL.EN TESTSWITH VARYINGWHEFL SPEEDS SAMPLE No. HS175 Handwheel Average of Speed
R. P. M. 30 120
Keuffel and Esser’s “Ariston” Brand, calipering 0.0135 in. It has been found in t h e case of i h e Mullen machine t h a t the results can be varied by using different clamp pressures on t h e variable pressure clamp used on that machine. 1
2
Maximum Lbs. I95 209
Minimum Lbs. 147
165
I n order t o avoid this source of error in t h e new machine, t h e gearing is arranged in such a manner t h a t t h e limits of speed a t which t h e small wheel can be turned by hand make a hardly perceptible variation in the speed a t which t h e plunger descends.
FIG.4
I n testing a flat, single sheet on the Webb machine, -the sample is placed on the bedplate between t h e well and t h e plunger and held firmly with t h e clamp. This clamp is operated b y a spring and cam and results in a constant pressure.2 After securing t h e sample in this manner, t h e dial is set at zero, and by turning t h e small handwheel t h e spring and plunger are moved downward inside t h e outer barrel as a unit until t h e plunger touches t h e
10 Punctures Lbs. 181.1 192.0
’
1 In addition to the regular model, the Webb tester is made in a pocket size. This style resembles a n ordinary micrometer. T h e operating principle is similar t o t h a t of the larger machine, namely, a helical steel spring actuating a steel plunger. I n this case the spring is compressed directly b y turning a knurled sleeve on the barrel and the values are read upon this barrel as in the case of a micrometer. T h e plunger and supporting finger are identical with those on the larger machine, This smaller instrument has been calibrated against t h e larger one, and while not so sensitive is valuable as a preliminary, or minimum tester, since i t will quickly indicate whether a box is above or below its specification. 4 loaded box can be tested b y cntting a small slit in one of the flaps and inserting the steel finger. With this instrument, the box can be tested in siiu without disturbing its contents. This model is compact and inexpensive and could be supplied t o rai!road inspectors, purchasing agents, etc.
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 CHEMISTRY Due t o the method of its manufacture and t o t h e nature of t h e raw materials used, fiber board usually contains many minute pieces of undigested wood and other impurities. These do not detract from t h e strength of the board in a shipping container, b u t when tested on the Mullen machine the soft rubber diaphragm will invariably find any such particle in its square inch of area and t h e rupture will start a t this point. This causes an abnormally low reading and as a result the Mullen tends t o reflect t h e average of t h e minimum values of a board instead of the true average. This may be demonstrated readily b y applying t h e diaphragm t o an area in which a pin-hole has been made and comparing t h e resulting low reading with t h a t obtained from another area which has no pin-hole. Table 111, illustrating this fact, shows t h e results of drilling holes of various sizes in t h e test area. TABLE111-DEPRESSIONO F MULLENTEST CAUSED BY DRILLING A SINGLE HOLEIN THE MULLENTEST AREAOF SAMPLE AVERAGB OF 10 MULLENTESTS Diameter of Hole Inch
None
0.013 0.026 0.052 0.104 0.208
Drawing Paper 0.012 In. Thick Lbs. 97 93 84 72 58 51
Fiber Facing Fiber Facing Board 0.016 Board 0.017 In. Thick In. Thick Lbs. Lbs. 98 80 84 76 79 73 61 60 63 48 43 35
I n order t o determine whether t h e smallest of t h e above holes was an actual source of weakness, or only a starting point for t h e Mullen break, a test area was punctured with six of these holes and t h e Mullen diaphragm applied. T h e break started a t only one hole and t h e other five holes were not encountered b y t h e break. I n other words, six holes did not depress t h e Mullen reading more t h a n one hole. T o avoid this source of error, t h e plunger of t h e new machine is made of metal. The small area attacked, together with t h e fact t h a t the face of t h e plunger is metallic, tends t o give a better average of t h e sample. Thus, a low reading will be reflected only when t h e plunger comes directly over an impurity. These impurities are, with few exceptions, smaller t h a n t h e Webb plunger face and therefore do not have a n abnormal effect on t h e Webb average results. It will be seen from Table I11 t h a t one small impurity in a circle of over one inch diameter is sufficient t o lower t h e Mullen result, whereas the Webb plunger would make about 1 5 0 punctures in the same area without encountering this speck. As stated above, t h e two testers give similar results on t h e “perfect paper.” When testing fiber boards, however, t h e new machine usually gives higher results t h a n t h e Mullen and this divergence is, in general, in direct proportion t o the percentage of minute impurities in t h e sample. Table I V gives some typical instances. The impurities described above are designated ‘(screenings.” T h e face of t h e Webb plunger has no sharp edges, and in making a puncture i t does not cut its way through t h e sample, but tears t h e fibers apart as shown in Fig. 6 . The use of a metal plunger also insures a definite area of contact, in contrast with t h e area of a
Vol.
