Seb., 1919 2 " E JOUKATAL O F 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 . 135

perience as here set forth may be of nse to others work- RESULTIKG GAS mxTcRE-Thc character of the re- ing with sulfur gases. sulting gas mixiure, quantitatively considered, de-

pends more upon the initial carbon disulfide concen- CONCLUSIOSS tration than upon variation in the reaction. With

QUALITATIVE RESULTS-Combustion of carbon di- sulfide in dilute mixtures with air alrvays results in the formation of carbon dioxide, carbon monoxide, sulfur dioxide, and some residual carbon disulfide. The 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 to secondary reactions not likely to occur in the field.

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 in- creased 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.

disulfide is quite toxic to squirrels. Two per cent gas kills normal animals in less than 15 min.' The residual carbon disulfide always found must be an important

TOXICITY O F RESULTING G A S MIXTURES--Carbon

I'AKIATIONS I N THE REsuLTs-Some variation in factor in the toxicity of the exploded gases, Sulfur the reaction appears to take place even under labora- dioxide is also quite toxic but not so virulent as car- tory conditions. Inasmuch as the conditions must bon disulfide. Two per cent sulfur dioxide kills in vary much marc in the field than in the laboratory, about 4j min. Although we have conducted a great multiplication of laboratory experiments to secure many experiments with animals we have observed no greater concordance seemed unnecessary. indication that the depletion of the oxyEen or the pres-

~~

CHARACTER TKE REACTIoNS-~n 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 to z i Der cent followed Reac-

ence 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.

" " ~

tion I, and I j to 30 per cent remained undecom- AGR'C"LzURAL ExPanrMENrSTnTroN UNivnavllv 0s CILI.oRNI*

posed. B E B K ~ L B Y . C ~ ~ r a o n w m

I 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 specifi- cations. The most important of these specifications states that the fiber boards used in the construction

~~ ~~

During the past eighteen months, the Mellon In- stitute has been conducting an investigation of the Mullen and V'ebb testers and their application to this product. The results of th i s investigation have shown that the Mullen machine is not adapted to 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 an investiga- tion 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 con- sist 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 to 100.0 per cent. These faces are pasted to 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 by hydrostatic pressure. In the case of the Webb machine, the component parts are tested separately by 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 O F I N D U S T R I A L

per sq. in.l After locating this point as exactly as possible o n the new machine, the dial was then divided into equal units from o t o 600 lbs. per sq. in., based on the deflection of t he spring. This is the 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 he new machine with the Mullen in this way, because i t has been found tha t t h e Mullen tester will give reliable results when used on flat sheets of well-made, even-textured paper. As will be shown later, however, the Mullen results tend t o become erratic when the coarser texture of fiber facings and boards are encountered.

FIG. 4

I n testing a flat, single sheet on the Webb machine, -the sample is placed on the bedplate between the well and the plunger and held firmly with the clamp. This clamp is operated by a spring and cam and results in a constant pressure.2

After securing the sample in this manner, the dial is set at zero, and by turning the small handwheel the spring and plunger are moved downward inside the outer barrel as a unit until the plunger touches the

1 Keuffel and Esser’s “Ariston” Brand, calipering 0.0135 in. 2 It has been found in the case of i he Mullen machine that the results

can be varied by using different clamp pressures on the variable pressure clamp used on that machine.

A N D E & V G I N E E R I N G C H E M I S T R Y I3 5

sample. Up t o this point there has been no deflec- tion in the spring, so tha t t he dial does not begin registering until the plunger touches the sample.

At this point, the plunger’s motion ceases and con- tinued turning of t he handwheel commences t o build up compression in the spring, which compression is registered on the dial in terms of pounds per square inch. This is continued until the paper fails, when the plunger suddenly bursts through. The hand on the dial automatically stops a t the instant of rupture, since the dial is adjusted t o show only the compre,ssion in the spring.

For testing the complete corrugated board, the upper part of the instrument is slipped into the higher level in the bedplate, thus allowing the steel finger t o be exposed (Fig. 4) . This finger is shaped t Q fit exactly into one corrugation of the 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 the entire board at 0nce.l

The capacity of the tester is about 600 lbs. per sq. in., and the spring is sufficiently oversize t o have a large factor of safety. Due t o this, the deflection of the spring is a t all times within its elastic limit. Dur- ing the past twelve months, between 10,000 and 12,000 punctures have been made with one machine, and no variation has been noted in the action of the 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 the “perfect paper” used for calibration have just been repeated, using the same sample. The results agreed with the former measurements within 2 . 0 per cent, which vari- ation is no larger t han the average variation between individual punctures.