11,
No.
2
rubber diaphragm, which varies under different pressures. TABLEIV-MULLEN
AND
WEBB TESTS
ON
TEXTURE
FLAT SAMPLES OF VARYINQ MULLEN RESULTS
“Perfect Paper” Arena Bond Fiber Facing No. 205 Fiber Facing No. 169 Fiber Facing No. 171
0.0135 0.0033 0.017 0.018 0.023
Very even Even Fairlysmooth Screenings Screenings
96.9 34.0 101.0 86.0 105.0
10
7 10 10 10
WEBB RESULTS
97.05 33.80
108.00
111.00 123.00
10 10 10 10 10
In addition t o t h e puncture test, t h e Webb machine is fitted with attachments for measuring tensile strength, percentage elongation, and also deflection of t h e corrugations when under compression. These linear measurements are recorded on a small micrometer dial, graduated in thousandths of a n inch, which is geared t o t h e plunger in such a way t h a t i t indicates and measures its downward movement. The attachment for measuring tensile strength is not shown in Figs. 3 and 4, b u t consists of two clamps, one being stationary and attached t o t h e upper frame of t h e machine, while t h e other is fixed t o and actuated b y t h e downward movement of t h e plunger in such a manner as t o give a direct, vertical pull on t h e test strip. This attachment is designed t o test t h e tensile strengths of t h e various components of a corrugated fiber container, such as t h e gummed taped joints, facing boards before and after bending, etc. Tests on fiber sheets made in this manner indicated t h a t most samples are much stronger in t h e “machine” direction t h a n in t h e “cross” direction. Elongation tests indicated t h a t the cross direction fibers often stretch from three t o five times as much as those in t h e machine direction under t h e same tension. Table V shows some typical results illustrating this point. TABLEV-TENSILE TESTS O F TYPICALFACINGBOARDS TENSILESTRENGTH ‘/z INCHWIDTH Machine\ wise MACHINEDIRECTION CROSSDIRECTION Elor Lbs. per Lbs. per r SAMPLE 1/2 In. 111. In. No. Webb Units Width Webb Units Width 46 183 19.7 4.0 426 3-L 162 205 22 123 13.2 3.2
Due t o these facts, t h e advancing Mullen diaphragm causes t h e cross fibers t o stretch, thus throwing t h e load on t h e machine direction fibers, which finally rupture. This very likely accounts for t h e fact t h a t all Mullen ruptures are invariably L‘across t h e grain’’ of t h e paper (Fig. 5 ) . Thus, i t would seem t h a t a Mullen test is in reality a test of t h e machine direction fibers only. In order t o study this effect, a test was made of a series of fiber facing boards having varying proportions of their fibers in t h e machine direction. These samples were similar in their other physical properties. The proportion of fibers in t h e machine direction was determined b y tensile and elongation tests, as described elsewhere in this paper. It was found in every case t h a t t h e samples having t h e greatest proportion of fibers in t h e machine direction showed higher 1
Feb., 1919
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
137
Mullen results than the samples whose fibers were more evenly distributed in all directions. A high hIu1len test in this connection is not a true indication of strength, because, owing t o the method of its manufacture, a loaded corrugated box has, with very few exceptions. cight of its twelve edges exerting tension UIOSS the machine direction fibers.