It has been found tha t the readings on the Mullen tester on fiber boards can be varied t o a considerable extent by varying the speed of the handwheel which builds up the hydrostatic pressure. Table I1 shows some typical Mullen results obtained on the same cor- rugated board by using varying wheel speeds.

TABLE II-MULL.EN TESTS WITH VARYING WHEFL SPEEDS SAMPLE No. HS175

Handwheel Average of Speed 10 Punctures Maximum Minimum

R. P. M. Lbs. Lbs. Lbs. 30 181.1 I95 147

120 192.0 209 165

I n order t o avoid this source of error in the new machine, the gearing is arranged in such a manner t h a t t he limits of speed a t which the small wheel can be turned by hand make a hardly perceptible variation in the speed a t which the plunger descends.

1 In addition to the regular model, the Webb tester is made in a pocket size. This style resembles an ordinary micrometer. The operating prin- ciple is similar to that of the larger machine, namely, a helical steel spring

In this case the spring is compressed directly by turning a knurled sleeve on the barrel and the values are read upon this barrel as in the case of a micrometer. The plunger and supporting finger are identical with those on the larger machine,

This smaller instrument has been calibrated against the 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 specifica- tion. 4 loaded box can be tested by 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 to rai!road inspectors, purchasing agents, etc.

’ actuating a steel plunger.

T H E J O U R N A L O F 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 Vol. 11, No. 2

Due t o the method of its manufacture and t o the nature of the raw materials used, fiber board usually contains many minute pieces of undigested wood and other impurities. These do not detract from the strength of the board in a shipping container, bu t when tested on the Mullen machine the soft rubber dia- phragm will invariably find any such particle in i ts square inch of area and the rupture will start a t this point. This causes an abnormally low reading and as a result the Mullen tends t o reflect the average of t he minimum values of a board instead of the true average. This may be demonstrated readily by applying the diaphragm t o an area in which a pin-hole has been made and comparing the resulting low reading with tha t obtained from another area which has no pin-hole. Table 111, illustrating this fact, shows the results of drilling holes of various sizes in the test area.

TABLE 111-DEPRESSION OF MULLEN TEST CAUSED BY DRILLING A SINGLE HOLE IN THE MULLEN TEST AREA OF SAMPLE

AVERAGB OF 10 MULLEN TESTS

Drawing Fiber Facing Fiber Facing Diameter Paper 0.012 Board 0.016 Board 0.017

of Hole In. Thick In. Thick In. Thick Inch Lbs. Lbs. Lbs. None 0.013 0.026 0.052 0.104 0.208

97 98 80 93 84 76 84 79 73 72 61 60 58 63 48 51 43 35

I n order t o determine whether the smallest of the above holes was an actual source of weakness, or only a starting point for the Mullen break, a test area was punctured with six of these holes and the Mullen dia- phragm applied. The break started a t only one hole and the other five holes were not encountered by the break. I n other words, six holes did not depress the Mullen reading more than one hole.

To avoid this source of error, the plunger of the new machine is made of metal. The small area attacked, together with the fact t ha t the face of the plunger is metallic, tends t o give a better average of the sample. Thus, a low reading will be reflected only when the plunger comes directly over an impurity. These im- purities are, with few exceptions, smaller than the Webb plunger face and therefore do not have an abnormal effect on the Webb average results. It will be seen from Table I11 tha t one small impurity in a circle of over one inch diameter is sufficient t o lower the Mul- len result, whereas the Webb plunger would make about 150 punctures in the same area without en- countering this speck.

As stated above, the two testers give similar results on the “perfect paper.” When testing fiber boards, however, the new machine usually gives higher re- sults than the Mullen and this divergence is, in gen- eral, in direct proportion t o the percentage of minute impurities in the sample.

Table IV gives some typical instances. The im- purities described above are designated ‘(screenings.”

The face of the Webb plunger has no sharp edges, and in making a puncture i t does not cut its way through the sample, but tears t he fibers apart as shown in Fig. 6 . The use of a metal plunger also insures a definite area of contact, in contrast with the area of a

rubber diaphragm, which varies under different pres- sures. TABLE IV-MULLEN AND WEBB TESTS ON FLAT SAMPLES OF VARYINQ

TEXTURE

MULLEN WEBB RESULTS RESULTS

“Perfect Paper” 0.0135 Very even 96 .9 10 97.05 10 Arena Bond 0.0033 Even 34 .0 7 33.80 10 Fiber Facing No. 205 0.017 Fairlysmooth 101.0 10 108.00 10 Fiber Facing No. 169 0.018 Screenings 86 .0 10 111.00 10 Fiber Facing No. 171 0.023 Screenings 105.0 10 123.00 10

In addition t o the puncture test, the Webb machine is fitted with attachments for measuring tensile strength, percentage elongation, and also deflection of the corrugations when under compression. These linear measurements are recorded on a small microme- ter dial, graduated in thousandths of an inch, which is geared t o the plunger in such a way tha t i t indicates and measures its downward movement.

The attachment for measuring tensile strength is not shown in Figs. 3 and 4, but consists of two clamps, one being stationary and attached t o the upper frame of the machine, while the other is fixed t o and actuated by the downward movement of the plunger in such a manner as t o give a direct, vertical pull on the test strip. This attachment is designed t o test the tensile strengths of the various components of a corrugated fiber container, such as the gummed taped joints, facing boards before and after bending, etc.

Tests on fiber sheets made in this manner indicated tha t most samples are much stronger in the “machine” direction than in the “cross” direction. Elongation tests indicated tha t the cross direction fibers often stretch from three t o five times as much as those in the machine direction under the same tension. Table V shows some typical results illustrating this point.

TABLE V-TENSILE TESTS O F TYPICAL FACING BOARDS TENSILE STRENGTH ‘/z INCH WIDTH Machine-

\ wise MACHINE DIRECTION CROSS DIRECTION Elor

Lbs. per r Lbs. per SAMPLE 1/2 In. 111. In.

No. Webb Units Width Webb Units Width 426 46 183 1 9 . 7 4 . 0

3-L 162 205 22 123 13.2 3 . 2

Due t o these facts, t he advancing Mullen diaphragm causes the cross fibers t o stretch, thus throwing the load on the machine direction fibers, which finally rupture. This very likely accounts for the fact t ha t all Mullen ruptures are invariably L‘across the grain’’ of the paper (Fig. 5 ) . Thus, i t would seem tha t a Mullen test is in reality a test of the machine direction fibers only.

In order t o study this effect, a test was made of a series of fiber facing boards having varying propor- tions of their fibers in the machine direction. These samples were similar in their other physical proper- ties. The proportion of fibers in the machine direction was determined b y tensile and elongation tests, as described elsewhere in this paper. It was found in every case tha t the samples having the greatest pro- portion of fibers in the 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

Mullen results than the samples whose fibers were more evenly distributed in all directions. A high hIu1- len test in this connection is not a true indication of strength, because, owing t o the method of its manu- facture, a loaded corrugated box has, with very few exceptions. cight of its twelve edges exerting tension UIOSS the machine direction fibers.

A N D E N G I N E E R I N G C H E M I S T R Y 1 3 7

Fro S-TYPICAL RRSAZ MADS BY MULLEN T r i s l E ~ ON I00 : B P I I ; ? ~ FACING. ACTUAL S ~ Z E

In order to 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 to increase the proportion of the cross-direction fibers. The only way to do this without increasing the thickness of the paper is to decrease the excess of fibers in the machine direction. The result is a lowering of the machine direction ten- sile strength, but a raising of the cross-direction tensile strength. Comparison of the breaks made by the two machines (Figs. j and 6) shows that the tendency of the round metallic Webb plunger is t o take into ac- count 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 by 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 by 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 to 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 in the first in- stance 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 to make actual tensile tests.

PTO. ~ T ~ ~ I ~ ~ ~ naEm M A ~ S WLW TBSTSH ,>N ioi) I . ~ . nnBa FAcnra x 12

CONCLUSIONS

The Webb tester and its various attachments have been carefully investigated in this laboratory. I n making these tests, several hundred samples of cor- rugated board, representing practically all the varieties known to the trade, have been collected. These sam- ples were all studied and the data tabulated as fol- lows:

I--Raw material used (as revealed by the micro- scope).

z-Physical properties, such as bending quality, thickncss, etc.