Fro S-TYPICAL RRSAZ MADSB Y MULLEN T r i s l E ~ON I00 FACING.ACTUALS ~ Z E
:B
P I I ; ? ~ PTO. ~
I n order t o make a good shipping container, the fibers making up the structure of a liox should be “felted” in all directions. The above tests show that t o do this, it is necessary t o increase the proportion of the cross-direction fibers. The only way t o do this without increasing the thickness of the paper is t o decrease the excess of fibers in the machine direction. The result is a lowering of the machine direction tensile strength, but a raising of the cross-direction tensile strength. Comparison of the breaks made b y the two machines (Figs. j and 6) shows t h a t the tendency of the round metallic Webb plunger is t o take into account all of the fibers regardless of their direction. These variations in the tensile strength of a fiber board (depending upon the direction in which the test is made) are emphasized b y the use of a wedge-shaped plunger in place of the round plunger mentioned above. This plunger has a rounded rectangular face 0.10 in. long b y 0.07Xjq in wide and gives the same readings as the round plunger and the Mullen tester on the “perfect paper” described above. When substituted. however, for the round plunger and applied t o fiber boards, fabrics, etc. (which have variations in tensile strength depending upon the direction of the test), the action of this wedge plunger is very marked. Thus, when the plunger is applied pnrallel t o the machine direction, a much lower reading is repistered than when applied a t right angles t o this direction. This action is explained by the fact that i n the first instance the plunger’s tendency is to cut only the weaker transverse fibers (or woof threads), while in the second instance the strong, machine-direction fibers (or warp threads) are cut. This wedge plunger, thcrcfore, offers a ready means of determining the minimum strength of a sample when it is not desirable t o make actual tensile tests.
T naEm ~M A ~ S ~ WLW FAcnra x 12
TBSTSH I ,>N ~ ioi)
I . ~ nnBa . ~
CONCLUSIONS
The Webb tester and its various attachments have been carefully investigated in this laboratory. I n making these tests, several hundred samples of corrugated board, representing practically all the varieties known t o the trade, have been collected. These samples were all studied and the data tabulated as follows: I--Raw material used (as revealed by the microscope). z-Physical properties, such as bending quality, thickncss, etc. 3-Degree of water-proofing, if any. 4-Degree t o which fibers had been “felted” or “formed,” as indicated b y tensile strength and elongation in machine and cross directions. j-Appearance (impurities, “screcnings,” etc.). 6-Certified strength. 7-Actual Mullen tests of (e) Components before assembling. ( 6 ) Finished board. X.--.lctnal Webb tests. Previous to the invention of the new tester, this laboratory had devoted nearly a year t o attempting t o adapt the Mullen machine t o testing corrugated fiber products. No practical method was found for doing this. SUMXARY
I-The Webb tester is correctly designed and constructed from a mechanical standpoint. 11-The Webb tester gives a more accurate measurement of the value of paper products (especially corrugated fiber board) than is possible by the use of the Mullen tester.
~
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 CHEMISTRY
138
111-In addition t o the puncture test, the Webb machine may be used for tensile tests, elongation tests, a n d compression tests. The tensile test, especially when “across the grain,” is a n important index of the value of a fiber box as a shipping container. This “across the grain” value may also be found more quickly by a puncture test, using the “wedge” plunger. IV-The pocket-size model makes i t possible t o test corrugated boxes under conditions which are impossible a t present. V-Besides corrugated products, the Webb machine can be used for testing many other flat substances, such as paper, cardboard, * “solid fiber” boards, gummed tape, fabrics, etc. MELLONINSTITUTBOB INDUSTRIAL RESEARCH OF PITTSBURGH. PITTSBURGH, PA. UNIVERSITY
By W. D. COLLINSAND W. F. CLARKE Received July 25, 1918
Soon after the outbreak of t h e present war, difficulty was experienced in obtaining pharmaceutical zinc oxide which would meet the requirements of the Ulzited States Pharmacopoeia. When t h e matter was first considered, the statement was made t h a t zinc oxide of the required purity was very easy t o obtain. It was even stated t h a t material bought for use as a pigment in painting might be more nearly free from lead t h a n a certain sample of pharmaceutical zinc oxide which contained about 0 . 2 per cent of lead. Mr. C. L. Black of the Philadelphia Station of the Bureau of Chemistry reported in May 1917 t h a t analysis of such samples of zinc oxide as could be procured on the market a t t h a t time indicated t h a t practically all the zinc oxide obtainable contained more lead t h a n was permitted by the U . S. P . test. Some manufacturers a t this time stated on the labels t h a t the zinc oxide sold by them contained heavy metals slightly in excess of the U . S . P. limit. Prof. C . H. La Wall’ published an article calling attention t o this matter and made the suggestion t h a t all samples of pharmaceutical zinc oxide should be tested for lead. I n order t o learn whether it would be possible t o obtain zinc oxide reasonably free from lead, samples were obtained on the market and from manufacturers, and the question was taken up with Received 1-13-17 ................................. 1 1 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-16-17 1-16-17 119... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84-17 133.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-4-1 7 134... 8-6- 1 7 137 . . . 1915 130.., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-27-1 7 148... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-28-17 158... ............................... 11-29-17 1 5 9 . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-5-17 1 5 5 . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1-18 1 7 8 . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4- 18 187.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
NO. 117
11,
KO.2
the U. S. Geological Survey and with manufacturers of zinc oxide. It was learned from Mr. C. E. Siebenthal of the U. S. Geological Survey t h a t one company producing zinc in the United States owned a mine which contained no lead minerals and, therefore, should be able t o produce zinc oxide free from lead. It would seem probable t h a t zinc oxide made from electrolytic zinc should be free from lead. It was learned from manufacturers t h a t zinc oxide was being made according t o both of these principles, and t h a t the products contained much less lead t h a n t h e amount necessary t o respond t o the U . S. P. test for heavy metals. TEST F O R LEAD I N ZINC OXIDE BY THE U. S . P. T E S T F O R H E A V Y MET\ALS
LEAD IN PHARMACEUTICAL ZINC OXIDE
SAMPLE
Val.
Dealer A B A D
F
B
K
I
I
I C
H I,
..
149 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1914 1917 9-26-17
N
135 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136. .................................
8-4- 1 7 8-4-1 7
0
..
P
I n order t o determine t h e sensitiveness of the U . S. P. test for lead in zinc oxide, two series of experiments were conducted entirely independently in order t o establish the limits of sensitiveness. Different quantities of lead from a solution of lead nitrate were made up with zinc oxide and hydrochloric acid so as t o give the concentrations of zinc and acid prescribed by the U.’S. P. for the test for heavy metals. I n one series of tests (W. F. C.), t h e hydrogen sulfide used was made according t o t h e directions of t h e P h a r m a copoeia. I n t h e other series of tests (W. D. the hydrogen sulfide used was prepared in the ordinary manner by the use of hydrochloric acid a n d ferrous sulfide and the gas was washed through water. No difference could be detectcd in the results by t h e two methods. It was found t h a t a sample of zinc oxide might contain as much as 0.05 per cent lead and fail t o respond t o the test for heavy metals. I n some cases the test would be obtained and in others it would fail. When the sample contained as much as 0.I per cent, a positive test was always obtained and with any amount greater than 0.05 per cent there was rarely any doubt about the response t o the test.
e.),
SAMPLES
A number of samples of zinc oxide were purchased a t various drug stores. Some samples were furnished by manufacturers and others were obtained from dealers through the regular purchasing office of the Bureau.
TABLEI-ZINC OXIDE Producer or Lead Manufacturer Per cent ? 0.25 0.036 0.25 0.19 E 0.19 G 0.26 C 0.041 H 0.006 I 0.004 I I 0.008 0.013 K I 0.004 0.008 I METALLIC ZINC M 0.026 M probably 0.094 K 0.012 PIGMENTZINCOXIDE 0.13 53.2
d
....
u. s. P. Test
0 0
Remarks Purchased at local drug store Purchased at local drug store Purchased at local drug store Purchased at local drug store Purchased at local drug store Purchased a t local drug store From Bureau stock of reagents Show sample from office of manufacturer Sample sent by manufacturer Sample sent by manufacturer Purchased by Bureau Supply Office Purchased by Bureau Supply Office Purchased by Bureau Supply Office
.. .. ..
Analysis on label lead 0.01 per cent Analysis on label: lead none Sample furnished by manufacturer
+ 0 f
++
0 0 0 0
0
Trace Heavy
About 22 per cent barium sulfate
1 Am. J. Phaum., 89 (1917), 353-5. In a later article (Ibid., 90 (1918), 499). Professor La Wall notes that U . S.P. zinc oxide is now on the market. H e proposes tests for lead which will detect 0.03 per cent PbO in zincoxide, while the present U . S. P test under the best conditions will detect 0.05 per cent.