3-Degree of water-proofing, if any. 4-Degree to which fibers had been “felted” or

“formed,” as indicated by tensile strength and elonga- tion 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 to adapt the Mullen machine to testing corrugated fiber products. No practical method was found for doing this.

S U M X A R Y

I-The Webb tester is correctly designed and con- structed from a mechanical standpoint.

11-The Webb tester gives a more accurate meas- urement of the value of paper products (especially cor- rugated fiber board) than is possible by the use of the Mullen tester.

138 T H E J O U R N A L O F 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 Val. 11, KO. 2

111-In addition t o the puncture test, the Webb machine may be used for tensile tests, elongation tests, and compression tests. The tensile test, especially when “across the grain,” is an 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 to 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.

MELLON INSTITUTB OB INDUSTRIAL RESEARCH UNIVERSITY OF PITTSBURGH. PITTSBURGH, PA.

LEAD IN PHARMACEUTICAL ZINC OXIDE By W. D. COLLINS AND W. F. CLARKE

Received July 25, 1918

Soon after the outbreak of the present war, difficulty was experienced in obtaining pharmaceutical zinc oxide which would meet the requirements of the Ulzited States Pharmacopoeia. When the matter was first considered, the statement was made tha t zinc oxide of the required purity was very easy to obtain. It was even stated tha t material bought for use as a pigment in painting might be more nearly free from lead than 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 tha t analysis of such samples of zinc oxide as could be procured on the market a t tha t time indicated tha t practically all the zinc oxide obtainable contained more lead than was permitted by the U . S. P. test. Some manufacturers a t this time stated on the labels tha 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 tha t all samples of pharmaceutical zinc oxide should be tested for lead.

In order to learn whether it would be possible to obtain zinc oxide reasonably free from lead, samples were obtained on the market and from manufacturers, and the question was taken up with

the U. S. Geological Survey and with manufacturers of zinc oxide. It was learned from Mr. C. E. Sieben- thal of the U. S. Geological Survey tha t one company producing zinc in the United States owned a mine which contained no lead minerals and, therefore, should be able to produce zinc oxide free from lead. It would seem probable tha t zinc oxide made from electrolytic zinc should be free from lead. It was learned from manufacturers tha t zinc oxide was being made according to both of these principles, and tha t the products contained much less lead than the amount necessary to respond to the U . S. P. test for heavy metals.

TEST FOR LEAD I N ZINC OXIDE BY THE U. S. P. TEST FOR HEAVY MET\ALS

I n order to determine the sensitiveness of the U . S. P. test for lead in zinc oxide, two series of experiments were conducted entirely independently in order to establish the limits of sensitiveness. Different quanti- ties of lead from a solution of lead nitrate were made up with zinc oxide and hydrochloric acid so as to 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.), the hydrogen sulfide used was made according to the directions of the P h a r m a - copoeia. I n the other series of tests (W. D. e.), the hydrogen sulfide used was prepared in the ordinary manner by the use of hydrochloric acid and ferrous sulfide and the gas was washed through water. No difference could be detectcd in the results by the two methods.

It was found tha t a sample of zinc oxide might con- tain as much as 0.05 per cent lead and fail to respond to 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 to the test.

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.

SAMPLE NO. 1 1 7 . . 1 1 8 . . . 119 . . . 133. . . 134 . . . 137 . . . 130 . . , 148 . . . 158 . . . 1 5 9 . . . 1 5 5 . . . 1 7 8 . . . 1 8 7 . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136. .................................

Received 1-13-17 1-16-17 1-16-17 84-17 8-4-1 7 8-6- 1 7 1915 9-27-1 7 11-28-17 11-29-17 11-5-17 2-1-18 2-4- 1 8

Dealer A B A D F B K I I I C H I,

TABLE I-ZINC Producer or

Manufacturer ?

d E G C H I I I K I I

OXIDE Lead

Per cent 0.25 0.036 0 .25 0 . 1 9 0 . 1 9 0 .26 0.041 0.006 0.004 0.008 0.013 0.004 0.008

u. s. P. Test +

0 f

+ 0 0 0 0 0 0 0

+

METALLIC ZINC 1914 . . M 0.026 . . 1917 N M probably 0 .094 . . 9-26-17 .. K 0.012 . .

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 at 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

PIGMENT ZINC OXIDE 8-4- 1 7 0 . . 0 . 1 3 Trace About 22 per cent barium sulfate 8-4-1 7 P . . 5 3 . 2 Heavy

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. He 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.